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Currently I'm reading She Has Her Mother's Laugh: The Powers, Perversions, and Potential of Heredity, a fascinating book about heredity by the popular science author Carl Zimmer.
While reading this I came across this following passage, which bothers me.
It also meant that the inheritance of acquired traits - taken as a fact by Hippocrates, Lamarck, and Darwin alike - was impossible.
~ Chapter 2: Traveling Across the Face of Time
I've read Darwin's The Origin of Species, and a fair bit of other stuff on Evolutionary Biology, and as far as I know Darwin clearly opposed the idea of Lamarckian heredity. Which is why I was quite surprised to see this, from Zimmer, who's a very highly reputed author. How can he make such an obvious mistake, or is there something more to it than I know? Did Darwin ever agree with some form of Lamarckian heredity?
Here's the passage of the book where it appears, for context.
I wrote to Carl Zimmer, and he replied within two hours. That's pretty cool!
So I thought I'd put everything I learned about this here as an answer with all the links, and if you guys have more to add, feel free to post more answers.
My Original Email:
Currently I'm reading She Has Her Mother's Laugh, which is a fascinating book, and I'm thoroughly hooked. However, while reading it, I came across this passage that troubled me. The bit in question is in Chapter 2: Traveling Across the Face of Time.
"It also meant that the inheritance of acquired traits - taken as a fact by Hippocrates, Lamarck, and Darwin alike - was impossible."
From what I've read on the subject over the years, almost unanimously people agree that Darwin opposed the idea of Lamarckian heredity. I thought that Darwin's idea is that small modifications arising from random mutations (although he didn't know about DNA and genes at the time), if beneficial, were retained and accumulated over the generations resulting in new species. But is it not the case? Did actually Darwin subscribe to the idea of Lamarckian heredity?
I did a little bit of research on this, and found some conflicting and confusing information.
To start with, I've read Darwin's Origin of Species and though I remembered him opposing the idea, so I searched through the book again and found the following para.
Thus, as I believe, the wonderful fact of two distinctly defined castes of sterile workers existing in the same nest, both widely different from each other and from their parents, has originated. We can see how useful their production may have been to a social community of insects, on the same principle that the division of labour is useful to civilised man. As ants work by inherited instincts and by inherited tools or weapons, and not by acquired knowledge and manufactured instruments, a perfect division of labour could be effected with them only by the workers being sterile; for had they been fertile, they would have intercrossed, and their instincts and structure would have become blended. And nature has, as I believe, effected this admirable division of labour in the communities of ants, by the means of natural selection. But I am bound to confess, that, with all my faith in this principle, I should never have anticipated that natural selection could have been efficient in so high a degree, had not the case of these neuter insects convinced me of the fact. I have, therefore, discussed this case, at some little but wholly insufficient length, in order to show the power of natural selection, and likewise because this is by far the most serious special difficulty, which my theory has encountered. The case, also, is very interesting, as it proves that with animals, as with plants, any amount of modification in structure can be effected by the accumulation of numerous, slight, and as we must call them accidental, variations, which are in any manner profitable, without exercise or habit having come into play. For no amount of exercise, or habit, or volition, in the utterly sterile members of a community could possibly have affected the structure or instincts of the fertile members, which alone leave descendants. I am surprised that no one has advanced this demonstrative case of neuter insects, against the well-known doctrine of Lamarck.
If you read the last few sentences, Darwin says "accumulation of numerous, slight, and as we must call them accidental, variations,… " which to me indicates he's referring to random mutations in genes even though he didn't know what genes were. Furthermore, a little later, "For no amount of exercise, or habit, or volition, in the utterly sterile members of a community could possibly have affected the structure or instincts of the fertile members, which alone leave descendants." and "I am surprised that no one has advanced this demonstrative case of neuter insects, against the well-known doctrine of Lamarck."
To me this clearly indicates he was opposed to the idea of Lamarckian heredity. Could you please explain a little bit more about your stance? I'd love to hear the different viewpoint and the reason(s) behind it.
Since I was curious about this, I posted the same question on StackExchange biology forum.
One of the users pointed me to an article by Michael T. Ghiselin who seems to be in agreement with you regarding the matter.
While some of his points about textbook authors misunderstanding Lamarckian heredity sounds fair and valid, I can't quite see how he came to the conclusion that Darwin agreed with Lamarck. The passage he points to (Lamarck was the first man whose conclusions… ") doesn't say anything about Darwin agreeing with Lamarck about acquired traits being passed down the generations.
In Wiki page about Pangenesis, the following is mentioned just as you have in your book.
"Darwin thought that environmental effects that caused altered characteristics would lead to altered gemmules for the affected body part. The altered gemmules would then have a chance of being transferred to offspring, since they were assumed to be produced throughout an organisms life.2 Thus, pangenesis theory allowed for the Lamarckian idea of transmission of characteristics acquired through use and disuse. Accidental gemmule development in incorrect parts of the body could explain deformations and the 'monstrosities' Darwin cited in Variation."
Which indeed supports your viewpoint, but to me that seems like a direct contradiction to Darwin's own words in Origin of Species.
So which of it is true? Or, since Pangenesis theory came after he published Origin, did he change his mind later?
Carl Zimmer's reply:
Thanks for your email. I've also had to struggle to work out Darwin's views about Lamarck--they were complicated and changed over his career. Basically, the more Darwin thought about heredity, the more he warmed up to the possibility of the inheritance of acquired characters. I've attached a few good papers that may be of interest.
Best wishes, Carl Zimmer
Papers Referred by Carl Zimmer:
Gemmules and Elements: On Darwin's and Mendel's Concepts and Methods in Heredity.
Lamarck, Evolution, and the Inheritance of Acquired Characters.
orgThe Early History of the Idea of the Inheritance of Acquired Characters and of Pangenesis.
I haven't read those papers yet, will do so when I find time and hopefully it will shed some more light on it.
So, I'm still not quite sure about the issue, but I do think Carl Zimmer's point of view is fair enough, that it is possible Darwin's views evolved over time. Particularly, given that nobody knew what exactly even heredity means at the time, it's possible that Darwin thought it cannot just be ruled out. Besides doesn't seem like he was out campaigning for the idea, rather allowed for it with his Pangenesis hypothesis.
After all, Darwin's theory was about how small modifications accumulated over time leads to species change, not how those changes occurred in the first place. So, while it turned out to be untrue, if there was a mechanism in which experiences could be stored in the unit that transmitted heredity, you can probably incorporate that into Darwin's theory of evolution. That probably was a line of thought Darwin had.
The Institute for Creation Research
The racism of evolution theory has been documented well and widely publicized. It is known less widely that many evolutionists, including Charles Darwin, also taught that women are biologically inferior to men. Darwin's ideas, including his view of women, have had a major impact on society. In a telling indication of his attitude about women (just before he married his cousin, Emma Wedgewood), Darwin listed the advantages of marrying, which included: ". . . constant companion, (friend in old age) who will feel interested in one, object to be beloved and played with&mdashbetter than a dog anyhow&mdashHome, and someone to take care of house . . ." (Darwin, 1958:232,233).
Darwin reasoned that as a married man he would be a "poor slave, . . . worse than a Negro," but then reminisces that, "one cannot live the solitary life, with groggy old age, friendless . and childless staring in one's face. " Darwin concludes his discussion on the philosophical note, "there is many a happy slave" and shortly thereafter, married (1958:234).
Darwin concluded that adult females of most species resembled the young of both sexes and from this and the other evidence, "reasoned that males are more evolutionarily advanced than females" (Kevles, 1986:8). Many anthropologists contemporary to Darwin concluded that "women's brains were analogous to those of animals," which had "overdeveloped" sense organs "to the detriment of the brain" (Fee, 1979:418). Carl Vogt, a University of Geneva natural history professor who accepted many of "the conclusions of England's great modern naturalist, Charles Darwin," argued that "the child, the female, and the senile white" all had the intellect and nature of the "grown up Negro" (1863:192). Many of Darwin's followers accepted this reasoning, including George Romanes, who concluded that evolution caused females to become, as Kevles postulated:
. . . increasingly less cerebral and more emotional. Romanes . . . shared Darwin's view that females were less highly evolved than males&mdashideas which he articulated in several books and many articles that influenced a generation of biologists. Romanes apparently saw himself as the guardian of evolution, vested with a responsibility to keep it on the right path. . . . University of Pennsylvania . . . paleontologist Edward Drinker Cope wrote that male animals play a "more active pan in the struggle for existence," and that all females, as mothers, have had to sacrifice growth for emotional strength . . . (Kevles, 1986:8,9).
One reason nineteenth century biologists argued for women's inferiority was because Darwin believed that "unchecked female militancy threatened to produce a perturbance of the races" and to "divert the orderly process of evolution" (Fee, 1979:415).
Darwin taught that human sex differences were due partly to sexual selection, specifically because men must prove themselves physically and intellectually superior to other men in the competition for women, whereas women must be superior primarily in sexual attraction. Darwin used examples of cultures that require the men to fight competitors to retain their wives to support this conclusion. Because "the strongest party always carries off the prize," the result is that "a weak man, unless he be a good hunter . . . is seldom permitted to keep a wife that a stronger man thinks worth his notice" (1896:562).
Other examples Darwin uses to illustrate his conclusion that evolutionary forces caused men to be superior to women included animal comparisons. Since humans evolved from animals, and "no one disputes that the bull differs in disposition from the cow, the wild-boar from the sow, the stallion from the mare, and, as is well known through the keepers of menageries, the males of the larger apes from the females," the same must be true with human females (Darwin, 1896:563). Further, some of the traits of women "are characteristic of the lower races, and anti therefore of a past and lower state of civilization" (1896:563,564). In summary, Darwin concludes that men attain,
. . . a higher eminence, in whatever he takes up, than can women&mdashwhether requiring deep thought, reason, or imagination, or merely the use of the senses and hands. If two lists were made of the most eminent men and women in poetry, painting, sculpture, music (inclusive of both composition and performance), history, science, and philosophy, with half-a-dozen names under each subject, the two lists would not bear comparison. We may also infer, from the law of the deviation from averages, so well illustrated by Mr. Galton, in his work on "Hereditary Genius" that . . . the average of mental power in man must be above that of women (Darwin, 1896:564).
Obviously, Darwin totally ignored the influence of culture, the environment, social roles, and the relatively few opportunities that existed in his day, as well as historically, for both men and women.
The conclusion that women are evolutionarily inferior to men is at the core of Darwin's major contribution to evolutionary theory: natural anti-sexual selection. Since selection in the long term prunes out the weak, all factors which facilitate saving the weak work against evolution. Males are subjected to more selection pressures than women, including the supposed tack that, in earlier times, the stronger, quicker, and more intelligent males were more apt to survive a hunt and bring back food. Consequently, natural selection would evolve males to a greater degree than females. Since women historically have focused primarily on domestic, often menial, repetitive tasks and not on hunting, they were less affected by selection pressures. Further, the long tradition of males has been to protect women: only men went to battle, and the common war norms forbade deliberately killing women. War pruned the weaker men, and only the best survived to return home and reproduce. The eminent evolutionist, Topinard, concluded that men were superior because they fought to protect both themselves and their wives and their families. Further, Topinard taught that males have
all of the responsibility and the cares of tomorrow [and are] . . . constantly active in combating the environment and human rivals, and thus need] . . . more brains than the woman whom he must protect and nourish . . . the sedentary women, lacking any interior occupations, whose role is to raise children, love, and be passive (quoted in Gould, 1981:104).
Women's inferiority&mdasha fact taken for granted by most scientists in the 1800s&mdashwas a major proof of evolution by natural selection. Gould claims that there were actually "few egalitarian scientists" at this time. Almost all believed that "Negroes and women" were intellectually inferior. These scientists were not repeating prejudices without extensive work and thought they were attempting to verify this major plank in evolutionary theory by trying to prove, scientifically, that women were inferior.
One approach which was seized upon to substantiate that females were generally inferior to males was to prove that their brain capacity was smaller. Researchers first endeavored to demonstrate empirically that female cranial capacity was smaller, and then that brain capacity was related to intelligence, a more difficult task (Van Valen, 1974:417-423).
Among the numerous researchers that used craniology to "prove" the intellectual inferiority of women, one of the most eminent was Paul Broca (1824-1880). One of Europe's "most prestigious anthropologists" and a leader in the development of physical anthropology as a science, Broca, in 1859, founded the prestigious Anthropological Society (Fee, 1979:415). A major preoccupation of the society then was measuring various human traits, including skulls to "delineate human groups and assess their relative worth" (Gould, 1981:83). Broca's conclusion was that human brains are:
. . . larger in mature adults than in the elderly, in men than in women, in eminent men than in men of mediocre talent, in superior races than in inferior races . . . other things equal, there is a remarkable relationship between the development of intelligence and the volume of the brain (Gould, 1981, p. 83).
And, as Gould notes, Broca's research was not superficial: "One cannot read Broca without gaining enormous respect for his care in generating data" (1981:85).
Broca was especially concerned about proving women's inferiority to men: "Of all his comparisons between groups, Broca collected most information on the brains of women vs. men . . ." (Gould, 1981:103). He concluded that ''the relatively small size of the female brain depends in part upon her physical inferiority and in part upon her intellectual inferiority" (Gould, 1981:104). Broca also concluded that the disparity between men's and women's brains was still becoming even greater, which he explained was the "result of differing evolutionary pressures upon dominant men and passive women" (Gould, 1981:104).
These views were expounded by many of the most prominent evolutionists of Darwin's day. The thunder of the field of social psychology and a pioneer in the collective behavior field was Gustave Le Bon (1841-1931). This scientist, whose classic study of crowd behavior (The Crowd 1895) is familiar to every social science student, wrote that even in:
. . . the most intelligent races . . . are a large number of women whose brains are closer in size to those of gorillas than to the most developed male brains. This inferiority is so obvious that no one can contest it for a moment only its degree is worth discussion. . . . Women . . . represent the most inferior forms of human evolution and . . . are closer to children and savages than to an adult, civilized man. They excel in fickleness, inconsistency, absence of thought and logic, and incapacity to reason. Without a doubt there exist some distinguished women, very superior to the average man but they are as exceptional as the birth of any monstrosity, as, for example, of a gorilla with two heads consequently, we may neglect them entirely (Gould, 1981:104,105).
Re-evaluation of the conclusion that females were less intelligent found major flaws both in the evidence that "proved" women's inferiority and in major aspects of evolution theory.
Fisher even argues that the whole theory of natural selection is questionable, quoting Chomsky's words that:
. . . the processes by which the human mind achieved its present state of complexity . . . are a total mystery. . . . It is perfectly safe to attribute this development to "natural selection," so long as we realize that there is no substance to this assertion, that it amounts to nothing more than a belief that there is some naturalistic explanation for these phenomena (1972:97).
Another method used to attack the female-inferiority conclusion of evolution was to attack the evidence of evolutionary theory itself. Fisher, for example, makes the following observation:
The difficulties of postulating theories about human origins on the actual brain organization of our presumed fossil ancestors, with only a few limestone impregnated skulls&mdashmost of them bashed, shattered, and otherwise altered by the passage of millions of years&mdashas evidence, would seem to be astronomical (1979:113).
Actually, many of the attempts to disprove the evolutionary view that women are intellectually inferior to men attacked the core of evolutionary theory because it is inexorably bound with human-group inferiority, which must exist, from which natural selection may select. The inferiority-of-women conclusion was so ingrained in biology, Morgan concludes, that thinkers in this area tended to "sheer away from the sole subject of biology and origins," hoping they could ignore it and "concentrate on ensuring that in the future things will be different" (Morgan, 1972:2). She stresses that we cannot ignore evolutionary biology, though, because believing the "jungle heritage and the evolution of man as a hunting carnivore has taken root in man's mind as firmly as Genesis ever did." She concludes that evolution must be reevaluated, and that scientists have "sometimes gone astray" because of prejudice and philosophical prescriptions. She argues that the prominent evolutionary view that women are biologically inferior to men must be challenged, and in this and scores of other works that preceded her, dozens of writers have adroitly overturned the conclusion that women are biologically inferior to men, and, by so doing, have undermined a major plank in evolutionism.
Chomsky, Noam. 1972. Language and Mind. New York: Harcourt, Brace, and World.
Darwin, Charles. 1896. The Descent of Man and Selection in Relation to Sex. New York: D. Appleton and Company.
-----. (Nora Barlow, Ed.). 1958. The Autobiography of Charles Darwin, 1809-1882. New York: W. W. Norton & Co., Inc.
Dyer, Gwynne. 1985. War. New York: Crown Publishers, Inc.
Fee, Elizabeth. 1979. "Nineteenth-Century Craniology: The Study of the Female Skull." Bulletin of the History of Medicine, 53:415-433.
Fisher, Elizabeth. 1979. Woman's Creation: Sexual Evolution and the Shaping of Society. Garden City, NY: Anchor Press/Doubleday.
Gould, Stephen Jay. 1981. The Mismeasure of Man. New York: W. W. Norton & Company.
Kevics, Beltyann. 1986. Females of the Species: Sex and Survival in the Animal Kingdom. Cambridge, MA: Harvard University Press.
Morgan, Elaine. 1972. The Descent of Woman. New York: Stein and Day.
Van Valen, Leigh. 1974. "Brain Size and Intelligence in Man." American Journal of Physical Anthropology, 40:417 423.
* Dr. Bergman is on the science faculty at Northwest State College, Ohio.
Cite this article: Bergman, J. 1994. Darwin's Teaching of Women's Inferiority. Acts & Facts. 23 (3).
Austin CR, Bishop MWH, 1959. Presence of spermatozoa in the uterine-tube mucosa of bats. J Endocrinol 18: R7-R8.
Bartley MM, 1992. Darwin and domestication: studies on inheritance. J Hist Biol 25: 307–333.
Bateson W, 1906. The progress of genetic research. In: Scientific papers of William Bateson (edited by Punnett, R. C.), 1928, 2: 142–151.
Bateson W, 1910. Heredity and variation in modern lights. In: Darwin and modern science. Cambridge University Press: 84–101.
Beardmore JA, Lints FA, Al-Baldawi ALF, 1975. Parental age and heritability of sternopleural chaeta number inDrosophila melanogaster. Heredity 34: 71–82.
Belyaev DK, Ruvinsky AO, Borodin PM, 1981. Inheritance of alternative states of the fused gene in mice. J Hered 72: 107–112.
Bulant C, Gallais A, 1998. Xenia effects in maize with normal endosperm: I. Importance and stability. Crop Sci 38: 1517–1525.
Bunting J, 1974. Charles Darwin. Bailey Brothers & Swinfen LTD: 114.
Burbank L, 1927. The harvest of the years. Boston & New York: Hoghton Mifflin Company.
Cox CF, 1909. Charles Darwin and the mutation theory. Am Nat 43: 65–91.
Darwin C, 1872. On the origin of species by means of natural selection or the preservation of favoured races in the struggle for life, 6th ed. London: John Murray.
Darwin C, 1868. The variation of animals and plants under domestication. London: John Murray.
Darwin C, 1987. Charles Darwin’s notebook, 1836–1844. New York: Cornell University Press.
Davenport CB, 1933. An alleged case of inheritance of acquired characters. Am Nat 67: 549–558.
Denney JO, 1992. Xenia includes metaxenia. Hort Science 27: 722–728.
de Vries, 1910. Intracellular Pangenesis. Chicago: The Open Court Publishing Co. (translated from the German by C. Stuart Gager): 7.
de Vries, 1911. The mutation theory. London: Kegan
Paul and Co. Duc G, Moessner A, Moussy F, Mousset-Declas C, 2001. A xenia effect on number and volume of cotyledon cells and on seed weight in faba bean (Vicia faba L.) Euphytica 117: 169–174.
Dunn LC, 1973. Xenia and the origin of genetics. Proc Am Philos Soc 117: 105–111.
Endersby J, 2003. Darwin on generation, pangenesis and sexual selection. In: Hodge J, Radick G, eds. The Cambridge companion to Darwin. Cambridge University Press, 69–91.
Engel ML, Chaboud A, Dumas C, MCormick S, 2003. Sperm cells ofZea mays have a complex complement of mRNAs. Plant J 34: 697–707.
Frankel R, 1956. Graft-induced transmission to progeny of cytoplasmic male sterility inPetunia. Science 124: 684–685.
Galton F, 1871. Experiments in Pangenesis, by breeding from rabbits of a pure variety, into whose circulation blood taken from other varieties had previously been largely transfused. Proc R Soc Lond 19: 393–410.
Ghiselin MT, 1975. The rationale of Pangenesis, Genetics 79: 47–57.
Gorcynski RM, Kennedy M, Macrae S, Ciampi A, 1983. A possible maternal effect in the abnormal hyporesponsiveness to specific alloantigens in offspring born to neonatally tolerant fathers. J Immunol 131: 1115–1120.
Hall BK, 1995. Atavisms and atavistic mutations. Nat Genet 10: 126–127.
Hammond J, 1958. Darwin and animal breeding. In: Barnet A, ed. A Century of Darwin. London: Heinemann: 85–101.
Hui L, 1989. Why does my newborn daughter resemble my former husband?Family (9): 1.
Landman OE, 1991. The inheritance of acquired characteristics. Annu Rev Genet 25: 1–20.
Liu YS, 2005. Reversion: going back to Darwin’s works. Trends Plant Sci 10: 459–460.
Liu YS, 2006. The historical and modern genetics of plant graft hybridization. Adv Genet 56: 101–129.
Liu YS, 2007. Like father like son: a fresh review of the inheritance of acquired characters. EMBO Rep 8: 798–803.
Liu YS, 2008a. A new perspective on Darwin’s Pangenesis. Biol Rev Camb Philos Soc 83: 141–149.
Liu YS, 2008b. A novel mechanism for xenia?HortScience 43: 706.
Lizana GB, Prado JAS, 1994. Effects of parents’ age on the level of polymorphism at the Adh locus inDrosophila melanogaster: I. Effects on the genic and genotypic segregation of the offspring. J Hered 85: 327–331.
Lolle SJ, Victor JL, Young JM, Pruitt RE, 2005. Genome-wide non-Mendelian inheritance of extra-genomic in formation inArabidopsis. Nature 434: 505–509.
Lucas WJ, Yoo B-C, Kragler F, 2001. RNA as a long-distance information macromolecule in plants. Nat Rev Mol Cell Biol 2: 849–857.
Mayr E, 1991. One long argument: Charles Darwin and the genesis of modern evolutionary thought. Cambridge (Mass.): Harvard University Press.
Mei D, 2000. The son who resembles his mother’s former husband. Healthy Life 11: 37.
Michurin IV, 1949. Selected Works. Moscow: Foreign Languages Publishing House.
Mole, 2006. How we know I: strange dreams. J Cell Sci 119: 1–2.
Moore JA, 1963. Heredity and development. New York: Oxford University Press: 1–14.
Muntzing A, 1959. Darwin’s views on variation under domestication in the light of present-day knowledge. Proc Am Philos Soc 103: 190–220.
Ohta Y, 1991. Graft-transformation, the mechanism for graft-induced genetic changes in higher plants. Euphytica 55: 91–99.
Pahlavani, MH, Abolhasani K, 2006. Xenia effect on seed and embryo size in cotton. J Appl Genet 47: 331–335.
Sopikov PM, 1954. Changes in heredity by the parenteral administration of blood. Agrobiologiia 6: 34–45.
Steele EJ, Lindley RA, Blanden RV, 1998. Lamarck’s signature: how retrogenes are changing Darwin’s natural selection paradigm. Massachusetts: Perseus Books.
Stegemann S, Bock R, 2009. Exchange of genetic material between cells in plant tissue grafts. Science 324: 649–651.
Stroun M, Anker P, 2005. Circulating DNA in higher organisms cancer detection brings back to life an ignored phenomenon. Cell Mol Biol 51: 767–774.
Sturtevant AH, 1965. A history of genetics. New York: Harper & Row.
Taller J, Yagishita N, Hirata Y, 1999. Graft-induced variants as a source of novel characteristics in the breeding of pepper (Capsicum annuum L.). Euphytica 108: 73–78.
Tchang TR, Shi XB, Pang YB, 1964. An induced monster ciliate transmitted through three hundred and more generations. Sci Sin 13: 850–853.
Wallace HM, Lee LS, 1999. Pollen source, fruit set and xenia in mandarins. J Hortic Sci Biotechnol 74: 82–86.
Weismann A, 1904. The evolution theory. London: Edward Arnold.
Winther RG, 2000. Darwin on variation and heredity. J Hist Biol 33: 425–455.
For an introduction to various aspects of the topic, see
the relevant portions of the following works, which have
rich bibliographical leads to other studies and to the sources.
W. R. Coleman, “Cell, Nucleus, and Inheritance: An His-
torical Study,” Proceedings of the American Philosophical
Society, 109 (1965), 124-58. L. C. Dunn, A Short History
of Genetics (New York, 1965). A. E. Gaisinovich, “U istokov
sovetskoi genetiki: bor'ba s lamarkizmom (1922-27),”
Genetika, 4, No. 6 (1968), 158-75. Verne Grant, The Origin
of Adaptations (New York, 1963). D. Joravsky, Soviet
Marxism and Natural Science, 1917-32 (New York, 1961)
idem, The Lysenko Affair (Cambridge, Mass., 1970). V. L.
Komarov, Lamark (Moscow, 1925), in idem, Izbrannye
sochineniia, 1 (1945) idem, “Lamark i ego nauchnoe
znachenie,” in Lamarck, Filosofia zoologii (Moscow, 1935),
1, xi-xcvii. Zh. A. Medvedev, The Rise and Fall of T. D.
Lysenko (New York, 1969). R. C. Olby, Origins of Mendelism
(London, 1966). Jean Rostand, L'atomisme en biologie (Paris,
1956). Hans Stubbe, Kurze Geschichte der Genetik (Jena,
1965). C. Zirkle, “Early History of the Idea of the Inherit-
ance of Acquired Characters and of Pangenesis,” Transac-
tions of the American Philosophical Society, 335 (1946),
Other works cited in this article include the following.
C. D. Darlington, “Purpose and Particles in the Study of
Heredity,” in E. A. Underwood, ed., Science, Medicine, and
History: Essays on the Evolution of Scientific Thought
(London, 1953), II, 472-81. Th. Dobzhansky, Mankind
Evolving (New Haven, 1962). Marvin Harris, The Rise of
Anthropological Theory (New York, 1968). T. D. Lysenko,
Agrobiologiia, 6th ed. (Moscow, 1952 English trans., 1954),
the largest collection of his works. Robert Mackintosh, From
Comte to Benjamin Kidd: The Appeal to Biology or Evolution
for Human Guidance (New York, 1899). I. V. Michurin,
Sochineniia, 4 vols. (Moscow, 1939-41 2nd ed., 1948).
B. A. Vakar, Vazhneishie khlebnye zlaki (Novosibirsk, 1929).
[See also Biological Conceptions in Antiquity Evolutionism
Genetic Continuity Inheritance through Pangenesis Per-
Darwin's Influence on Modern Thought
Great minds shape the thinking of successive historical periods. Luther and Calvin inspired the Reformation Locke, Leibniz, Voltaire and Rousseau, the Enlightenment. Modern thought is most dependent on the influence of Charles Darwin
Editor's Note: This story, originally published in the July 2000 issue of Scientific American, is being made available due to the 150th anniversary of Charles Darwin's On the Origin of the Species
Clearly, our conception of the world and our place in it is, at the beginning of the 21st century, drastically different from the zeitgeist at the beginning of the 19th century. But no consensus exists as to the source of this revolutionary change. Karl Marx is often mentioned Sigmund Freud has been in and out of favor Albert Einstein&rsquos biographer Abraham Pais made the exuberant claim that Einstein&rsquos theories &ldquohave profoundly changed the way modern men and women think about the phenomena of inanimate nature.&rdquo No sooner had Pais said this, though, than he recognized the exaggeration. &ldquoIt would actually be better to say &lsquomodern scientists&rsquo than &lsquomodern men and women,&rsquo&rdquo he wrote, because one needs schooling in the physicist&rsquos style of thought and mathematical techniques to appreciate Einstein&rsquos contributions in their fullness. Indeed, this limitation is true for all the extraordinary theories of modern physics, which have had little impact on the way the average person apprehends the world.
The situation differs dramatically with regard to concepts in biology. Many biological ideas proposed during the past 150 years stood in stark conflict with what everybody assumed to be true. The acceptance of these ideas required an ideological revolution. And no biologist has been responsible for more&mdashand for more drastic&mdashmodifications of the average person&rsquos worldview than Charles Darwin.
Darwin&rsquos accomplishments were so many and so diverse that it is useful to distinguish three fields to which he made major contributions: evolutionary biology the philosophy of science and the modern zeitgeist. Although I will be focusing on this last domain, for the sake of completeness I will put forth a short overview of his contributions&mdashparticularly as they inform his later ideas&mdashto the first two areas.
A Secular View of Life
Darwin founded a new branch of life science, evolutionary biology. Four of his contributions to evolutionary biology are especially important, as they held considerable sway beyond that discipline. The first is the nonconstancy of species, or the modern conception of evolution itself. The second is the notion of branching evolution, implying the common descent of all species of living things on earth from a single unique origin. Up until 1859, all evolutionary proposals, such as that of naturalist Jean- Baptiste Lamarck, instead endorsed linear evolution, a teleological march toward greater perfection that had been in vogue since Aristotle&rsquos concept of Scala Naturae, the chain of being. Darwin further noted that evolution must be gradual, with no major breaks or discontinuities. Finally, he reasoned that the mechanism of evolution was natural selection.
These four insights served as the foundation for Darwin&rsquos founding of a new branch of the philosophy of science, a philosophy of biology. Despite the passing of a century before this new branch of philosophy fully developed, its eventual form is based on Darwinian concepts. For example, Darwin introduced historicity into science. Evolutionary biology, in contrast with physics and chemistry, is a historical science&mdashthe evolutionist attempts to explain events and processes that have already taken place. Laws and experiments are inappropriate techniques for the explication of such events and processes. Instead one constructs a historical narrative, consisting of a tentative reconstruction of the particular scenario that led to the events one is trying to explain.
For example, three different scenarios have been proposed for the sudden extinction of the dinosaurs at the end of the Cretaceous: a devastating epidemic a catastrophic change of climate and the impact of an asteroid, known as the Alvarez theory. The first two narratives were ultimately refuted by evidence incompatible with them. All the known facts, however, fit the Alvarez theory, which is now widely accepted. The testing of historical narratives implies that the wide gap between science and the humanities that so troubled physicist C. P. Snow is actually nonexistent&mdashby virtue of its methodology and its acceptance of the time factor that makes change possible, evolutionary biology serves as a bridge.
The discovery of natural selection, by Darwin and Alfred Russel Wallace, must itself be counted as an extraordinary philosophical advance. The principle remained unknown throughout the more than 2,000-year history of philosophy ranging from the Greeks to Hume, Kant and the Victorian era. The concept of natural selection had remarkable power for explaining directional and adaptive changes. Its nature is simplicity itself. It is not a force like the forces described in the laws of physics its mechanism is simply the elimination of inferior individuals. This process of nonrandom elimination impelled Darwin&rsquos contemporary, philosopher Herbert Spencer, to describe evolution with the now familiar term &ldquosurvival of the fittest.&rdquo (This description was long ridiculed as circular reasoning: &ldquoWho are the fittest? Those who survive.&rdquo In reality, a careful analysis can usually determine why certain individuals fail to thrive in a given set of conditions.)
The truly outstanding achievement of the principle of natural selection is that it makes unnecessary the invocation of &ldquofinal causes&rdquo&mdashthat is, any teleological forces leading to a particular end. In fact, nothing is predetermined. Furthermore, the objective of selection even may change from one generation to the next, as environmental circumstances vary.
A diverse population is a necessity for the proper working of natural selection. (Darwin&rsquos success meant that typologists, for whom all members of a class are essentially identical, were left with an untenable viewpoint.) Because of the importance of variation, natural selection should be considered a two-step process: the production of abundant variation is followed by the elimination of inferior individuals. This latter step is directional. By adopting natural selection, Darwin settled the several-thousandyear- old argument among philosophers over chance or necessity. Change on the earth is the result of both, the first step being dominated by randomness, the second by necessity.
Darwin was a holist: for him the object, or target, of selection was primarily the individual as a whole. The geneticists, almost from 1900 on, in a rather reductionist spirit preferred to consider the gene the target of evolution. In the past 25 years, however, they have largely returned to the Darwinian view that the individual is the principal target.
For 80 years after 1859, bitter controversy raged as to which of four competing evolutionary theories was valid. &ldquoTransmutation&rdquo was the establishment of a new species or new type through a single mutation, or saltation. &ldquoOrthogenesis&rdquo held that intrinsic teleological tendencies led to transformation. Lamarckian evolution relied on the inheritance of acquired characteristics. And now there was Darwin&rsquos variational evolution, through natural selection. Darwin&rsquos theory clearly emerged as the victor during the evolutionary synthesis of the 1940s, when the new discoveries in genetics were married with taxonomic observations concerning systematics, the classification of organisms by their relationships. Darwinism is now almost unanimously accepted by knowledgeable evolutionists. In addition, it has become the basic component of the new philosophy of biology.
A most important principle of the new biological philosophy, undiscovered for almost a century after the publication of On the Origin of Species, is the dual nature of biological processes. These activities are governed both by the universal laws of physics and chemistry and by a genetic program, itself the result of natural selection, which has molded the genotype for millions of generations. The causal factor of the possession of a genetic program is unique to living organisms, and it is totally absent in the inanimate world. Because of the backward state of molecular and genetic knowledge in his time, Darwin was unaware of this vital factor.
Another aspect of the new philosophy of biology concerns the role of laws. Laws give way to concepts in Darwinism. In the physical sciences, as a rule, theories are based on laws for example, the laws of motion led to the theory of gravitation. In evolutionary biology, however, theories are largely based on concepts such as competition, female choice, selection, succession and dominance. These biological concepts, and the theories based on them, cannot be reduced to the laws and theories of the physical sciences. Darwin himself never stated this idea plainly. My assertion of Darwin&rsquos importance to modern thought is the result of an analysis of Darwinian theory over the past century. During this period, a pronounced change in the methodology of biology took place. This transformation was not caused exclusively by Darwin, but it was greatly strengthened by developments in evolutionary biology. Observation, comparison and classification, as well as the testing of competing historical narratives, became the methods of evolutionary biology, outweighing experimentation.
I do not claim that Darwin was single-handedly responsible for all the intellectual developments in this period. Much of it, like the refutation of French mathematician and physicist Pierre-Simon Laplace&rsquos determinism, was &ldquoin the air.&rdquo But Darwin in most cases either had priority or promoted the new views most vigorously.
The Darwinian Zeitgeist
A 21st-century person looks at the world quite differently than a citizen of the Victorian era did. This shift had multiple sources, particularly the incredible advances in technology. But what is not at all appreciated is the great extent to which this shift in thinking indeed resulted from Darwin&rsquos ideas.
Remember that in 1850 virtually all leading scientists and philosophers were Christian men. The world they inhabited had been created by God, and as the natural theologians claimed, He had instituted wise laws that brought about the perfect adaptation of all organisms to one another and to their environment. At the same time, the architects of the scientific revolution had constructed a worldview based on physicalism (a reduction to spatiotemporal things or events or their properties), teleology, determinism and other basic principles. Such was the thinking of Western man prior to the 1859 publication of On the Origin of Species. The basic principles proposed by Darwin would stand in total conflict with these prevailing ideas.
First, Darwinism rejects all supernatural phenomena and causations. The theory of evolution by natural selection explains the adaptedness and diversity of the world solely materialistically. It no longer requires God as creator or designer (although one is certainly still free to believe in God even if one accepts evolution). Darwin pointed out that creation, as described in the Bible and the origin accounts of other cultures, was contradicted by almost any aspect of the natural world. Every aspect of the &ldquowonderful design&rdquo so admired by the natural theologians could be explained by natural selection. (A closer look also reveals that design is often not so wonderful&mdashsee &ldquoEvolution and the Origins of Disease,&rdquo by Randolph M. Nesse and George C. Williams Scientific American, November 1998.) Eliminating God from science made room for strictly scientific explanations of all natural phenomena it gave rise to positivism it produced a powerful intellectual and spiritual revolution, the effects of which have lasted to this day.
Second, Darwinism refutes typology. From the time of the Pythagoreans and Plato, the general concept of the diversity of the world emphasized its invariance and stability. This viewpoint is called typology, or essentialism. The seeming variety, it was said, consisted of a limited number of natural kinds (essences or types), each one forming a class. The members of each class were thought to be identical, constant, and sharply separated from the members of other essences.
Variation, in contrast, is nonessential and accidental. A triangle illustrates essentialism: all triangles have the same fundamental characteristics and are sharply delimited against quadrangles or any other geometric figures. An intermediate between a triangle and a quadrangle is inconceivable. Typological thinking, therefore, is unable to accommodate variation and gives rise to a misleading conception of human races. For the typologist, Caucasians, Africans, Asians or Inuits are types that conspicuously differ from other human ethnic groups. This mode of thinking leads to racism. (Although the ignorant misapplication of evolutionary theory known as &ldquosocial Darwinism&rdquo often gets blamed for justifications of racism, adherence to the disproved essentialism preceding Darwin in fact can lead to a racist viewpoint.)
Darwin completely rejected typological thinking and introduced instead the entirely different concept now called population thinking. All groupings of living organisms, including humanity, are populations that consist of uniquely different individuals. No two of the six billion humans are the same. Populations vary not by their essences but only by mean statistical differences. By rejecting the constancy of populations, Darwin helped to introduce history into scientific thinking and to promote a distinctly new approach to explanatory interpretation in science.
Third, Darwin&rsquos theory of natural selection made any invocation of teleology unnecessary. From the Greeks onward, there existed a universal belief in the existence of a teleological force in the world that led to ever greater perfection. This &ldquofinal cause&rdquo was one of the causes specified by Aristotle. After Kant, in the Critique of Judgment, had unsuccessfully attempted to describe biological phenomena with the help of a physicalist Newtonian explanation, he then invoked teleological forces. Even after 1859, teleological explanations (orthogenesis) continued to be quite popular in evolutionary biology. The acceptance of the Scala Naturae and the explanations of natural theology were other manifestations of the popularity of teleology. Darwinism swept such considerations away.
(The designation &ldquoteleological&rdquo actually applied to various different phenomena. Many seemingly end-directed processes in inorganic nature are the simple consequence of natural laws&mdasha stone falls or a heated piece of metal cools because of laws of physics, not some end-directed process. Processes in living organisms owe their apparent goal-directedness to the operation of an inborn genetic or acquired program. Adapted systems, such as the heart or kidneys, may engage in activities that can be considered goal seeking, but the systems themselves were acquired during evolution and are continuously fine-tuned by natural selection. Finally, there was a belief in cosmic teleology, with a purpose and predetermined goal ascribed to everything in nature. Modern science, however, is unable to substantiate the existence of any such cosmic teleology.)
Fourth, Darwin does away with determinism. Laplace notoriously boasted that a complete knowledge of the current world and all its processes would enable him to predict the future to infinity. Darwin, by comparison, accepted the universality of randomness and chance throughout the process of natural selection. (Astronomer and philosopher John Herschel referred to natural selection contemptuously as &ldquothe law of the higgledy-piggledy.&rdquo) That chance should play an important role in natural processes has been an unpalatable thought for many physicists. Einstein expressed this distaste in his statement, &ldquoGod does not play dice.&rdquo Of course, as previously mentioned, only the first step in natural selection, the production of variation, is a matter of chance. The character of the second step, the actual selection, is to be directional.
Despite the initial resistance by physicists and philosophers, the role of contingency and chance in natural processes is now almost universally acknowledged. Many biologists and philosophers deny the existence of universal laws in biology and suggest that all regularities be stated in probabilistic terms, as nearly all so-called biological laws have exceptions. Philosopher of science Karl Popper&rsquos famous test of falsification therefore cannot be applied in these cases.
Fifth, Darwin developed a new view of humanity and, in turn, a new anthropocentrism. Of all of Darwin&rsquos proposals, the one his contemporaries found most difficult to accept was that the theory of common descent applied to Man. For theologians and philosophers alike, Man was a creature above and apart from other living beings. Aristotle, Descartes and Kant agreed on this sentiment, no matter how else their thinking diverged. But biologists Thomas Huxley and Ernst Haeckel revealed through rigorous comparative anatomical study that humans and living apes clearly had common ancestry, an assessment that has never again been seriously questioned in science. The application of the theory of common descent to Man deprived man of his former unique position.
Ironically, though, these events did not lead to an end to anthropocentrism. The study of man showed that, in spite of his descent, he is indeed unique among all organisms. Human intelligence is unmatched by that of any other creature. Humans are the only animals with true language, including grammar and syntax. Only humanity, as Darwin emphasized, has developed genuine ethical systems. In addition, through high intelligence, language and long parental care, humans are the only creatures to have created a rich culture. And by these means, humanity has attained, for better or worse, an unprecedented dominance over the entire globe.
Sixth, Darwin provided a scientific foundation for ethics. The question is frequently raised&mdashand usually rebuffed&mdash as to whether evolution adequately explains healthy human ethics. Many wonder how, if selection rewards the individual only for behavior that enhances his own survival and reproductive success, such pure selfishness can lead to any sound ethics. The widespread thesis of social Darwinism, promoted at the end of the 19th century by Spencer, was that evolutionary explanations were at odds with the development of ethics.
We now know, however, that in a social species not only the individual must be considered&mdashan entire social group can be the target of selection. Darwin applied this reasoning to the human species in 1871 in The Descent of Man. The survival and prosperity of a social group depends to a large extent on the harmonious cooperation of the members of the group, and this behavior must be based on altruism. Such altruism, by furthering the survival and prosperity of the group, also indirectly benefits the fitness of the group&rsquos individuals. The result amounts to selection favoring altruistic behavior.
Kin selection and reciprocal helpfulness in particular will be greatly favored in a social group. Such selection for altruism has been demonstrated in recent years to be widespread among many other social animals. One can then perhaps encapsulate the relation between ethics and evolution by saying that a propensity for altruism and harmonious cooperation in social groups is favored by natural selection. The old thesis of social Darwinism&mdashstrict selfishness&mdashwas based on an incomplete understanding of animals, particularly social species.
The Influence of New Concepts
Let me now try to summarize my major findings. No educated person any longer questions the validity of the so-called theory of evolution, which we now know to be a simple fact. Likewise, most of Darwin&rsquos particular theses have been fully confirmed, such as that of common descent, the gradualism of evolution, and his explanatory theory of natural selection.
I hope I have successfully illustrated the wide reach of Darwin&rsquos ideas. Yes, he established a philosophy of biology by introducing the time factor, by demonstrating the importance of chance and contingency, and by showing that theories in evolutionary biology are based on concepts rather than laws. But furthermore&mdashand this is perhaps Darwin&rsquos greatest contribution&mdashhe developed a set of new principles that influence the thinking of every person: the living world, through evolution, can be explained without recourse to supernaturalism essentialism or typology is invalid, and we must adopt population thinking, in which all individuals are unique (vital for education and the refutation of racism) natural selection, applied to social groups, is indeed sufficient to account for the origin and maintenance of altruistic ethical systems cosmic teleology, an intrinsic process leading life automatically to ever greater perfection, is fallacious, with all seemingly teleological phenomena explicable by purely material processes and determinism is thus repudiated, which places our fate squarely in our own evolved hands.
To borrow Darwin&rsquos phrase, there is grandeur in this view of life. New modes of thinking have been, and are being, evolved. Almost every component in modern man&rsquos belief system is somehow affected by Darwinian principles.
This article is based on the September 23, 1999, lecture that Mayr delivered in Stockholm on receiving the Crafoord Prize from the Royal Swedish Academy of Science.
Pangenesis & the Problems It Solved
One of the hallmarks of a productive scientific idea is the range of phenomena for which it accounts. By this measure, pangenesis must have seemed like an extraordinarily productive notion and one that its founder was likely to accept as accurate. With this one idea it was possible to explain a huge number of related puzzles presented by the natural world. For instance, by assuming that gemmules could lie dormant for generations, "reversion" (the sudden reappearance of old traits) is easily explained. Gemmules provided by a male might remain in circulation in his mare and cause a permanent change in the inheritance pattern as in the assumed case with the horse and quagga. Even regeneration could be explained neatly by pangenesis. Perhaps a severed limb, before its removal, sent out into the body gemmules that "remembered" the proper limb structure and later regrouped to direct its reconstruction.
Pangenesis could prevent swamping because gemmules might reproduce themselves after being released from an organ, making it possible for a few changed gemmules to "become sufficiently numerous to overpower and supplant the old [existing] gemmules" (Darwin, 1868b, p. 395). This realization must have given Darwin a great degree of satisfaction because it would permit him to respond to the important criticism of Fleeming Jenkin, who suggested that the swamping would make natural selection impossible by removing rare but useful traits from the population. Darwin charitably gave Jenkin some credit for the development of pangenesis by saying "Fleeming Jenkin has given me much trouble, but has been of more real use to me than any other essay or review" (cited in Browne, 2002, p. 282).
Finally, and most importantly, pangenesis would explain the source of new variation through use and disuse. Even if it is not an accurate argument, as any biology student would suggest, pangenesis does explain how inheritance works (all before the discovery of Mendel's laws, the gene, and DNA). Such explanatory strength should have firmly convinced Darwin of the validity of pangenesis but, as we will see, he spent considerable time convincing others even as he continued to persuade himself.
In the latter half of the twentieth century, the view of the process by which new species originated was based on meshing Darwinian variation and selection with work on population genetics and mutation. This view, the evolutionary synthesis, suggested that mutation within individuals led to genetic variation within a population should a subgroup of that population become genetically isolated in a novel environment, a mix of unbalanced variation and new mutation within the subgroup would lead to new phenotypes appearing. In due course, one of these might reproduce better than the original phenotype so that it would take over and eventually lead to the appearance of a new species with a novel genotype .
The enormous amount of molecular information that has emerged during the last couple of decades is making us review this synthesis, partly because we now know that the relationship between the phenotype and genotype is not as simple as previously assumed, partly because the genome is a richer, more complicated world than the scientists who put together the modern synthesis could ever have supposed and partly because there is data that does not fit comfortably within the synthesis. The two interesting and important books under review here set out to examine aspects of the state of evolutionary science now, the one taking an unashamedly contemporary position, the other starting from 200 years ago. Before discussing what they have to say, it is worth taking a look at their context by considering the state of evolutionary biology today.
The evidence for evolution itself is robust as it comes from the three independent lines that each tells the same story: history (fossil record and isotope dating), morphology (taxonomic relationship and comparative embryology in living organisms - evolutionary change starts off as developmental change) and molecular sequence relationships. While the evolutionary synthesis is of course compatible with evolution, the evidence to support it is actually much thinner than is generally supposed this is mainly because data is hard to come by in processes that are intrinsically slow and rare. One line of supporting evidence is the existence of ring species such as the various greenish warblers around the Himalayas where neighbouring subspecies around the ring can interbreed, but there is a break point where the two adjacent ones, although members of the same family, cannot and so have to be viewed as separate species . A line of work that the evolutionary synthesis cannot explain so easily is Waddington's remarkable set of experiments on selection . The most famous of these involved first making a phenocopy of the bithorax mutation (a four-winged fly instead of one with two wings and two halteres) by ether treatment of wild-type flies and then interbreeding these phenocopies under strong selection (rejecting all offspring that didn't produce the ether phenocopy). He found that, after
20 generations of interbreeding and selection, he had a population where the four-winged flies bred true without further ether treatment. Waddington called this process, which was too fast to be initiated by novel mutations, genetic assimilation.
There is a serious underlying problem with the evolutionary synthesis: it is based on a minimalist Mendelian view of genetics which assumes that a very small number of genes underpin a trait and a mutant gene leads to an abnormal phenotype. While the advantage of the formulation is that it provides a model for evolutionary genetics , the disadvantage is that the approach assumes a naively simplistic view of how genes generate traits, as Waddington pointed out in the '50s . If more than about three genes (nature unspecified) underpin a phenotype, the mathematics of population genetics, while qualitatively analyzable, requires too many unknown parameters to make quantitatively testable predictions . The inadequacy of this approach is demonstrated by illustrations of the molecular pathways that generates traits : the network underpinning something as simple as growth may have forty or fifty participating proteins whose production involves perhaps twice as many DNA sequences, if one includes enhancers, splice variants etc. Theoretical genetics simply cannot handle this level of complexity, let alone analyse the effects of mutation.
We now know that there are at least 50 possible functions that DNA sequences can fulfill , that the networks for traits require many proteins and that they allow for considerable redundancy . The reality is that the evolutionary synthesis says nothing about any of this for all its claim of being grounded in DNA and mutation, it is actually a theory based on phenotypic traits. This is not to say that the evolutionary synthesis is wrong, but that it is inadequate - it is really only half a theory! Much as classical thermodynamics needed statistical mechanics to provide a theory of heat and work based on molecular physics, so the evolutionary synthesis needs to incorporate a proper model of DNA variation and a more sophisticated means of linking phenotypes to genotypes than Mendelian genetics. A modern version of the evolutionary synthesis thus has to be based on the reality of the genome and how it works in particular, it has to provide answers to three key questions about how organisms change.
How has genetic variation generated contemporary organism diversity and complexity from simple beginnings?
While the story of evolution is qualitatively different from that of the origin of life, it is important to distinguish between the origins of simple bacteria and of multicellular organisms that show cellular differentiation. The former is lost in the mist of time but it is remarkable that, in the comparatively short time between the appearance of Ediacaran organisms (c. 620 MYA) and those of the lower Cambrian (c. 530 MYA), a large number of novel cell types and tissue morphologies evolved, as can be seen in some of the early soft-bodied fossils such as Haikouella  This part of the origin of life should be within the remit of a good modern theory of evolution.
What controls the rate of evolution?
This area currently generates more heat than light! Selection pressure is part of the story but we do need some insight into why evolution sometimes seems to go very rapidly.
How is genetic variation manifested as phenotypic variation?
This last question meshes with a key problem of contemporary systems biology, one of whose aims is to work out how complex networks of proteins generate developmental and physiological functions and how mutation affects output.
Darwin's views on Lamarckian Heredity? - Biology
Number 2 works for me per molecular evolution and comparative biology. And I suppose 1 would need to show evidence of vitamin D problems in populations with high melanin.
And for a quick demonstration to MT readers on how to start looking for those sorts of data:
I have much the same experience in Intro to Biological Anthropology.
Hi Nick!! Thank you for telling me that. Whew :). Cheers!
Hi Holly, and Season's Greetings! It is always surprising when you think you've explained something and you think they got it, only to see the students have misunderstood it in their own way.
But, see how wonderful it can be? It can make you lie awake sweating in the middle of the night, doubting natural selection!
Excellent post. especially in terms of students' answers being somehow "intuitive." I think there is an important role here for popular science/media in terms of accurately explaining natural selection and evolutionary principles in general. We/they are not doing a very good job.
Regarding your question about loss of pigmentation in other species, is it possible that a lack of pigmentation is some kind of primitive "default" genetic state?
Thanks Pam! And that's an interesting idea. Anyone have any thoughts?
'Regarding your question about loss of pigmentation in other species, is it possible that a lack of pigmentation is some kind of primitive "default" genetic state?'
It's basic mathematics of molecular evolution, the synthetic theory. Adaptions that increased melanin accumulated in an environment that favored melanin. Then people migrated to an environment that no longer favored melanin, and natural selection no longer preserved melanin genes. I suppose that you can call this a default state while I suppose there was no melanin beneath early hominid hair. Of course, if we go back far enough, then second generation star dust is the default state.:)
I see nothing non-Darwinian about the loss of what's no longer favored by selection such as melanin and eyes of cave dwelling animals. Also, I know more about the synthetic theory than the writings of Darwin, but I couldn't imagine him seeing this as a non-Darwinian explanation. Does anybody know if Darwin himself predicted the loss of previously selected traits?
By the way, if there was significant advantage for the loss on melanin in colder climates, then positive natural selection helped to reduce melanin.
When I was first learning about evolution, I would always keep myself in check with Stephen Jay Gould's spandrels visualization. Is it the arch itself, or simply the shape that emerges when you put two arches together?
(Of course, Jeffrey Kurland, in his biocultural course, would later point to the medial cleft above his lips (the philtrum) and ask, "What the hell could this possibly be an adaptation to?" Same point, different pedagogy.)
And to Pam's point: the default genetic state would have to be exceedingly ancient. Pigmentation would have to be present in order for Archean-level cyanobacteria to take advantage of it in photosynthetic processes (probably). Going back earlier, to abiogenesis, well - who the hell knows? But certainly, organisms would be bombarded with solar radiation all this time, and would need some kind of defense.
Ugh, typo, "By the way, if there was significant advantage for the loss [of] melanin in colder climates, then positive natural selection helped to reduce melanin."
Also, in any case, Lamarckianism has to go while there's no need to lose sleep over the loss of ancestral traits that are no longer favored.:)
On a related note, the negative effects of low melanin in high UV regions is well known. I don't have the figures on me just now, but if you're interested, look up cancer and death rates among albino people in Tanzania. An extreme example, but possibly illustrative.
In many ways the key to all of this is the need to resist the juicy temptation to spin yarns that are difficult to test much less prove, and to accept that even if there is convincing evidence for selection on a trait, like skin color, the reasons may be multiple, variable, varying, and differing both within and between populations, and over time.
Doesn't make for good TV or simple story-telling, but it may make for more realistic science, and science is supposed to be our anchor to the realistic world. There are plenty of other fantasy worlds for anyone who craves that kind of fun to indulge in.
"It is difficult to imagine conditions of life more similar than deep limestone caverns under a nearly similar climate so that on the common view of the blind animals having been separately created for the American and European caverns, close similarity in their organisation and affinities might have been expected but, as Schiödte and others have remarked, this is not the case, and the cave-insects of the two continents are not more closely allied than might have been anticipated from the general resemblance of the other inhabitants of North America and Europe. On my view we must suppose that American animals, having ordinary powers of vision, slowly migrated by successive generations from the outer world into the deeper and deeper recesses of the Kentucky caves, as did European animals into the caves of Europe. We have some evidence of this gradation of habit for, as Schiödte remarks, 'animals not far remote from ordinary forms, prepare the transition from light to darkness. Next follow those that are constructed for twilight and, last of all, those destined for total darkness.' By the time that an animal had reached, after numberless generations, the deepest recesses, disuse will on this view have more or less perfectly obliterated its eyes, and natural selection will often have effected other changes, such as an increase in the length of the antennae or palpi, as a compensation for blindness. Notwithstanding such modifications, we might expect still to see in the cave-animals of America, affinities to the other inhabitants of that continent, and in those of Europe, to the inhabitants of the European continent. And this is the case with some of the American cave-animals, as I hear from Professor Dana and some of the European cave-insects are very closely allied to those of the surrounding country. It would be most difficult to give any rational explanation of the affinities of the blind cave-animals to the other inhabitants of the two continents on the ordinary view of their independent creation. That several of the inhabitants of the caves of the Old and New Worlds should be closely related, we might expect from the well-known relationship of most of their other productions. Far from feeling any surprise that some of the cave-animals should be very anomalous, as Agassiz has remarked in regard to the blind fish, the Amblyopsis, and as is the case with the blind Proteus with reference to the reptiles of Europe, I am only surprised that more wrecks of ancient life have not been preserved, owing to the less severe competition to which the inhabitants of these dark abodes will probably have been exposed."
(The Origin of Species Chapter 5: Laws of Variation by Charles Darwin )
Remember, Jim, that Darwin's view was Lamarckian in this context (use and disuse). In modern evolutionary biology we have a more correct explanation of the 'disuse' part: the inevitable mutational variation that will disrupt function if that disruption is not rejected by selection. If there is already variation in the relevant genes, it can increase in frequency by chance (genetic drift) to reduce the level of organization of a trait.
Loss of function by these paths can be discriminated from selection, in principle, by searching for evidence of reduced variation in the relevant genes (in those instances where they're known).
So if your point was that even Darwin knew that loss of selective maintenance would lead to loss of function, that is right, but it doesn't by itself tell us whether the loss was a positive adaptation to new environments, or was the rusting of old mechanisms that no longer matter.
Thanks, Ken. I forgot that Darwin occasionally invoked Lamarckianism.:) Perhaps that's why, as I stated earlier, I'm more familiar with the synthetic theory than the writings of Darwin: I never understood evolution until I carefully examined the basics of molecular evolution. Also, I completely agree with you when you say, "So if your point was that even Darwin knew that loss of selective maintenance would lead to loss of function, that is right, but it doesn't by itself tell us whether the loss was a positive adaptation to new environments, or was the rusting of old mechanisms that no longer matter."
And to add more to the mix, although I (and others) call the natural selection explanation for skin color and all traits that evolve through NS "Darwinian," well, Darwin's own explanation for skin color variation in Descent of Man wasn't all about natural selection! :) :) :)
Difference Between Darwin and Lamarck
The fascinating field of Evolutionary Biology has been extensively coloured by the two great scientists Darwin and Lamarck. They came up with theories to explain how the biological species have been evolving and those explanations really changed the classical way of thinking at that time. In fact, their inventions could be referred as blockbusters according to some well-honoured present-day scientists. That is because the existed conventional beliefs at that time got theoretically blasted after these scientists presented their theories to the world. This article intends to present the difference between Darwin and Lamarck, with special attention to the evolutionarily important findings.
Being a Fellow of the Royal Society, the English naturalist Charles Robert Darwin (1809 – 1882) is considered the Father of the Evolutionary Biology. He came up with the idea that the evolution of the biological species takes place according to the natural selection as the fittest one survives over others. Darwin presented some convincing evidence for his theory of evolution through the famous book of “On the Origin of Species” in 1959, and that had a lot of assistance from the scientist named Alfred Russel Wallace. Despite the debate about his theory of evolution in the 1870s, people respected and accepted it with the modern evolutionary approaches by scientists in 1930s – 1950s. The diversity of life could be well explained from his theory of evolution. The demand for the existence of variation among species by the nature could be well explained through his theory. According to Ecology, there are available niches in ecosystems that species (animals, plants, and all other species) have to adapt in order to survive. Therefore, the best-adapted species will survive through the challenges or demands by the nature. As Darwin explains his theory, the survival of the fittest takes place through natural selection. Apart from forming up this indisputable theory, Darwin authored many other popular publications at his time in the fields of Geology and Botany. As anyone would go through Darwin’s biography, it becomes evident that his father fancied making Darwin a doctor, but everyone else would have blessed him that he became an evolutionary biologist.
Jean-Baptiste Lamarck (1744 – 1829) was first a soldier then a brilliant biologist. He was born in France, became a soldier, honoured for his bravery, studied medicine, and involved with many biologically important publications during his time. Lamarck mastered his knowledge in both plants and animals, especially in the taxonomy of invertebrates. However, according to the present-day understanding about this great scientist, it is his theory of evolution that has struck hard into the minds of people over all other work he has done. As Lamarck explains how the evolution of species takes place, the use or disuse of characteristics matters for new characteristics that is, when a particular feature of an organism is being used extensively, the next generation would favour to increase the efficiency of that particular feature in order to adapt to the environment better. The characteristics that were acquired in one particular generation would pass or inherit to the next generation according to Lamarck. Therefore, it is known as the inheritance of acquired characteristics, and this theory of evolution was well accepted and honoured by the scientific world until Charles Darwin introduced the natural selection theory in the 19th century. Lamarck’s theory was the only sensible explanation for evolution during his time, and it is known as the Lamarckism.
What is the difference between Darwin and Lamarck?
• Darwin was an English scientist while Lamarck was a French biologist.
• Darwin proposed that evolution takes place by means of natural selection as the fittest one survives. However, Lamarck proposed that evolution takes place through inheritance of acquired characteristics.
• Darwinism is more accepted than Lamarckism by the present-day scientific community.
Darwin’s Critics: Then and Now
This image of Fleeming Jenkin, a leading critic of Darwinian evolution, comes from the 1899 edition of Memoir of Fleeming Jenkin, written by his former pupil Robert Louis Stevenson. Photograph by Edward B. Davis.
Darwin’s Unproven Hypothesis
Darwin had put forth his theory not as a proven fact, but as a probable hypothesis. He had inferred speciation hypothetically from evidence, not demonstrated it beyond all doubt. He was not naïve about the magnitude of the difficulties he faced in persuading skeptical colleagues who felt that his theory was simply too speculative, too far removed from hard observational facts. “Although I am fully convinced of the truth of the views given in this volume,” he stated honestly, “any one whose disposition leads him to attach more weight to unexplained difficulties than to the explanation of a certain number of facts will certainly reject my theory” ( Origin of Species , pp. 481-2 ). Indeed, many thought that he had gone too far, and in some cases Darwin even modified his theory in response to critics.
Enter Fleeming Jenkin
One of Darwin’s most astute critics, the Scottish engineer Fleeming Jenkin , was a man of many talents. Owner of thirty-five patents (mostly on telegraph cables and telpherage ), many in partnership with his close friend, the great physicist Lord Kelvin , Jenkin was a highly accomplished engineering professor. He also contributed to public health and did distinguished work on price theory , trade unions, and taxation , essentially originating graphical analysis of the law of supply and demand—not to mention essays about drama and stage productions.
A former religious skeptic turned Christian, Jenkin is probably best known today for his review of the second (1860) edition of The Origin of Species . Of the many objections he advanced, I will present three—all of which are still popular in one form or another with opponents of evolution.
Do Variations Accumulate Without Limit?
I’ll start with the very interesting argument that variations among animals and plants tend toward an asymptotic limit, denying the possibility of complete common ancestry. As Jenkin described it,
“Darwin’s theory requires that there shall be no limit to the possible differences between descendants and their progenitors, or, at least, that if there be limits, they shall be at so great a distance as to comprehend the utmost differences between any known forms of life. The variability required, if not infinite, is indefinite.”
In making his objection, Jenkin offered an example from breeding race horses—a common activity in the British Isles. “We all believe that a breeder, starting business with a considerable stock of average horses, could, by selection, in a very few generations, obtain horses able to run much faster than any of their sires or dams,” but eventually any improvements in speed would be almost negligible, despite the diligent efforts of many breeders to obtain the fastest horses. Overall, “the rate of variation in a given direction is not constant, is not erratic it is a constantly diminishing rate, tending therefore to a limit.”
Jenkin’s insistence on inherent limits for biological variation is echoed today when creationists say that biological variation must take place within the boundaries of the original created “kinds,” whatever they actually were . They do not agree with BioLogos that the genetic evidence for common ancestry is enormous —evidence entirely lacking to Darwin and Jenkin.
How Do New Organs Originate?
Jenkin added a second objection pertaining to variations: although natural selection might improve already existing biological organs, it cannot “create or develop new organs, and so originate species.” Jenkin believed that the formation of a new organ started with a sudden jump—the birth of a mutant individual, what was then called a “sport”. However, according to the non- Mendelian view of inheritance held by Darwin, Jenkin, and many others at the time, often called “ blending inheritance ,” any advantage associated with the unique trait of a single individual would be diluted every time it breeds with other individuals lacking that trait. In just a few generations, the effect would be “swamped” into insignificance, as the advantage resulting from the mutation is repeatedly cut in half.
Jenkin illustrated this point using the extremely racist example of a white man who finds himself shipwrecked on an island occupied by black people. According to Jenkin, even after many generations of interbreeding, the inhabitants of the island would still not be white quite the opposite: the presumed “physical strength, energy, and ability of a dominant white race” would gradually diminish. As Jenkin put it, “In the first generation there will be some dozens of intelligent young mulattoes, much superior in average intelligence to the negroes,” but over time “by degrees this advantage wanes.” (The egregious racism evidenced in this example–the only one he offered to illustrate this particular point–was common at that time.)
We now know that blending inheritance is wrong, and that Mendel’s work eliminates the problem of “swamping”. Once a given trait appears in a population, its associated gene(s) will be passed on and the trait can be expressed undiminished in future generations. For example, a person with piercing blue eyes who marries a person with brown eyes can have descendants with the same blue eyes. The trait is not “blended away” or diluted in the process of reproduction, whether or not it manifests itself in the very next generation.
Nevertheless, modern genetics does not erase all of the questions about how new organs can be formed by Darwinian evolution—as contemporary opponents of Darwinian evolution like to emphasize. For example, the book, Darwin’s Black Box (1996), written twenty years ago by biochemist Michael Behe , argued that no one had yet demonstrated exactly how Darwinian pathways could account for the “ irreducible complexity ” of the bacterial flagellum (a structure analogous to an outboard motor on a boat) or the immune system. However, we now know that neither the flagellum nor the immune system is irreducibly complex. Even something as complex as the mammalian eye can be understood in terms of Darwinian evolution .
Not Enough Time for Evolution to Happen
The age of the Earth could not be calculated very precisely until around the time when Darwin published The Origin . Geologists had known for decades that the Earth must be enormously older than the traditional biblical timescale of a few thousand years, but they didn’t agree on any particular estimate. From Charles Lyell Darwin had acquired a vague sense of the vast antiquity of the Earth, but in The Origin we find just one place where he assigned a specific number to a geological process. According to Darwin, about 300 million years was needed to form the Weald , the chalky region in southeastern England that culminates in the famous white cliffs of Dover. It was in fact a crude, back-of-the-envelope calculation, yet he said that it “must have required 306,662,400 years,” implying a precision that simply wasn’t there and leaving the reader with the impression that the Earth itself was even far older, old enough to allow for evolution to proceed at a snail’s pace ( Origin , p. 287).
Geological map of southeastern England, from the third volume of Charles Lyell, Principles of Geology (1833), showing the region known as the Weald in full color. Lyell argued that the present landscape had been formed when higher chalky hills had slowly eroded away, a process he called “denudation.” He didn’t give an estimate of the time taken for that process, but his disciple Darwin did in The Origin. Image courtesy of History of Science Collections, University of Oklahoma Libraries.
This did not convince Jenkin, whose quantitative skills far exceeded Darwin’s. He drew on state-of-the-art calculations by his friend Lord Kelvin, establishing the range of possible ages for the Earth and the Sun. The Earth, he believed, was between 20 and 400 million years old, most likely about 98 million years old the Sun was probably about 100 million years old, with an upper limit of 500 million years. If Kelvin was right, then Darwin was wrong: there wasn’t nearly enough time for evolution to have happened as Darwin conceived it.
Subsequently, however, we’ve learned that the Earth is billions of years old, nullifying Jenkin’s objection. Of course, we can’t blame Jenkin for being ignorant. Indeed we should credit him for granting the abstract possibility that “it may please the Creator to continue creating energy in the form of heat at the centre of the sun and earth…” He simply had no way to know that the Creator was doing exactly that, by putting nuclear fusion inside the Sun and radioactive decay inside the Earth.
Old-earth creationists today accept an ancient Earth , but still doubt that evolution could have produced the full range of living things without some acts of special creation. Young-earth creationists obviously reject the standard timescale entirely. However, they actually agree that natural selection can form new creatures—even far more rapidly than evolutionists grant—but (again) only within created “kinds.”
Jenkin’s Conclusion and Darwin’s Response
At the end of his review, Jenkin stated his conclusion succinctly: “A plausible theory should not be accepted while unproven and if the arguments of this essay be admitted, Darwin’s theory of the origin of species is not only without sufficient support from evidence, but is proved false by a cumulative proof.”
How did Darwin respond to arguments like these?
Darwin didn’t know how to refute Kelvin’s arguments about limited time—and he was really concerned about them, telling Alfred Russel Wallace in 1869 that “ Thompson’s views of the recent age of the world have been for some time one of my sorest troubles .” Darwin thought he was still correct, but he could not back it up with a formal quantitative argument. Therefore, starting with the third edition of The Origin in 1861—even before Jenkin wrote his review of the second edition—he ducked the issue by removing the part about the denudation of the Weald.
Ignorant of Mendel’s work and looking for ways to quicken the process of evolution, especially if the Earth is really much younger than he thought, Darwin introduced his theory of “ pangenesis ” in another book, The Variation of Animals and Plants Under Domestication (1868). He postulated that particles called “ gemmules ” would be emitted by parts of the body and circulate through the bloodstream to the reproductive organs, where they would accumulate and influence heredity. In that way, characteristics acquired by an individual organism during its lifetime could perhaps be inherited by its offspring, enabling evolution to work faster that it would otherwise. The inheritance of acquired characteristics is usually associated more with one of Darwin’s predecessors, the French marine biologist Lamarck , than with Darwin, but Darwin nevertheless used that idea to some extent.
For several decades other scientists proposed various Lamarckian ideas, underscoring an irony: although Darwin’s evidence eventually convinced others to accept evolution, the most widely accepted varieties of evolution at the time were neo-Lamarckian. Darwinian evolution, driven primarily by natural selection operating on “random” variations, did not gain the allegiance of a majority of scientists until around 1930. This phenomenon has been called “the eclipse of Darwinism ,” but exploring that topic would take us well beyond the scope of this series.
Today, the vast majority of biologists and geologists, whether or not they are Christians, believe that Darwin’s central idea was right—widely diverse organisms are related through common ancestry, and natural selection is a primary cause of that diversity. Many of the explanatory problems that Darwin, Jenkin, and others found in certain details of his theory have been solved or made irrelevant by subsequent scientific discoveries.
Overall, the story of Darwin and his theory shows that details matter—not only in science, but also in history. Darwin didn’t invent the idea of evolution and did not believe it at first, but he came round to it after extensive observations and experiences on a five-year voyage around the world led him to wonder about the “ mystery of mysteries ”—the origin of new creatures through vast geological ages. Drawing key insights from economic theory , he conceived a new type of evolutionary theory driven by competition for scarce resources—all the while viewing it as a process of creation by natural law .
Even if Darwin wasn’t right about every single detail, he was right about the big picture: God does indeed create many things in ways that are not entirely above human understanding. We should rejoice and be glad in this: the study of evolution is just one more way to think God’s thoughts after him.