Human evolution theory utilizing concepts of neoteny & female sexual selection
An etiology of neuropsychological disorders such as autism and dyslexia, and the origin of left handedness.

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Charles Darwin

Charles Darwin: bibliographical excerpts


"Though he regarded these "Lamarckian" instruments as no longer central to the production of new species, he did retain them as various auxiliary mechanisms in the Origin of Species. So, for instance, anatomical changes produced through acquired habit could, as he yet maintained in the Origin, become impressed upon the hereditary substance and be passed to succeeding generations; as well, such acquired characteristics might also serve as variations upon which natural selection could operate. ... In the Origin, Darwin listed use and disuse among the sources of variation for selection. He said: "From the facts alluded to in the first chapter, I think there can be little doubt that use in our domestic animals strengthens and enlarges certain parts, and disuse diminishes them: and that such modifications are inherited." See Charles Darwin, On the Origin of Species (London: Murry, 1859), p. 134. He also asserted that acquired habit, like selection, could act more immediately to introduce adaptations; but he yet thought his primary device would always retain the upper hand (ibid, pp. 142-43): "On the whole, I think we may conclude that habit, use, and disuse, have, in some cases, played a considerable part in the modification of the constitution and of the structure of various organs: but that the effects of use and disuse have often been largely combined with, and sometimes over-mastered by, the natural selection of innate differences." (Richards, RJ (1992) The Meaning of Evolution. Univ of Chicago Press: Chicago p. 84)

"There are other candidates for units of selection --- organisms, groups, species. Organisms are the most likely candidate. But an organism does not replicate facsimiles of itself: its offspring cannot inherit its acquired characteristics, the accidental changes that it has undergone during its lifetime. Similar considerations hold, though even more strongly, for groups and other higher levels. Although in some loose sense they renew themselves, divide, bud off, persist, nevertheless they cannot be true replicators. They have no reliable means of self-propagation, no more or less automatic mechanism for churning out generation after generation of facsimilies. Genes, then, can be replicators whereas organisms, groups and other levels in the hierarchy cannot. Natural selection is about the differential survival of replicators. So genes are the only serious candidates for units of selection." (Cronin, Helena (1992) The Ant and the Peacock: Cambridge Univ. Press, Cambridge p. 287)

"In simplest terms, evolution by natural selection proceeds, as the French biologist Jacques Monod once put it (rephrasing Democritus), by chance and necessity. Different forms of the same gene, called alleles, originate by mutations, which are random changes in the long sequences of DNA (deoxyribonucleic acid) that compose the gene. In addition to such point-by-point scrambling of he DNA, new mixes of alleles are created each generation by the recombining processes of sexual reproduction. The alleles that enhance survivial and reproduction of the carrier organisms spread through the population, while those that do not, disappear. Chance mutations are the raw material of evolution. Environmental challenge, deciding which mutants and their combinations will survive, is the necessity that molds us further from this protean genetic clay." (Wilson, E.O. (1998) Consilience. Knoff, New York p. 129)

"For principled and substantially philosophical reasons, based largely on his reform of natural history by inverting the Paleyan notion of overarching and purposeful beneficence in the construction of organisms, Darwin built his theory of selection at the single causal level of individual bodies engaged in unconscious (and metaphorical) struggle for their own reproductive success. But the central logic of the theory allows selection to work effectively on entities at several levels of a genealogical hierarchy, provided that they embody a set of requisite features for defining evolutionary individuality. Genes, cell lineages, demes, species, and clades-as well as Darwin's favoured organisms-embody these requisite features in enough cases to form important levels of selection in the history of life. R. A. Fisher explicitly recognized the unassailable logic of species selection, but denied that this real process could be important in evolution because, compared with the production of new organisms within a species, the origin of new species is so rare, and the number of species within most clades so low. I review this and other classical arguments against higher-level selection, and conclude (in the first part of this paper) that they are invalid in practice for interdemic selection, and false in principle for species selection. Punctuated equilibrium defines the individuality of species and refutes Fisher's classical argument based on cycle time. In the second part of the paper, I argue that we have failed to appreciate the range and power of selection at levels above and below the organismic because we falsely extrapolate the defining properties of organisms to these other levels (which are characterized by quite different distinctive features), and then regard the other levels as impotent because their effective individuals differ so much from organisms. We would better appreciate the power and generality of hierarchical models of selection if we grasped two key principles: first, that levels can interact in all modes (positively, negatively, and orthogonally), and not only in the negative style (with a higher level suppressing an opposing force of selection from the lower level) that, for heuristic and operational reasons, has received almost exclusive attention in the existing literature; and second, that each hierarchical level differs from all others in substantial and interesting ways, both in the style and frequency of patterns in change and causal modes." (Gould SJ (1998) Gulliver's further travels: the necessity and difficulty of a hierarchical theory of selection. Philos Trans R Soc Lond B Biol Sci;353(1366):307-14)

"Weismann recognized an important and unequal cellular dichotomy: Germ-line (or sex) cells create both the sex cells and the somatic (or body) cells of offspring individuals. The implication is enormous: What happens to the cells of an individual's body, its somatic cells, during its lifetime cannot affect its sex cells, which are present from an early stage in development. In a single blow, Weismann removed the possibility of the inheritance of acquired characteristics. That notion had been the linchpin of Lamarck's evolutionary mechanics, and was adopted even by Darwin in the sixth edition of the Origin as he tried to placate his critics." (Eldredge, Niles (1999) The Pattern of Evolution. W. H. Freeman: New York p. 121)

"The argument that a favorable mutative sport would be "utterly outbalanced by numerical inferiority." Since the unblending character of Mendelian units was unknown, Jenkin's position was simply that a single favorable mutation would soon be swamped out by degrees obliterated in any population group in which it occured. Since the favored animal of plant would presumably be mating with its normal fellows, the rare variation would not long survive. As a potent example Jenkin advanced the hypothetical case of a single well-endowed white man being cast ashore on a island inhabited by Negroes. No matter how much power he might attain among them, the tribe would certainly not become white because of his presence." (Eiseley, L (1958) Darwin’s Centry. Anchor Books: New York p. 215)

"The retreat of the geologists placed Darwin in a difficult position, because he simply could not accept Kelvin's estimate of a hundred million years (Burchfield, 1974). He had no positive arguments to offer in the realm of physics, but insisted that the estimates he and Lyell had been making could not be in error to the extent implied. To the end of his life, Darwin believed that there was something wrong with Kelvin's calculations, but he had nothing to back up his belief. Even other evolutionists such as Wallace and Huxley began to accept the idea that evolution must have taken place more rapidly than they had at first thought possible." (Bowler PJ (1984) Evolution, The History of an Idea. Univ of California Press: Berkeley p. 195)

"Sexual selection depends on the success of certain individuals over others of the same sex, in relation to the general conditions of life. The sexual struggle is of two kinds; in the males, in order to drive away or kill their rivals, females remaining passive; whilst in the other, the struggle is likewise between the individuals of the same sex, inorder to excite or charm those of the opposite sex, generally the females, which no longer remain passive, but select the more agreeable partners. This latter kind of selection is closely analogous to that which man unintentionally, yet effectually, brings to bear on his domesticated productions, when he preserves during a long period the most pleasing or useful individuals, without any wish to modify the breed." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 636-8)

"In earlier studies of sexual selection, the emphasis was heavily on the male competition and indeed selection does seem to work most spectacularly here. But it has more recently been seen that female choice may well be the ultimate determinant of the route selection will take. The males, as it were, exhaust themselves on competition, then the female groups pick out the winners as studs. Once it is realised that there can thus be considerable difference in reproductive success between the different female groups, the full dynamics of the system can be understood. The females' strategy has to be to pick the 'best' male, whatever the criteria. If a group of females can become inseminated by superior male genes, not only do their female offspring get the immediate advantages, but the chance of their 'sons' inseminating many groups of females itself increases. Thus, the genes of the original female kin-group will spread in the total population more successfully than those of rival groups. If we paraphrase Samuel Butler's famous statement (that a chicken is the egg's way of making another egg) and say that a male is the female's way of making more females (or that a male is the female kin-group's way of making another female kin-group) then we are getting close to the heart of the sexual selection process. But we have to see it, ultimately, as the stategy of the genes to produce replicas of themselves." (Fox, R (1983) Sexual selection, female choice and human kinship. Cambridge Anthropology 8,3: pp. 6-7)

"So, when a woman proceptively approaches this man and not that, she has de facto made a selection. On the other hand, if the man approaches her, she also decides to accept or reject. If, for whatever her reasons, she finds him "uninteresting" and turns away, she has selected him out. Or, if she responds positively to him, she has given him a chance to proceed. Either way, she makes the choice." (Perper, Timothy (1989) Theories and observations on sexual selection and female choice in human beings. Medical Anthropology 11(4): pp. 416)

"I suggest that most evolutionary innovations become established in populations by sexual selection through mate choice, or, perhaps more commonly, arise as phenotypic side-effects of sexually-selected traits. These novelties could be called "courtship innovations..... This theory is consistent with most important facts of speciation and evolutionary innovation, and it explains several otherwise baffling phenomena. It is consistent with the view that species are natural kinds that define themselves through mate choice criteria (e.g. Paterson, 1985), and with the punctuated equilibrium view (Eldredge & Gould, 1972; see Eldredge, 1989) that most evolutionary change in economic traits is closely correlated with evolutionary change in reproductive traits---i.e. directional natural selection operates most strongly around speciation events, when sexual selection also operates most strongly" (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 133)

“The relative parental investment of the sexes in their young is the key variable controlling the operation of sexual selection. Where one sex invests considerably more than the other, members of the latter will compete among themselves to mate with members of the former. Where investment is equal, sexual selection should operate similarly on the two sexes. The pattern of relative parental investment in species today seems strongly influenced by the early evolutionary differention into mobile sex cells fertilizing immobile ones, and sexual selection acts to mold the pattern of relative parental investment. The time sequence of parental investment analyzed by sex is an important paramenter affecting species in which both sexes invest considerable parental care: the individual initially investing more (usually the female) is vulnerable to desertion. On the other hand, in species with internal fertilization and strong male parental investment, the male is always vulnerable to cukoldry. Each vulnerability has led to the evolution of adaptations to decrease the vulnerability and to counter-adaptations. Females usually suffer higher mortality rates than males in monogamous birds, but in nonmonogamous birds and all other groups, males usually sugger high rates. The chromosomal hypothesis is unable to account for the data. Instead, an adaptive interpretation can be advanced based on the relative parental investment of the sexes. In species with little or no male parental investment, selection usually favors male adaptations that lead to high reproductive success in one or more breeding seasons at the cost of increased mortality. Male competition is such species can only be analysed in detail when the distribution of females in space and time is properly described. Data from field studies suggest that in some species, size, mobility, experience and metabolic rate are important to male reproductive success. Female choice can augment or oppose mortality selection. Female choice can only lead to runaway change in male morphology when females choose by a relative rather than absolute standard, and it is probably sometimes adaptive for females to so choose. The relative parental investment of the sexes affects the criteria of female choice (and of male choice). Throughout, I emphasize the criteria that sexual selection favors different male and female reproductive strategies and that even when ostensibly cooperating in a joint task male and female interests are rarely identical.” (Parental investment and sexual selection (1972) Robert L. Trivers in Sexual selection and the descent of man 1871-1971 Campbell, Bernard (ed.) pp. 173)

"In regard to structures acquired through ordinary or natural selection, there is in most cases, as long as the conditions of life remain the same, a limit to the amount of advantageous modification in relation to certain special purposes; but in regard to structures adapted to make one male victorious over another, either in fighting or in charming the female, there is no definite limit to the amount of advantageous modification; so that as long as the proper variations arise the work of sexual selection will go on. This circumstance may partly account for the frequent and extraordinary amount of variability presented by secondary sexual characters. Nevertheless, natural selection will determine that such characters shall not be acquired by the victorious males, if they would be highly injurious, either by expending too much of their vital powers, or by exposing them to any great danger. The development, however, of certain structures---of the horns, for instance, in certain stags---has been carried to a wonderful extreme; and in some cases to an extreme which, as far as the general conditions of life are concerned, must be slightly injurious to the male. From this fact we learn that the advantages in battle or courtship, and thus leaving a numerous progeny, are in the long run greater than those derived from rather more perfect adaptation to their conditions of life. We shall further see, and it could never have been anticipated, that the power to charm the female has sometimes been more important than the power to conquer other males in battle." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 235)

"The contrast between non-social and social selective forces was reflected in Darwin's idea that, whereas natural selection would more or less grind to a halt in a constant environment, sexual selection was, in principle, capable of continuing indefinitely on its giddy spiral of ornamental exaggeration: 'In regard to structures acquired through ordinary or natural selection, there is in most cases, as long as the conditions of life remain the same, a limit to the amount of advantageous modification in relation to certain special ends; but in regard to structures adapted to make one male victorious over another, either in fighting or in charming the female, there is no definite limit to the amount of advantageous modification; so that as long as the proper variations arise the work of sexual selection will go on.' (Darwin 1871, i, p. 278) (Cronin, Helena (1992) The Ant and the Peacock: Cambridge Univ. Press, Cambridge p. 233)

"A possible explanation might be that feathers developed as a sexual display, scales being elaborated by the males for color and shininess. Feathers not only retain warmth and make an excellent aerodynamic surface but also serve for show, often being brilliantly colorful and iridescent. Many birds--from the gorgeous quetzal and birds of paradise to gaudily colored ducks -- have spectacular displays." (Wesson, Robert (1991) Beyond Natural Selection. MIT Press: Cambridge p. 48)

"All these facts with respect to music and impassioned speech become intelligible to a certain extent, if we may assume that musical tones and rhythm were used by our half-human ancestors, during the season of courtship, when animals of all kinds are excited not only by love, but by the strong passions of jealousy, rivalry, and triumph. From the deeply-laid principle of inherited associations, musical notes in this case would be likely to call up vaguely and indefinitely the strong emotions of a long-past age. As we have every reason to suppose that articulate speech is one of the latest, as it certainly is the highest, of the arts acquired by man, and as the instinctive power of producing musical notes and rhythms is developed low down in the animal series, it would be altogether opposed to the principle of evolution, if we were to admit that man's musical capacity has been developed from the tones used in impassioned speech. We must suppose that the rhythms and cadences or oratory are derived from previously developed musical powers. We can thus understand how it is that music, dancing, song, and poetry are such very ancient arts. We must go even further than this, and, as remarked in a former chapter, believe that musical sounds afforded one of the bases for the development of language." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 593)

"With respect to the origin of articulate language, after having read on the one side the highly interesting works of Mr. Hensliegh Wedgwood, the Rev. F. Farrar, and Prof. Schleicher, and the celebrated lectures of Prof. Max Muller on the other side, I cannot doubt that language owes its origin to the imitation and modification of various natural sounds, the voices of other animals, and man's own instinctive cries, aided by signs and gestures. When we treat of sexual selection we shall see that primeval man, or rather some early progenitor of man, probably first used his voice in producing true musical cadences, that is in singing, as do some of the gibbon-apes at the present day; and we may conclude from a widely-spread analogy, that this power would have been especially exerted during the courtship of the sexes,---would have expressed various emotions, such as love, jealously, triumph,---and would have served as a challenge to rivals. It is, therefore, probable that the imitation of musical cries by articulate sounds may have given rise to words expressive of various complex emotions. The strong tendency in our nearest allies, the monkeys, in microcephalous idiots, and in the barbarous races of mankind, to imitate whatever they hear deserves notice, as bearing on the subject of imitation. Since monkeys certainly understand much that is said to them by man, and when wild, utter signal-cried of danger to their fellows; and since fowls give distinct warnings for danger on the ground, or in the sky form hawks (both, as well as a third cry, intelligible to dogs), may not some unusually wise ape-like animal have imitated the growl of a beast of prey, and thus told his fellow-monkeys the nature of the expected danger? this would have been a first step in the formation of a language." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 89-90)

"Since, in comparison with genetic transmission, social transmission typically results in a more rapid diffusion of a preference through a population, culturally generated sexual selection may be unusually fast, and the alleles underlying favored traits may be selected to high frequency in just a handful of generations. This analysis suggests that (1) there should be local, society-specific correlations between favored traits and mating preferences; (2) sexual selection may account for cross-cultural variation in traits underlying attractiveness; and (3) recent selection may have modified any predilections favored throughout the Pleistocene." (Laland KN (1995) reply to.... Sexual selection, physical attractiveness, and facial neoteny: cross-cultural evidence and implications. Current Anthropology 36 (5): 728-9)

"Many will declare that it is utterly incredible that a female bird should be able to appreciate fine shading and exquisite patterns. It is undoubtedly a marvellous fact that she should possess this almost human degree of taste. He who thinks that he can safely guage the discrimination and taste of the lower animals may deny that the female Argus pheasant can appreciate such refined beauty; but he will then be compelled to admit that the extraordinary attitudes assumed by the male during the act of courtship, by which the wonderful beauty of his plumage is fully displayed, are purposeless; and this is a conclusion which I for one will never admit." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 412)

"It would even appear that mere novelty, or slight changes for the sake of change, have sometimes acted on female birds as a charm, like changes of fashion with us." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 511)

"Two recent experiments support the idea that females simply have idiosyncratic tastes that have not evolved. Male grackles---blackish birds of medium size---sing only one kind of song. Female grackles prefer to mate with males that sing more than one kind of song. William Searcy of the University of Pittsburgh discovered why. He made use of the fact that a female grackle will go up to singing loudspeakers and adopt a soliciting posture as if waiting to be mated. Her tendency to do so declines, however, as she gets bored with the song. Only if the loudspeaker starts singing a new song will her soliciting start afresh. Such "habituation" is just a property of the way brains work; our senses, and those of grackles, notice novelty and change, not steady states. The female preferences did not evolve; it just is that way." (Ridley 1993: 164-5, The Red Queen)

"...the only consistent interest seen among the general primate population is an interest in novelty and variety. Although the possibility of choosing for good genes, good fathers, or good friends remains an option to female primates, they seem to prefer the unexpected." (Small, Meredith F. (1993) Female choices: Sexual behavior of female primates. Cornell Univ. Press, Ithaca, 1993 pp. 153)

"This interest in novelty has been clearly documented for twelve species of primates (Small 1989). But more striking is the regularity with which females choose these males. Female chimps leave their natal group, copulate with neighboring males, and then return; patas monkey females roam the savannah looking for males other than their harem leader; squirrel monkey females seek extratroop males; monogamous gibbons also look to neighbors. In fact, the search for the unfamiliar is documented as a female preference more often than is any other characteristic our human eyes can percieve. Perhaps these females are concerned with inbreeding, and seeking new males is an easy way to ensure a mixture of genes for the offspring. Females, rather than males, should be the most worried about inbreeding because they have the largest investment in each conception (Huffman 1993). Their interest in novelty, therefore, might be a primitive urge to find mates lurking at the periphery of their group with genes different, but not completely different, from their own. Suzanne Ripley has suggested that avoiding inbreeding and gaining genetic diversity would be especially important in multimale-multifemale groups in which a ability to adapt in a changing world is paramount (1980). The evidence that this might be true comes from the genetic makeup of the animals themselves. Rhesus monkeys, perhaps the most evolutionarily successful primate after humans, are also highly genetically diverse (Melnick, Pearl, and Richard 1984, Ober et al. 1984). Although other authors have attributed this genetic diversity solely to male migration, it may be that females are more responsible in that they prefer to mate with outside males and place a forward spin on male transfer (Lindburg 1969, L.M. Wolfe 1986). In this sense, female choice is not a matter of females' choosing some males over others and making an impact on the genetic component of future generations, especially of their own offspring. For rhesus, Japanese macaques, and baboons, and perhaps for other nonhuman primates, the entire social system may be driven by what females prefer. The power of female choice, in this instance, is not just for mating--it exerts a potent evolutionary force on the entire social system." (Small, Meredith F. (1993) Female choices: Sexual behavior of female primates. Cornell Univ. Press, Ithaca, 1993 pp. 171-2)

"Novelty can mean three general things in relation to mate choice: attraction to new physical traits, attraction to new individuals, or attraction to new behaviors. Of these, Darwin focused on the first, briefly discussed the second, and mostly overlooked the third. Although Darwin emphasized the emergence of new traits across individuals, neophilia could also favor individuals who can regularly generate interesting new behaviors. This is why neophilia may be relevant to human encephalization, which represents largely the evolution of new mental capacities for protean (ever-changing, ever-new) courtship displays." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 370)

"Sense of Beauty.---This sense has been declared to be peculiar to man. I refer here only to the pleasure given by certain colors, and sounds, and which may fairly be called a sense of the beautiful; with cultivated men such sensations are, however, intimately associated with complex ideas and trains of thought. When we behold a male bird elaborately displaying his graceful plumes or splendid colors, before the female, whilst other birds, not thus decorated, make no such display, it is impossible to doubt that she admires the beauty of her male partner. As women everywhere deck themselves with these plumes, the beauty of such ornaments cannot be disputed. As we shall see later, the nests of humming-birds, and the playing passages of bower-birds are tastefully ornamented with gaily-colored objects; and this shows that they must receive some kind of pleasure from the sight of such things. With the great majority of animals, however, the taste for the beautiful is confined, as far as we can judge, to the attractions of the opposite sex." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 95)

"Darwin (1871) observed that, whatever morphological traits have been elaborated through sexual selection, male animals typically use special behaviors to display these traits to females in courtship. The conspicuous presentation, waving, vibrating, and directing of horns, wattles, and tails towards females was among Darwin's strongest evidence that these traits did in fact evolve through sexual selection. Rarely does one observe a sexually-selected morphological trait tht is not displayed with some special behavior during courtship. This implies that, once an exaggerated morphological trait exists, the evolution of special behaviors that display it to best advantage can evolve fairly quickly and easily. Thus, we have indirect evidence that behavioral courtship displays are particularly likely to evolve under sexual selection." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 126)

" It is also remarkable that birds which sing well are rarely decorated with brilliant colors or other ornaments. ... Hence bright colors and the power of song seem to replace each other." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 383)

"With respect to female birds feeling a preference for particular males, we must bear in mind that we can judge of choice being exerted only by analogy. If an inhabitant of another planet were to behold a number of young rustics at a fair courting a pretty girl, and quarrelling about her like birds at one of their places of assemblage, he would, by the eagerness of the wooers to please her and to display their finery, infer that she had the power of choice. Now with birds the evidence stands thus: they have acute powers of observation, and they seem to have some taste for the beautiful both in color and sound. It is certain that the females occasionally exhibit, from unknown causes, the strongest antipathies and preferences for particular males." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 434)

"As the body in woman is less hairy than in man, and as this character is common to all races, we may conclude that it was our female semi-human ancestors who were first divested of hair, and that this occured at an extremely remote period before the races had diverged from a common stock. Whilst our female ancestors were gradually acquiring this new character of nudity, they must have transmitted it almost equally to their offspring of both sexes whilst young; so that its transmission, as with the ornaments of many mammals and birds, has not been limited either by sex or age. There is nothing surprising in a partial loss of hair having been esteemed as an ornament by our ape-like progenitors, for we have seen that innumerable strange characters have been thus esteemed by animals of all kinds, and have consequently been gained through sexual selection. Nor is it surprising that a slightly injurious character should have been thus acquired; for we know that this is the case with the plumes of certain birds, and with the horns of certain stags." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 623)

“Young women appear to be attractive to young men owing to the combination of paedomorphic and secondary sexual signal characteristics which they present to them initially at a distance. Hairlessness, voice tone, complexion and girlish behavior all have a childlike character that in ethnological terms appear to lower the probability of a male aggressive response of to appease if one is present. These same characteristics are likely to reduce male fear and anxiety on closer approach and to permit sexual expression. The male begins to display in various “show-off” performances including physical prowess (such as, dancing), exhibitions of virtuosity in the social graces, in demonstrations of charm and sensitive virility. These displays attract the female’s attention and provide the basis upon which she may choose to respond to or reject the male’s approach: or more usually, simply fail to observe them. ... From the purely ethological viewpoint this sequence has much in common with courtship in birds and often mammals....” (Sexual selection in the primates (1972) John H. Crook in Sexual selection and the descent of man 1871-1971 Campbell, Bernard (ed.) pp. 274)

"We do have data from Japan that are highly suggestive. Here, for many centuries, fair skins have been under parental control and, other things being equal, parents seek attractive brides for their sons. As elsewhere, members of the upper classes tend to be the luckiest. This might be expected to lead to selection as the generations have gone by. Research which I conducted a few years ago (Hulse 1967) indicated that this has taken place, for upper-class high school students have the fairest skins and those of the lower class the darkest, while middle-class students are intermdiate in pigmentation. Furthermore, data from Greece (Friedl 1962) indicate that girls who are considered good-looking marry earlier than, and need not be supplied with as large a dowry as, their less-attractive sisters. Throughout southern Europe, the upper classes contain a disproportionate number of blondes and near-blondes. Sexual preferences, though they may be based on social snobbery rather than aesthetic interest, are capable of shifting allele frequencies in human population." (Hulse, F.S. (1978) Group selection and sexual selection in human evolution. in Evolutionary models and studies (Hague) Meier, R., Otten, C.M., Abdel-Hameed, F. (eds.), Moulton Publisher, Paris. p. 33)

"Two characters could hardly be wider apart than the size and development of man's brain and the distribution of hair upon the surface of his body, yet they both lead us to the same conclusion---that some other power than natural selection has been engaged in his production." (Wallace 1895: 197, Natural Selection)

"Edward Westermarck in his early classic A Short History of Marriage (1968: 126-155) discussed consent as a condition for marrige. Females, he noted, most often were married off at the will of some male-father, family elders, uncle. It is to be noted that the male partner in such marriages, also, had little personal choice. However, Westermarck pointed out that females in the simplest hunting and gathering societies could - and did - refuse the assigned mate. Sometimes she could do this directly and in other societies by subtle, indirect action. She lost much of this freedom in technologically more advanced societies. Some of the strongest arguments against male dominant choice of females as sex partners can be found in the statistical, cross-cultural work of George Murdock (1949: 20-21). Out of 241 societies where his criteria could be applied, 163 involved some consideration: bride-price, bride service, or exchange of women. In other words, families made the decisions rather than the individuals involved. Regarding divorce, Murdock (1969: 175-76) found, somewhat surprisingly, that in thirty of forty societies there were no substantial differences in the rights of men and women to terminate a marriage. Only 15 percent actually had the stereotyped view where men controlled the action. If divorce involved equal female choice, isn't it likely that she would have had much to say about the original marriage? Further analysis of mating practices in primitive society raises more questions as to male choice selecting for spedific traits. Murdock's worldwide sample of 25o societies (1949:263) showed that only three had a generalized sex taboo. Most of the others allowed premarital sex, extra-marital sex, wife-lending, etc., all of which could be involved in pregnancy with someone other than the social father." (Smith, James M. (1976) Sexual selection in recent human populations. California Anthropologist 6 (1): pp. 20)

"We do not know why men have conspicuous genitals, but a male chimp solicits a female by opening his legs, displaying an erect penis and flicking his phallus with a finger as he gazes at a potential partner. A prominant, distinctive penis helps broadcast one's individuality and sexual vigor, which may lure female friends. In many species of insects and primates, males have exceptionally elaborate penises, and scientists think these evolved specifically because females chose those males with elaborate, sexally stimulating genitals. So perhaps as Lucy's ancestors became bipedal some four million years ago, males began to parade their genitals in order to make special friends with favored females--selecting for those with large organs." (Fisher, H. (1992) Anatomy of Love: The Mysteries of Mating, Marriage, and Why We Stray. Simon & Schuster, New York, 1992. pp. 177)

"Roger Short...had predicted that in {primate} species where females mate with more than one male during a reproductive cycle, the males would have larger testes for their body size than in species whose females had only a single mate per cycle. When the females were promiscous, the sperm of each male would have to compete with those of other males, and the male producing the most sperm was most likely to generate offspring. [quote from] (Harvey and Clutton-Brock 1983, p. 315" (Cronin, Helena (1992) The Ant and the Peacock: Cambridge Univ. Press, Cambridge p. 97)

"One characteristic among primates has been clearly targeted for possible selection by Fisherian female choice--male penis size. Primate males living in groups with many females and many males, groups in which promiscuity is the mating rule, have long penes (Dixon 1978). Male chimps, in fact, use their penes for display toward estrous females. Because a longer penis would give a female pleasure (note that the human male has the longest and thickest penis of any primate), female choice might have been a factor driving penis length to extremes among primates." (Small, Meredith F. (1993) Female choices: Sexual behavior of female primates. Cornell Univ. Press, Ithaca, 1993 pp. 109)

"Rampant female mating leads to competition not before but after copulation, not among bodies but among sperm. A female copulates with several males whose sperm compete to fertilize her. Sperm competition can occur even if a female copulates with different males several days apart. This is because sperm are hardy and may survive in the vagina of a chimpanzee or woman for as long as eight or nine days. Any female who copulates with more than a single male while ovulating opens the gates to a sperm race. The males or men who produce the sperm are not direct entrants; they are more like corporate sponsors advertising their name and providing financial backing. Not all participants in the all-male marathon are equally prepared to win. Mammals who mate more frequently, and produce more sperm per ejaculation, are more likely to impregnate their partners. Favoring the sperm of one male over that of competitors are such things as position during intercourse, force and timing of pervic thrusting, number and speed to ejaculated sperm, and proximity of the spermatic means of delivery---the penis---to the egg at time of ejacultion. Copious sperm production (estimated by testicle weight), deep penetration, and an elongated penis are all presumably advantages to males engaged in sperm competition. Perhaps most important is sheer sexual vigor, with more active males ejaculating the greatest number of times gaining a competitive edge. The charm and proficiency of a male---his ability to seduce a female and to continue to please after seducing her---of course also crucially determine his chances of entering and therefore of winning the competition; and in this sense females make the great impact of generally deciding who will and will not compete. There is also evidence that a woman who climaxes while making love to her lover is more likely to become pregnant by him." (Margulis, L & Sagan, D. (1991) Mystery Dance, On the Evolution of Human Sexuality: Summit Books, New York pp. 37)

"More convincing vestiges of a sexual selective history in which females mated polyandrously can be found in the human male. Perhaps the clearest such vestige is testis size (Short, 1977). Men's testes are substantially larger, relative to body size, than those of gorillas, a species in which males are polygynous but females mate monogamously so that "sperm competition" within the female reproductive tract is absent. (Wilson, M., Daly, M. (1992) The man who mistook his wife for a chattel: The Adapted Mind; (Barkow, J.H. & Cosmides, L. & Tooby, J. eds.), Oxford Univ. Press, New York. p. 299)

"Thus, the human penis shows high species-specificity as an elaborated genital structure. Penis size also varies moderately across populations, being largest among African populations, smaller among European populations, and smallest among East Asian populations, but with substantial overlap (Rushton, 1987, 1988b, 1989b). Penises are highly age-specific, attaining their full resting size only after puberty, and are highly courtship-specific, attaining their full erect size only under sexually arousing conditions. Thus, penises show all the hallmarks of a morphological trait elaborated somehow through sexual selection." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 185)

"Let us consider one factor that may predispose a species to male investment, female choice: females may prefer to mate with males who will invest strongly in their offspring. Most of the major kinds of male parental investment have been shown to affect female choice or may easily do so. At one time this would have been a controversial statement, but it is now well established, as the following studies suggest." (Trivers, RL (1985) Social Evolution. Benjamen/Cummings: Menlow Park. p. 249)

"Adult autralopithecine males would have had stonger social bonds with adult females, especially but not exclusively with their mothers and sisters, than is true for living chimpanzees. There was an even longer and more intense association with the mother and with siblings than for ancestral and transititional populations. Further incorporation of adult males into group life was made possible by increased sociability and decreased disruptiveness of the males (related both to the longer period of maternal care and socialization and to the probable decrease in sexual dimorphism, particularly in canine height). This relatively relaxed incorporation of males into the group was perhaps also reinforced by male contributions to defense and meat acquisition and by male help in bringing raw materials for tool manufacture from some distance to the campsite." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 219)

It may be suggested that in some cases a double process of selection has been carried on; that the males have selected the more attractive females, and the latter the more attractive males. This process, however, though it might lead to the modification of both sexes, would not make the one sex different from the other, unless indeed their tastes for the beautiful differed; but this is a supposition too improbable to be worth considering in the case of any animal, excepting man." (Darwin, C. (1871) The Descent of Man . John Murray: London p. 233-4)

"As we will see, humans are unusual in that both males and females have highly sex-specific, sexually-elaborated traits. In most animal species, only one sex, usually the male, shows sex-specific elaborations. This unusual human morphological pattern suggests that hominids underwent a pattern of mutual sexual selection with both males and females exercising selective mate choice with respect to somewhat different criteria." Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 156)

"He [Darwin] was prevented from harvesting all the fruits of his fertile imagination because he did not follow through with the logic of this own argument - to discover how female choice influenced the origin of the hominids; that is, to show how sexual selection was important at the very onset of human evolution. Because of an unfortunate blind spot engendered by his own cultural backround, Darwin was unable to explicate the necessary interrelationships and carry his own work on to its more logical conclusion." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 167)

“All combinations of male tactics from rape (Shields and Shields 1983, Thornhill and Thornhill 1983) to high investment (Trivers 1972) and the environmental and social circumstances that occasion their expression have recieved analysis in the literature. As Hrdy (1981) observed: “The sociobiological literature stresses the travails of males--their quest for different females, the burdens of intrasexual competition, the entire biological infrastructure for the double standard. No doubt this perspective has led to insights concerning male sexuality. But it has also effectively blocked progress toward understanding female sexuality--defined here as the readiness of a female to engage in sexual activity.” (Robert L. Smith (1984) Human Sperm Competition. in Sperm Competition and the Evolution of Animal Mating Systems pp. 602)

"Or should be perhaps compare the whale's brain to the peacock's tail, a scintilating mental display organ for the purpose of attracting a mate and enhancing the pleasures of courtship: the whale who provides the most stimulating entertainment having the best choice of mates?" (Lovelock, J (1979) Gaia, A New Look at Life on Earth. Oxford Univ. Press: Oxford. p. 141"

"Sexual selection requires (and provides a potential explanation for) a sexual dimorphism. For human cerebral function the most striking sex difference is in laterality (Bear et al, 1986) - men have a greater mean cerebral asymmetry than women (as noted by Crichton-Browne; see McGlone, 1980). This difference may account for the small but consistent differences that have been observed in the pattern of distribution of intellectual abilities - there is a mean difference for verbal fluency in favour of women and for spatial ability in favour of men (McGlone, 1980). The most striking sex difference if psychosis is earlier onset in men (Hafner et al, 1993; Lewine, 1991). Could the sex differences in cerebral organization (greater asymmetry and spatial ability in men; less asymmetry and greater verbal fluency in women) and the age of onset of psychosis be related? The following hypothesis (Crow, 1993a,b) (components of which are derived from earlier formulations as indicated in Table 3) relates them through Darwin's mechanism of sexual selection." (Crow TJ (1995) A Darwinian approach to the origins of psychosis. Br J Psychiatry 167(1):21)

"The evolution of modern Homo sapiens over the past 100,000 years has been marked by a trend toward increasingly craniofacial neoteny, including reduced prognathism, increased brachycephaly, and general gracilization in a number of populations. (Weidenreich 1945, Newman 1962, Brace and Mahler 1971, Frayer 1981). Biological anthropologists have generally invoked natural selection for ecological adaptation of nonadaptive forces such as pleiotropy or biased mutation to explain these trends. The analysis in this paper suggests that sexual selection may also be involved." (Jones, Doug (1995) Sexual selection, physical attractiveness, and facial neoteny: cross-cultural evidence and implications. Current Anthropology 36 (5): pp. 735)

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