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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 Library of Excerpts

Hominid Evolution: Heterochronic Patterns


"The existence of mammary ridges on the embryo concording with ancient synapsids suggests that those ancient animals also had nutrient-supplying ridges on their bodies for which there is no paleontological evidence. On the human embryo, the mammary ridges gradually coalesce and finally resolve into discrete nipples on day 58. This event concords almost exactly with the lowermost Triassic, where the fossils of Cynognathus are found. Discrete mammary glands and a fused secondary palate in the embryo coincide with a fused secondary palate in the fossil record." (Swan, Lawrence W. (1990) The concordance of ontogeny with phylogeny. Bioscience 40: 380)

"Bianki concluded that "in animals the parallel processor of information processing is localized in the right hemisphere and the sequential processor in the left one...The spatial processor, (and) the parallel one, is located in the right hemisphere and the temporel processor, like the sequential one, in the left." "(Ornstein, R. (1997) The Right Mind. Harcourt Brace & Co: San Diego p. 23)

"Writing in 1890, Gabriel de Mortillet suggested that left handedness may have been about twice as prevalent as right handedness in neolithic (late Stone Age) times. His excavations in France and Switzerland yielded 197 stone scrapers adapted to the left hand, 105 adapted to the right hand, and 52 usable by either." (Corballis and Beale 1983: 95-6, The Ambivalent Mind)

"First, and most obvious, standing up on the hind legs allowed our ancestors to use their forelimbs in a new way. As long as an animal moves on all fours, it needs to be able to move in either direction with any limb, to be equally responsive to a sudden danger or an attack on either side. So almost all animals evolved two-sided symmetry in overall body shape and in their sensory and motor systems. Movements that were too strongly one-sided might produce dangerous responses in an emergency. But when the first australophithecine or perhaps their immediate ancestors (Ramidus) first stood up, the front limbs no longer directly had anything to do with where the animal is headed. So the human forelimbs became specialized hands and the brain's control of them expanded. The extreme of this is when all the limbs get free of the ground, then cerebral specialization can develop readily. This is why birds' brains are more symmetrical than other animals." (Ornstein, R. (1997) The Right Mind. Harcourt Brace & Co: San Diego p. 30)

"As mental capacities expanded, and evolving hominids were taking in, processing, interpreting, acting on more and more information gleaned from the natural and social environments, some means of selectively organizing and transmitting such information became necessary. Similarly, as hominids became more and more enchanted and troubled by memories of dream images, a need for symbols to define and order meaning emerged. Such symbols then could be used to communicate not only remembrances of dreams but to share memories of what was seen or done during the day with others after returning to camp." (Tanner N, Zihlman A (1976) Discussion Paper: The Evolution of Human Communication: What can Primates Tell Us? in Origins and evolution of language and speech. Harnad, S., Steklis, H., & Lancaster, J. (eds.) New York Academy of Sciences: New York pp. 475)


"And, for the premodern revivalists, the cure is somehow to recontact and resurrect our acorness, We must get back to a state prior to the "dissociation." But because these theorists tend to confuse differentiation and dissociation, they confuse dignity and the disaster, they confuse forward and backward. They would have us heal the dissociations and modernity, which is well and good; but because they do not distinguish between differentiation and dissociation, they keep looking for a previous period in history where there were no differentiations at all; this forces them to look further and further back into prehistory, searching for that state of perfect acorness prior to any nasty divisions. They inevitably end up at one of the earliest stages of human evolution--foraging or horticulture--and this simple state of fusion and indissociation is eulogized as being very close to a state of perfect harmony among mind, body, and nature--when in fact those systems were not integrated, they were simply not yet clearly differentiated in the first place." (Wilber, Ken (1998) The Marriage of Sense and Soul. Random House, New York p. 54)

“Geschwind and Levitsky (1967) reported that in 100 postmortems, a larger planum was found on the left side in 65 brains, on the right side in 11 and in the remaining 24 the two sides were about equal. Galaburda et al. (1987) looked at the actual sizes of the plana on each side in this same series. They found that in symmetrical brains, both plana were large, while in asymmetrical ones (the typical pattern) the size of the planum on the right side was reduced, while the left stayed about the same. Thus, the typical pattern of asymmetry seems to be associated with a reduction on the right side, rather than expansion on the left; and symmetrical brains show no reduction on either side. Similarly, for the right and left hands, it looks as though bias to the right hand depends on loss of left hand skill, rather than increased skill on the right.” (Annett M (1991) Right hemisphere costs of right handedness in Vision and Visual Dyslexia, Stein JF (ed.) CRC Press, Boca Raton pp. 87)

"Feedback made this development circular. As neoteny progressed, it became still more necessary for the male to support his mate and the young; as the father became more important for the long-helpless young, there was more competition among females to secure and hold helpful mates, that is, to make herself attractive, which meant more neotenic. It also made the reproductive success of the male dependent not only on insemination but on seeing his children to maturity. If he became fonder of his children and his somewhat childlike mate, the family was complete."(Wesson, Robert (1991) Beyond Natural Selection. MIT Press: Cambridge p. 273)

"Brain tissue is metabolically expensive, but there is no significant correlation between relative basal metabolic rate and relative brain size in humans and other encephalized mammals. ...No matter what is selecting for relatively large brains in humans and other primates, they cannot be achieved without a shift to a high-quality diet unless there is a rise in the metabolic rate. Therefore the incorporation of increasingly greater amounts of animal products into the diet was essential in the evolution of the large human brain." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 199)

"In so far as there is differential expression of the gene in the two sexes it will be subject to sexual selection, i.e., the effects of different criteria, or timing, of mate choice in the two sexes. Such selective influences will determine the range of variation maintained separately in the populations of males and females. These in turn will exert their effects through actions on the rate and degree of lateralization. Thus the sex difference in the rate of maturation may be secondary to the fact that mate choice (for optimal features of the species characteristic of language) occurs at a later age in males than females (males are one to two years older than females at the time of marriage a difference that is consistent across cultures." (Crow TJ, Crow LR, Done DJ, Leask S (1998) Relative hand skill predicts academic ability: global deficits at the point of hemispheric indecision. Neuropsychologia : )

"One single gene disorder, fragile X, has recently been discovered that is X-linked, is found predominantly in males, and appears to have a specific association with autism. The clinical features are somewhat variable, but in its most severe form, the affected males are mentally retarded after puberty, have enlarged testicles. They tend to be hypotonic and to have somewhat long faces and large ears, but as children they do not appear particularly dysmorphic (Brondum-Nielsen, 1983). This syndrome of X-linked mental retardation was clinically recognized before the discovery of its association with fragile X and was known as the Martin-Bell syndrome (Martin & Bell, 1943)" (Folstein SE, Rutter ML (1988) Autism: Familial aggregation and genetic implications. J Autism and Developmental Disorders 18: pp. 16-17)

"During the Pleistocene, and probably before, a hominid species would have met the preconditions for the evolution of reciprocal altruism: long lifespan; low dispersal rate; life in small, mutually dependent, stable, social groups (Lee and DeVore, 1968; Campbell, 19660; and a long period of parental care. It is very likely that dominance relations were of the relaxed, less linear form characteristic of the living chimpanzee (Van Lawick-Goodall, 1968) and not of the more rigidly linear form characteristic of the baboon (Hall and DeVore, 1965). Aid in intraspecific combat, particularly by kin, almost certainly reduced the stability and linearity of the dominance order in early humans." (Trivers, R. (1971) The evolution of reciprocal altruism. Quarterly Review of Biology 46: pp. 45)

"This means that the average human has a brain that is 4.6 times the size expected for the average mammal and the average non-human primate anthropoid has a brain almost twice as large as that of the average mammal. The second factor is the metabolic cost of the brain. On the basis of in vivo determinations, the mass-specific metabolic rate of the brain is approximately 11.2 W.Kg-1 (watts per kilogram) (table 1, Aschoff, Gunther, and Kramer 1971). This is nine times higher than the average mass-specific metabolic rate of the human body as a whole (1.25 W.Kg-1)." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 200)

"For gatherers, the situation was different. Those women with the largest repertoire of communicable images of foods and their sources and secrets of preparation were unquestionably placed in a position of advantage. Language may well have arisen as a mysterious power possessed largely by women -- women who spent much more of their waking time together -- and, usually, talking -- than did men, women who in all societies are seen as group-minded, in contrast to the lone male image, which is the romanticized version of the alpha male of the primate group." (McKenna, T (1992) Food of the Gods. Bantom Books: New York p. 55)

“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 differentiation 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 parameter 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 suffer 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 fact, the mean BMR's of mature men and women straddle the values predicted by both primate and eutherian equations for mammals of comparable body mass (fig. 2). Consequently, there is no evidence of an increase in basal metabolism sufficient to account for the additional metabolic expenditure of the enlarged brain. Where does the energy come from to fuel the encephalized brain?" (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 201)

"Although the human heart and kidney's are both close to the size expected for a 65-kg primate, the mass of the splanchnic organs is approximately 900 g less than expected. Almost all of this shortfall is due to a reduction in the gastro-intestinal tract, the total mass of which is only about 60% of that expected for a similar-sized primate. Therefore, the increase in mass of the human brain appears to be balanced by an almost identical reduction in the size of the gastro-intestinal tract." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 204

"Obviously, it is impossible to determine the total daily energy expenditure--the field metabolic rate (FMR) --- of earlier hominids, but interferences about the likely levels of energy utilization can be made from measurements of modern humans and other living mammals." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 205

"This analysis implies that there has been a coevolution between brain size and gut size in humans and other primates. The logical conclusion is that no matter what is selecting for brain-size increase, one would expect a corresponding selection for reduction in the relative size of the gut. This would be essential in order to keep the total body BMR at the typical level. If it was necessary for a primate to have a large gut, that primate would also be expected to have a relatively small brain." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 205)

"If the hypothesis of coevolution is correct, what is essential for understanding how encephalized primates can afford large brains is identifying the factors that allow then to have relatively small guts. The gut is the only one of the expensive metabolic tissues that could vary in size sufficiently to offset the metabolic cost of the encephalized brain. The reason for this is that, although gut size is related to body size, its size and proportions are also strongly determined by diet...Gut size is associated with both bulk and the digestibility of food. ... There is also a close relationship between relative gut size and relative brain size (fig. 4). Animals with relatively large guts also have relatively small brains, while animals with relatively small guts have relatively large brains." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 206)

"Although all hominids are more encephalized than the majority of living primate genera, the australopithecines show an overall lower encephalization than members of the genus Homo. They are similar in degree of encephalization to Pan, Hylobates, and Saimiri, which suggests that they had a diet a least equal in quality to that of these primates." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 208)

"H. ergaster is the first known hominid to approximate modern human body proportions (Ruff and Walker1993). The inference is that it most probably also had a relatively smaller gut. ... For the second increase, the introduction of cooking may have been an important factor. Cooking is a technological way of externalising part of the digestive process. It not only reduces toxins in food but also increased its digestibility (Stahl 1984, Sussman 1987). This would be expected to make digestion a metabolically less expensive activity for modern humans than for non-human primates or earlier hominids. Cooking could also explain why modern humans are a bit more encephalized for their relative gut sizes than the non-human primates (see fig. 4)." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 210)

"The threefold increase in hominid brain size since the Pliocene is paralleled by a 3.2 times increase in brain size in equids (from 270 g in Pliohippus to 870 g in modern horse (Jerison 1973)) and does not seem exceptional. The uniqueness of hominid evolution rests in the lack of expected increase in body size." (Henneberg, M.(1995) response to ...Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 213)

"During sleep, metabolic rate falls to about 10% (Blaxter 1989). It also falls in other contexts, such as during starvation. It can differ between human populations by as much as 17% (Blaxter 1989: 144)." (Wrangham RW, Jones JH, Leighton M (1995) response to ...Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 216)

"As Falk has clearly stated, we view these factors [diet, gut size & encephalization], for the most part, as "prime releasers' which make available the not inconsiderable energy resources that are a necessary concomitant of encephalization." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 217)

"We suggest that the change in body proportions in H. ergaster in relation to the australopithecines may have marked a major shift to a higher-quality food and correspondingly smaller guts." (Aiello, Leslie C. (1995) Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution. Current Anthroplogy 36(2): pp. 219)

"The strontium:calcium ratio of the human samples is about 60% of the strontium:calcium ratio of the herbivorous mammal samples at the three sites (see Fig. 6). Based on the results of this analysis, nothing other than a constant proportion of meat versus vegetable material can be shown in the diets of humans throughout the time represented by these sites (70,000-35,000 years BP). It is possible that different foods were being collected even though there was no net change in the meat:vegetable proportions. The composition of the fauna, recovered from the three sites, however, suggests that there was no change in the kinds of fauna being exploited other than changing from one genus of large bodied herbivore to another (Garrod and Bate, 1937, Bouchud, 1974)." (Schoeninger, Margaret (1982) Diet and evolution of modern human form in the middle east. American Journal of Physical Anthropology 58(1): pp. 47)



"Between the time represented at Skhul and Qafzeh (30,000 - 35,000 BP) and the time represented at Kebara C (around 15,000 BP) there was a decrease in robustness but no change can be demonstrated in the average human diet." (Schoeninger, Margaret (1982) Diet and evolution of modern human form in the middle east. American Journal of Physical Anthropology 58(1): pp. 48)

"The distributions of strontium and stronum:calcium ratios from the two late phase pipaleolithic sites (Kebara B and el-Wad which date to around 10,000 years BP), compared with all the earlier sites, however, suggest that a major dietary change occurred between early and late phases of the Epipaleolithic. The strontium:calcium ratios of the human samples are over 90% that of the strontium:calcium ratios in their respective faunal samples (Fig. 6). The large increase in this ratio between the early Epipaleolithic level site (Kebara C) and the two late Epipaleolithic level sites (Kebara B and el-Wad) suggests that the major dietary shift occurred some 15,000 years after the major morphological shift had been completed. ... Both the results of the trace element analysis and the archeological record, therefore, indicate that the change in subsistence activities related to dietary components occurred long after the change in skeletal robustness from archaic to modern Homo sapiens. In fact, the shift toward greater dependence on plant products, occurred some 15,000 years after the first appearance of fully modern Homo sapiens." (Schoeninger, Margaret (1982) Diet and evolution of modern human form in the middle east. American Journal of Physical Anthropology 58(1): pp. 49)

"The hypothesis is proposed that these problems are related both to each other and to the speciation event that gave rise to modern Homo sapiens 137,000 or more years ago. A genetic change allowed the two hemispheres to develop with a degree of independence: the capacity for language (with a dominant focus in one hemisphere) evolved as a result of selection acting upon a dimension of variation generated by a single polymorphism plus a random component. Psychosis is the element of the variation associated with failure to establish dominance for language in one or other hemisphere (hemisphere indecision')" (Crow TJ (1996) Language and psychosis: common evolutionary origins. [received from author without publisher name on document] p. 105-109)


"And a group, rather than a single mated pair such as we find among birds, has probably always been the real functional unit of human society and, therefore, of human evolution. Several hunters in collaboration can do a better job of obtaining game than one and a far better job of protecting the headquarters and the youngsters than could one by herself." (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. 29)

"So if men did more of the hunting and scavenging whereas women did the bulk of the collecting of vegetables, women had essential jobs two million years ago. With time, these gender roles would select for men's knack for maps and mazes and other spatial skills, their aggressiveness, and their gross motor coordination. And as days turned into centuries, women's spatial memory for stationary objects, their verbal acuity, their facility for nurturing, their fine motor abilities, and their uncanny intuition would become firmly established as well." (Fisher, H. (1992) Anatomy of Love: The Mysteries of Mating, Marriage, and Why We Stray. Simon & Schuster, New York, 1992. pp. 203)

"Most important, Twiggy [hypothetical hominid] and her friends ate meat. And as I have maintained, hunting and scavenging are not logical pastimes for pregnant women or mothers with small children. So Twiggy probably let her lover collect the meat, the sinew and the marrow from dangerous beasts, while she gathered fruit, vegetables, seeds and small game with her female friends. In this way Twiggy made an enormous contribution to the evening meal. If so, she was economically powerful, as traditional !Kung women were and still are. The more sexually active and charismatic females in Twiggy's world were probably more powerful as well." (Fisher, H. (1992) Anatomy of Love: The Mysteries of Mating, Marriage, and Why We Stray. Simon & Schuster, New York, 1992. pp. 219)

"However, this discrepancy became understandable when it was realized that the newborn infant concords very well with 20 million years ago in the Miocene epoch, when our ancestors were apes of some sort. Newborn infants can often grasp and suspend themselves and even swing enough to suggest brachiation. Their hallux or big toe is often highly movable and the rest of their feet (showing a slope of their curled toes that is virtually transverse) are apelike. In an evolutionary sense, a newborn concords well with some ancestral Miocene ape. However, after nine months of a year, when the curve is found at the time of birth, a child approaches the evolutionary present. It starts to stand erect and practices with its lumbar curve before it walks upright. Its hallux assumes a forward position, and its starts to acquire the normal slope of human toes. The chin acquires a better-defined protuberance that expresses Homo sapiens as a species, and the jabberings of an infant transform into human speech." (Swan, Lawrence W. (1990) The concordance of ontogeny with phylogeny. Bioscience 40: 383)

"It is satisfying to consider embryos and adults as merely different parts of the slope of a curve subject to natural selection. If biologists cannot agree to Haeckel's concept, "ontogeny recapitulates phylogeny," there may be room for a less ringing slogan, "ontogeny concords with phylogeny."" (Swan, Lawrence W. (1990) The concordance of ontogeny with phylogeny. Bioscience 40: 384)

"Male afarensis are much larger than females. One thing we know with confidence form other primates is that differences in body size between the sexes indicates a polygynous mating system (Clutton-Brock and Harvey 1976). Males evolve larger because big bodies help them in male-male competition. Male and female members of mongamous primate systems, in which there is little male-male competition, tend to be about the same size. Thus Lucy was probably not living in a monogamous social system. She may have been in a harem situation, but it's equally possible that she had access to several males and that they had access to her." (Small, Meredith F. (1993) Female choices: Sexual behavior of female primates. Cornell Univ. Press, Ithaca, 1993 pp. 190)

"Fully modern human form more gracile than the antecedent archaic modern form was evident by 30,000 years ago. One hypothesis to explain this decrease in skeletal robustness is that change occurred in human diet and that this change was associated with a decrease in activity levels required in both individual and group behavior. It is possible to study dietary change directly using trace element analysis of strontium levels in bone. The amount of strontium in bone reflects the amount of strontium in diet. Since plants contain higher levels of strontium than do animal soft tissues, the level of bone strontium will differ between individuals according to the proportion of plant and animal products in their diets. In this study the ratio of strontium:calcium in human bone to strontium:calcium in faunal bone is compared for samples of archaic modern humans (from Mugharet et Tabun, Mugharet es-Skhul, and Jebel Qafzeh) and fully modern humans from Mugharet el-Kebara and Mugharet el-Wad) from Israel. The use of a ratio controls for potentially unequal strontium levels in soils at different sites and for different diagenetic histories between sites. The results of the analysis are internally reliable, reflecting bone strontium levels rather than technique error; therefore, they reflect diet. It appears that a change occurred in the amount of animal protein in the diet of humans but that this change occurred almost 20,000 years after the first appearance of skeletally modern humans. These results refute the hypothesis that the morphological transformation to modern human form occurred as a result of behavioral changes involved in obtaining previously unused foods. If any decrease in human activity level occurred between archaic modern and fully modern humans, this decrease probably was due to alterations in the means of procuring or processing the same kinds of foods that had been utilized earlier in time." (Schoeninger, Margaret (1982) Diet and evolution of modern human form in the middle east. American Journal of Physical Anthropology 58(1): pp. 37)

"If it is assumed that the last common ancestor of apes and humans had a diet similar to that of a modern ape, and that the earliest members of our species (Homo sapiens sapiens) consumed a diet whose composition fell within the range encompassed by modern hunter-gatherers, then it appears that hominid evolution was characterized by increasing diet quality. The distinctiveness of the human diet relative to other primates is likely associated with important metabolic differences. One possibility is that the high caloric density of our diet is reflective of elevated resting metabolic requirements." (Leonard, William R. (1994) Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and metabolism. American Journal of Human Biology 6(1): pp. 79)

"Dietary patterns strongly influence metabolic requirements in mammalian species (McNab, 1978, 1986; Kurland and Pearson, 1986; Nagy, 1987). McNab (1986) found that mammals consuming high quality food items, such as, vertebrates, seeds, or nuts, tended to have high resting metabolic rates (RMR), while those consuming poor quality foods, e.g., leaves and woody plants, tended to be hypometabolic. If such a pattern holds for primates, it should be expected tht metabolic rates will vary according to relative diet quality." (Leonard, William R. (1994) Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and metabolism. American Journal of Human Biology 6(1): pp. 80)

"These results imply that changes in diet quality during hominid evolution were linked with the evolution of brain size. The shift to a more calorically dense diet was probably needed in order to substantially increase the amount of metabolic energy being used by the hominid brain. Thus, while nutritional factors alone are not sufficient to explain the evolution of our large brains, it seems clear that certain dietary changes were necessary for substantial brain evolution to take place. ... It is intriguing that the clear departure from the general primate brain-metabolism regression occurs with the emergence of species of our own genus, H. habilis and H. erectus, since this is a time when other important anatomical and behavioral changes appear. Specifically, both archeological and morphological evidence indicate that these early members of the genus Homo incorporated greater amounts of animal material in their diet than the australopithecines (Bunn, 1981; Wolpoff, 1980). With early Homo there is the first clear evidence of home bases, implying that resources were collected and brought back to a central location where they were shared. (Potts, 1988). Hence, it is likely that what supported the rapid expansion of brain size in Homo habilis and Homo erectus were both the higher quality and greater stability of the diet." (Leonard, William R. (1994) Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and metabolism. American Journal of Human Biology 6(1): pp. 83-4)

"Contemporary human foraging groups obtain at least 30% of their dietary energy from animals foods, compared to 5-7% in chimpanzees. Adaptation to this calorically dense, easy to digest diet is evident in our gut morphology, as humans have a relatively reduced digestive tract in comparison to most other primates (Sussman, 1987; Chivers and Hladik, 1980; Milton, 1987). This distinct diet appears to be linked to the high metabolic costs of the human brain. In general, primate brain size varies as a direct (linear) function of body metabolism. This means that the proportion of metabolic energy spent on the brain is relatively constant across primates of all size (about 8-9% of RMR). Species spending a larger proportion of RMR on their brain have a higher quality diet than expected for their body size. Conversely, small brains relative to metabolic turnover are associated with poor quality diets. Humans represent the positive extreme, having both a very high quality diet and a brain that accounts for 20-25% of resting metabolic energy. Other researchers have previously noted the apparent link between metabolic rate and brain size. (Armstrong, 2985; Mink et al., 1981; Martin, 1989, 1990). In particular, Martin (1989) has argued tht this relationship reflects the association between brain growth and maternal metabolism. This hypothesis posits that since the majority of brain growth in humans and other primates occurs prenatally and early in the postnatal period, it is maternal metabolic output (through pregnancy and lactation) that largely determines achieved adult brain size. If this hypothesis is correct, the results of the present study would imply that improvement in the stability and quality of maternal nutrition (to support the high metabolic demands of pregnancy and lactation) was a consequence of the selection for larger brain size in hominid evolution." (Leonard, William R. (1994) Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and metabolism. American Journal of Human Biology 6(1): pp. 85)

"The progressive slowing of life phases can in turn be accounted for by an increasingly K-type demographic strategy (45). With each step in the scala naturae, populations devote a greater proportion of their reproductive energy to subadult care, with increased investment in the survival of fewer offspring." (Lovejoy, C.O. (1981) The o rigin of man. Science 211: pp. 344)

"In their discussion of A. afarensis, Johanson and White (17,85) note that although this species shows "marked body size dimorphism, the metric and morphological dimorphism of the canine teeth is not as pronounced as in other extant, ground-dwelling primates. This implies a functional pattern different from that seen in other primates and may have significant behavioral implications." (6). The reduction and effective loss of canine dimorphism in early hominids therefore serves as primary evidence in favor of the proposed behavioral model (86)." (Lovejoy, C.O. (1981) The o rigin of man. Science 211: pp. 346)

"Whatever the actual sequence of events, whether as posed above or by some alternative order, such additional investment would improve survivorship and favor a mating structure that intensified energy apportionment to the male's biological offspring." (Lovejoy, C.O. (1981) The o rigin of man. Science 211: pp. 346)

"As Reynolds (94) stressed, intense social behavior would seem the most likely single cause of the origin of human intelligence if one origin must be isolated. Tools are used to manipulate the environment and are thus a vehicle of intelligence, not necessarily a cause. Chimpanzees occasionally use tools (a behavior that has fascinated many early hominid theorists), but tools are not critical to their survival. Primates, which are the most intelligent mammals, have achieved evolutionary success primarily by their social and reproductive behavior, which is their most developed ordinal character. It seems reasonable therefore to propose that a further elaboration of this adaptive strategy is the most likely "cause" of early hominid success and the further development of intelligence." (Lovejoy, C.O. (1981) The o rigin of man. Science 211: pp. 347)

"If the model is correct, the conventional concept that material culture is pivotal to the differentiation and origin of the primary characters of the Hominidae is probably incorrect. Rather, both advanced material culture and the Pleistocene acceleration in brain development are sequelae to an already established hominid character system, which included intensified parenting and social relationships, monogamous pair bonding, specialized sexual-reproductive behavior, and bipedality. It implies that the nuclear family and human sexual behavior may have their ultimate origin long before the dawn of the Pleistocene." (Lovejoy, C.O. (1981) The o rigin of man. Science 211: pp. 348)

"If it is assumed that the last common ancestor of apes and humans had a diet similar to that of a modern ape, and that the earliest members of our species (Homo sapiens sapiens) consumed a diet whose composition fell within the range encompassed by modern hunter-gatherers, then it appears that hominid evolution was characterized by increasing diet quality. The distinctiveness of the human diet relative to other primates is likely associated with important metabolic differences. One possibility is that the high caloric density of our diet is reflective of elevated resting metabolic requirements. Indeed, the work of McNab (1986) and Nagy (1987) indicates that greater diet quality is associated with higher resting and total metabolic rates among mammalian species. An alternative hypothesis is that the high metabolic costs of our large brain necessitate an energy-rich diet (Martin, 1989; Leonard and Robertson, 1992). Each of these possibilities is examined subsequently. ... Dietary patterns strongly influence metabolic requirements in mammalian species (McNab, 1978, 1986; Kurland and Pearson, 1986; Nagy, 1987). McNab (1986) found that mammals consuming high quality food items, such as, vertebrates, seeds, or nuts, tended to have high resting metabolic rates (RMR), while those consuming poor quality foods, e.g., leaves and woody plants, tended to be hypometabolic. If such a pattern holds for primates, it should be expected that metabolic rates will vary according to relative diet quality. " (Jolly, Clifford J. (1963) A suggested case of evolution by sexual selection in primates. Man (London) 63: 79-80)

"These results imply that changes in diet quality during hominid evolution were linked with the evolution of brain size. The shift to a more calorically dense diet was probably needed in order to substantially increase the amount of metabolic energy being used by the hominid brain. Thus, while nutritional factors alone are not sufficient to explain the evolution of our large brains, it seems clear that certain dietary changes were necessary for substantial brain evolution to take place. ... It is intriging that the clear departure from the general primate brain-metabolism regression occurs with the emergence of species of our own genus, H. habilis and H. erectus, since this is a time when other important anatomical and behavioral changes appear. Specifically, both the archaelogical and morphological evidence indicate that these early members of the genus Homo incorporated greater amounts of animal material in their diet than the australopithecines (Bunn, 1981; Wolpoff, 1980). With early Homo there is the first clear evidence of home bases, implying that resources were collected and brought back to a central location where they were shared (Potts, 1988). Hence, it is likely that what supported the rapid expansion of brain size in Homo habilis and Homo erectus were both the higher quality and greater stability of the diet. (Jolly, Clifford J. (1963) A suggested case of evolution by sexual selection in primates. Man (London) 63: 83-84)

"Contemporary human foraging groups obtain at least 30% of their dietary energy from animals foods, compared to 5-7% in chimpanzees. Adaptation to this calorically dense, easy to digest diet is evident in our gut morphology, as humans have a relatively reduced digestive tract in comparison to most other primates (Sussman, 1987; Chivers and Hladik, 1980; Milton, 1987). This distinct diet appears to be linked to the high metabolic costs of the human brain. In general, primate brain size varies as a direct (linear) function of body metabolism. This means that the proportion of metabolic energy spent on the brain is relatively constant across primates of all size (about 8-9% of RMR). Species spending a larger proportion of RMR on their brain have a higher quality diet than expected for their body size. Conversely, small brains relative to metabolic turnover are associated with poor quality diets. Humans represent the positive extreme, having both a very high quality diet and a brain that accounts for 20-25% of resting metabolic energy. Other researchers have previously noted the apparent link between metabolic rate and brain size. (Armstrong, 1985; Mink et al., 1981; Martin, 1989, 1990). In particular, Martin (1989) has argued that this relationship reflects the association between brain growth and maternal metabolism. This hypothesis posits that since the majority of brain growth in humans and other primates occurs prenatally and early in the postnatal period, it is maternal metabolic output (through pregnancy and lactation) that largely determines achieved adult brain size. If this hypothesis is correct, the results of the present study would imply that improvement in the stability and quality of maternal nutrition (to support the high metabolic demands of pregnancy and lactation) was a consequence of the selection for larger brain size in hominid evolution." (Jolly, Clifford J. (1963) A suggested case of evolution by sexual selection in primates. Man (London) 63: 84-5)

"In our view, the three australopithecines are, in a number of features, scaled variants of the "same" animal. In these characters, A.africanus is no more "advanced" than the larger, more robust forms. The one early hominid to show a significant departure from this adaptive pattern toward later hominids ---- cranially, dentally, and postcranially --- is H. habilis from East Africa. The australopithecines, one of which was probably a precursor of the Homo lineage, were apparently a successful group of basicly vegetarian hominids, more advanced behaviourally than apes (Mann, 1968), but not hunter-gatherers." (Pilbeam, D. & Gould, S.J. (1974) Size and scaling in human evolution. Science 186: pp. 900)

"Rates of evolutionary change in different early hominid groups during the same length of secular time, exhibited principally as differences in the rate of neotenous mutations --- among other factors --- are quite sufficient, it is suggested, to explain such apparent anachronisms as neanthropic types of man in the Middle or even Early Pleistocene and a palanthropic type of man in the Upper Pleistocene --- always, providing, of course, that we are also finally able to understand the adaptive value of these neotenous changes." (Montagu, Ashley (1955) Time, morphology, and neoteny in the evolution of man. American Anthropologist 57: pp. 27)

"The hypothesis advanced in this paper suggests that commencing with a single hominid ancestral population, which has subsequently separated into several geographically isolated populations, that in addition to such factors as mutation, natural selection, isolation, drift, and the like, neotenous mutations have played an important role in adding to the quanta of morphological difference among such populations. Neotenous mutations occurring at a more rapid rate in some early populations than in others would, at least in part, be responsible for the development of morphologically modernlike types of man at a period contemporary with the flourishing of such types of Pithecanthropus, Heidelerg, and Solo man. The hypothesis suggests that in the latter types neotenous mutations occurred comparatively infrequently." (Montagu, Ashley (1955) Time, morphology, and neoteny in the evolution of man. American Anthropologist 57: pp. 27)

"Lieberman (1984) argued that even the Neanderthals, who lived as recently as 35,000 years ago, would have been incapable of modern speech, on the grounds that they retained a vocal tract that simply could not have produced the requisite range of sounds. It is not unlikely that they communicated vocally but without the speed and flexibility that characterize our speech. Lieberman also noted, however, that fossil skulls of H. sapiens sapiens found at Broken Hill in Zambia, and dating from about 150,000 years B.P., do appear to have possessed the angled vocal tract necessary for modern speech." (Corballis, M.C. (1989) Laterality and human evolution. Psychological Review 96 (3): pp. 498)

"Clutton-Brock and Harvey (1980) showed that primate relative brain size decreases as the proportion of leaves in the diet increases. They suggested that a larger memory is needed to exploit fruits, which are relatively more scattered and patchy in occurrence than leaves. A similar pattern has recently been found in myomorph rodents (Mann et al., 1988). Folivorous groups average only about two-thirds the brain size of granivorous, insectivorous, or generalist groups of the same body weight. Hence, we may infer that nonfolivory played a role in our ancestors reaching the threshold. An important additional factor has been extensively discussed by Gibson (1986 and references therein) who has shown that primates regularly eating foods that need to be extracted from the environment have relatively larger brains. Such "extractive foods" include such diverse diets as nut-meat, pod seeds, termites, snails, and many others. While they are more trouble to extract, they are generally higher in nutrition and more available throughout the year compared to more readily eaten foods such as berries or leaves. Omnivorous diets of extractive foods lead to the largest relative brain sizes of all, as opposed to those primates which specialize on just one of a few types. Hence, it may be that dietary habits of extractive omnivory and nonfolivory played a major role in the development of brains large enough to reach the threshold." (McKinney, M.L. & McNamara, K.J (1990) Heterochrony: The Evolution of Ontegeny: Plenum Press, New York p. 324)

"Overall, females apparently were choosing males who were sociable, cooperative, willing to share, and protective. In general, then, sexual intercourse would not be disruptive of either ongoing group interaction or organizational flexibility. Mothers obtained plant food from their own efforts, protein from a variety of sources (insects, plant protein, and some meat form their own efforts, and additional meat from males); had their own tools for protection; and had durable social bonds with sons, daughters, brothers, and sisters who shared the food quest and assisted in protective functions. Thus permanent mates to provide food and protection would be neither necessary nor particularly advantageous. Sexual preference was, however, getting easier to communicate, and it is likely that many australopithecines did have preferred sex partners." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 210)

"Adult australopithecine males would have had stronger 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 transitional 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 defence 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)

"Although others have mentioned that early hominids probably gathered much of their food, until quite recently the prevailing idea underlying reconstructions of social behavior has been that Austalopithecus was primarily a hunter. There are, however, considerable data that are anomalous from a hunting perspective. For their small size, all australopithecines --- even the early basal hominids and the so-called gracile line --- had powerful chewing and grinding capacities. This kind of chewing apparatus is best understood as an adaptation to a diet including a high proportion of tough, uncooked plant food. Further, given their small size and still very simple technology, it is improbable that they pursued, captured, and killed large dangerous animals with tools. The data on size, tools, and teeth do not fit a hunting model but make a great deal of sense when viewed within a gathering context." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 193)

"In function (as indicated by height and absolute breadth), australopithecine canine teeth were quite similar for males and females. In subsequent hominids, Homo erectus and Homo sapiens, breadth decreases a bit further and bimodality disappears. Given this trend, the bimodal distribution for canine breadth in the australopithecines strongly suggests that the ancestral population was one in which canines were both functionally and anatomically dimorphic (with differences in both length and breadth), as Darwin (1871) hypothesized long ago." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 200)

"Second, Holloway (1967) hypothesized that changing social and mating patterns led to less intraspecific fighting among males and between males and females. Thus, as female choice increased (correlated with increased maternal investment and with the increased cortical control of sexual behavior consequent to the loss of estrus), the more social (and less aggressive and disruptive) males may well have been more frequently selected as sexual partners. This change is mating patterns would have affected the whole group by increasing sociability among males and between males and females." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 202)

"The evidence is also clear regarding female chimpanzees' significantly more frequent preparation and use of tools in food getting (albeit, in the case of chimpanzees, for insect gathering). Male chimpanzees simply do not use tools as often to obtain food, a fact consistent with the lesser nutritional stress on males. Further, there is not question but what mother chimpanzees share food with offspring. That tool-using, plant-gathering early hominid mothers would do likewise is probable. Also of interest are data on sexual dimorphism. Several remains at Laetoli and Hadar exhibit notable size differences---for example, the footprints at Laetoli and the upper jaws of AL200 and AL199 at Hadar. The differences in size can be interpreted as due to sexual dimorphism (Johanson and White, 1979). These size differences appear greater than those between sexes for humans today. However, the canine teeth do not appear to exhibit as pronounced dimorphism as among most living primates (Johanson and White, 1979). Quite possibly, then, A. afarensis had already undergone some reduction of sexual dimorphism, and its descendants were to undergo even more. This is consistent with the selective process hypothesized in Chapter 7: The gathering innovation led to increased maternal investment, which, in turn, was associated with preferential female sexual selection of males who, among other things, appeared less physically frightening or threatening to the females." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 190)

"Apes and humans share relatively complex Pb proteins and the PPb protein. All the apes are predominantly frugivorous-folivorous, whereas humans are omnivorous. What this means is that certain aspects of the diet did not change sufficiently in the process of becoming human for there to be strong selection for a change in salivary proteins from that of the apelike ancestors. Early humans shared with the apes saliva proteins useful in a diet having a great deal of plant carbohydrate and/or texture. This model suggests that the foods gathered by the early hominids had both." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 188)

"Although some food and protection were supplied by males, sexual partners were only occasionally and irregularly involved; brothers and sons who frequently associated with mothers and sisters probably were the males who most regularly contributed animal protein and protection." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 163)

"The more intelligent transitional female (remember, it is her offspring who will be most likely to survive) could use her intelligence to select males for copulation. In other words, increases in intelligence and a richer, more sophisticated communicatory repertoire mean the mating system itself could become more complex. I hypothesize that the mating system was changing so as regularly to include female discrimination and choice of sex partners in terms of a number of characteristics. Females probably had sex more frequently with those males who were around often, playing with offspring, helping in protection, occasionally sharing meat and foraged plants, and who were generally friendly. With females choosing the less disruptive males, there also would be less likelihood that males having sex with mothers might accidentally injure offspring. To the extent that the ability to learn to be more sociable has been enhanced by genetic changes that have augmented our human potential --- and this is a subject about which little is known --- sexual selection in the hominid divergence also could have increased the capacity of males for relaxed social interaction. ... What may have been selected for among the transitional hominid males was the capacity to be extremely social but yet sufficiently aggressive when required and an ability to make fine discriminations as to situational necessity. Thus, the males of the transitional population would come to more closely resemble the females than had the males of the ancestral population. ... Much of the selection pressure engendered by female choice of sexual partners was directed toward male social and communicatory behavior, reinforcing the potential and capacity for sociability, social learning, and intelligence." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 164-5)

"Heightened maternal investment resulted, in turn, in increased sexual selection by females. Natural and sexual selection reinforced each other during the transition. Selective pressures were intense, and evolutionary change may well have been extraordinarily rapid." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 167)

"The measure of natural selection is reproductive success (Dobzhansky, 1970). The crux of the matter is how many offspring survive for any given female or male, rather than the number of copulations or number of infants born per se. Transitional hominid fathers, like the ancestral population before them, would not know their young and so could not effect the specific survival chances of their own progeny as differentiated from other young of the community." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 161)

"Furthermore, the extent and kinds of tool use exhibited by chimpanzees vary geographically. These regional variations in tool use partially accord with environmental exigencies. Partly, however, there are regional stylistic differences (McGrew et al., 1979). It has been suggested that perhaps it is "those traditions which are practiced mainly by migrant females (e.g., probing with tools for termites) that are...most likely to disseminate throughout a regional population" (Teleki, in press: 186). (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 75)

"McGrew (1979) reports that a female chimpanzee may obtain as much as 20 grams of ants in a typical session of ant dipping. From preliminary observations, females engage in these insect collecting activities with tools for longer periods and more often than do males (Nishida, 1973; McGrew, 1979)." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 73)

"Different prehuman species suggest different levels of sperm competition. Judging from its teeth, Australopithecus africanus was certainly a vegetarian. Like gorillas, the vegetarian australopithecines showed a bigger difference in body size between sexes than men and women do today, suggesting that they were sperm-competition avoiders. Although no one, of course, knows for sure, Robert Smith speculates that physically imposing males bossed relatively sexually faithful females in australopithecine harems. These ancestors would have been very sexist, but the males, violently intolerant of promiscuity, would not have developed large genitals. This sultanlike breeding behavior could well have undergone radical change with the evolution of Homo habilis, "handy man": Smith postulates that subordinate habilis males, scavenging meat and offering pieces of it in exchange for sex, upset the earlier breeding system. The cooperative hunting groups that began with Homo erectus --- our most recent evolutionary predecessor --- ushered in relatively high levels of sperm competition. Homo erectus males were not much larger than Homo erectus females. Homo erectus was a communal species who not only gathered edible plants but hunted mammoths and used fire. Eating and sleeping together in groups --- the sort of cooperative groups needed to hunt --- may have made them far more social, more talkative, and better barterers than their sexually dimorphic australopithecine ancestors. And more promiscuous. It was with Homo erectus, Smith suggests, that people developed their relatively large male genitals." (Margulis, L & Sagan, D. (1991) Mystery Dance, On the Evolution of Human Sexuality: Summit Books, New York pp. 51)

"Forest-dwelling apes efficiently conserve their water reserves, which they obtain primarily from fruit and vegetation, such that they need only rarely to visit predator-frequented watering holes. By contrast, humans active in hot desert can loose up to 28 liters of water and up to 10% of bodily salt reserves per day (Morgan, 1982). This incredible profligacy with water a salt suggests that early hominids must have enjoyed no shortage of either: they probably dwelled fairly close to fresh and salt water when not foraging. Rivers and lakes would have provided not only drinking water, but also allowed body-washing and food-washing, offered fish, aquatic crustaceans, and shellfish for eating, and, because the thermal conductivity of water is much higher than that of air, quick swims would have allowed for efficient cooling-off after a long, hot days of foraging. Note that these conditions would make the aquatic ape hypothesis (Hardy, 1960; Morgan, 1982) a bit more plausible..." Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 164)

"Since these chimpanzee species diverged only around 1.5 million years ago, the speed with which differences in sexual behavior can evolve under mate choice is clearly demonstrated." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 220)

"Many people assume that the opportunities for selective mate choice, particularly female choice, would have been severely limited under ancestral conditions, due to the supposed prevalence of arranged marriages, the exchange of women as chattel between families and tribes, the influence of cultural rules concerning incest, outbreeding, marriage, monogamy and adultery, the prevalence of within-class marriages in complex hierarchical societies, and the generally low status of women under 'patriarchy'. But there is strong archaelogical and anthropological evidence that many of these factors arose within the last 10,000 years (Fisher, 1992), and would not have restricted individual mate choice opportunities before that time. The economic and geographic demands of agriculture distorted human mate choice patterns, because agriculture requires long-term investment in preparing and maintaining a plot of land, and thereby reduces the physical and social mobility that underlay the free choice of sexual mates in hunter-gatherer tribes. Even a century ago, Westermark (1894) recognized that in pre-agricultural tribal societies, females exercised considerable powers of mate choice. With the rise of post-agricultural and post-industrial society, we are seeing a return to more 'natural' ancestral patterns, including more sexual experimentation in adolescence, higher rates of adolescent pregnancy, divorce, and 'infidelity', more serial monogamy, more single mothers, higher rates of bisexuality, and do forth. These new patterns probably represent the Pleistocene norm, not 'social problems' due to modern atheistic decadence. And under these new conditions, we see a dizzying variety of relationships emerging and of mate choice criteria being exerted. Thus, the sexual freedom and social complexity enjoyed by young people in contemporary urban North America and Europe is probably much more representative of ancestral tribal conditions than the cloistered, oppressive patriarchy of medieval Europe or the lifelong monogamy of the mid-20th century industrial United States." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 237-8)

"Our lineage can be visualized as an enormous parallel computer program for generating and processing behavioral courtship innovations: a genetic algorithm that cycles through an effective population size somewhere between 10,000 and 1,000,000, over 100,000 generations. At the beginning of the metaphorical computer run 1.8 mya, our ancestors had small brains, slow tongues, dull minds, and plain bodies; at the end of the run, 200,000 years ago, they had huge brains, quick tongues, creative minds, and ornamentally shaped bodies. But the computer analogy breaks down at the data/program dichotomy, because our ancestors were as once the program selecting among alternatives, and the data being selected among. The preferences and the traits co-evolved and self-organized." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 251)

"Studies of contemporary human hunter-gathers and other anthropoid apes suggest that females are generally capable of feeding and taking care of themselves and their children (Linton, 1971). Indeed, among many hunter-gatherer tribes, the men need the women more than vise-versa. It may be more accurate to think of male provisioning as a helpful if unreliable supplement on top of an already self-sufficient women-and-children foraging system, rather than as a desparately-needed stopgap that makes up for a pre-existing deficit of food or protection (Tanner, 1981). However, the nature of evolutionary fitness tends to make helpful supplements into relative necessities through the inexorable mechanism of Darwinian competition: if women who could elicit long-term male provisioning stayed healthier and had healthier children than women who couldn't, then there will be a strong selection in favor of traits that elicit traits such provisioning (Fisher, 1982, 1992; Lovejoy, 1980)." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 405)

"Bones of australopithecines, Australopithecus afarensis, were unearthed near Hadar, Ethiopia. The males of some of these ancestors were nearly twice as large as the females: on our evolutionary lineage, physical domination by males and feminine submission may be ancient phenomena." (Margulis, L & Sagan, D. (1991) Mystery Dance, On the Evolution of Human Sexuality: Summit Books, New York pp. 14)


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