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.
In chimpanzee society, a child would not know who his father was, the females having multiple partners. Early human culture would also have been characterized by the females choosing procreation partners at their own discretion, not an unlikely scenario considering that this is not an uncommon human aboriginal social constellation. A male often forms his allegiance with the next generation, not through his own progeny, but through his sister's. Jane Goodall informs us that in chimpanzee society the bonds of intimacy move through the mother (Goodall, 1990). It is siblings that form the closest bonds after the bond of mother with child. Lewis Henry Morgan (1877) made clear with his kinship studies that human societies up to historic times often operated with the males raising or mentoring their sister's sons, it being unclear to males who their own progeny were in societies with promiscuous social structures.
"It is very difficult to decide how far changed conditions, such as of climate, food, etc., have acted in a definite manner. There is reason to believe that in the course of time the effects have been greater than can be proved by clear evidence." Charles Darwin, The Origin of Species, 6th addition, 1872, p. 139. (referring to the inheritance of acquired characteristics)
Outside a lush environment, a chimpanzee or hominid female would have a difficult time bringing a child to maturity. There is powerful evidence that it was in periods of great climactic change that our ancestors made their greatest physical and societal evolution. Humanity's origin my have risen from a period when, during a time of food scarcity, the female hominids choose males inclined toward supplying the community (including his own unknown progeny) with food. In exchange for community membership, which included the right to be chosen as a procreation partner, the male hominid would make sure his sister's daughters and sons did not go hungry. Chimp behavior can suggest how the female hominid may have gone about choosing the father of her child, for it is with the premise that the early hominid female participates in choosing her copulation partner, just as in chimpanzee society, that this theory begins to fall into place.
The bonobo chimpanzee are a different species of ape than the chimps observed by Jane Goodall. In the bonobos the females are dominant to the males and the center of bonobo social structure (Kano, 1992; De Wall & Lanting, 1997). Sex is more characteristic of interpersonal relations in this species than any other mammal. The males live cooperatively, far less competitively than Goodall's chimps. The males are more attracted to the children. Like chimps, bonobos males do not know their paternity. The evolutionary relationship between the bonobo and the chimpanzee suggest a heterochronic trajectory (Shea, 1989; Blount, 1990; De Wall & Lanting, 1997) that will make, as we shall see, several pecularly human features make sense.
Briefly, we are proposing that for two million years, up to approximately 100,000 to 40,000 years ago, hominid evolution was driven by the criteria females used to select males for their procreation partners (Tanner, 1981) included males who were increasingly cooperative, social, and less aggressive (Young 1971). Males with these characteristics were more inclined to succeed in a promiscuous social environment (Morgan, 1877;Margulis & Sagan, 1991) and more likely to be responsive to the needs of women with infants and children helpless for long periods. These characteristics were evidenced by males with less testosterone (T) than the more aggressive males. And if, as we surmise, there is an inverse relationship between sperm production and testosterone production, then females selecting males low in T will be choosing males with larger testicles which produce more sperm making them a likely success in a promiscuous social structure.
By choosing males with low T, females are prolonging the developmental and maturation rates of their male progeny. In humans the relative levels of testosterone (and probably estrogen) in males and females is the primary hormonal intermediary between the eight environmental cues and relative rates of maturation. By prolonging growth, whether explained by heterochronic concepts of neoteny (Montagu, 1955, 1989; Gould, 1977) (prolonging child features into adulthood) or by hypermorphosis (Shea, 1989; McKinney and McNamara, 1990) (prolonging all developmental stages), one of the net results is increased brain and cranium size (Riska & Archley, 1985). Prolonging growth rates is achieved in humans by lowering T. Accelerating growth, in effect condensing developmental stages, is achieved by raising T.
We believe that there was a feedback loop effect speeding up the process of brain growth. This is similar to the process described by Wesson (1991), Miller (1994) and Brin (1995) and Crow, 1995) using Fisher's (1930) runaway theory of sexual selection. It is our hypothesis that song and dance created peculiarities of human consciousness leading to culture, as opposed to evidencing them. Song and dance---in combination with females choosing males with lower T---are primary forces responsible for the exponential rise in brain size in the last 2 million years.
We are hypothesizing several characteristics of pre-cultural, pre-language society that are not commonly part of modern society, characteristics which would have made the experience of early hominids profoundly different from our own. First, we are suggesting that there was a powerful sense of community grounded in mother, mother's brother, and siblings. Second, the brain of these early humans had no dominant hemisphere. These early people used both hemispheres for communication because their language was touch, was physical, was dance. Touch and feeling are represented in both hemispheres of the brain which is why a language of touch and feeling would be processed through both hemispheres. They lived in a single tense, non-differentiated world not unlike, in fact exactly like, our dreams and our unconscious.
Modern humans usually use a single hemisphere, most often the left, when engaging in spoken language. There is evidence that musicians use both hemispheres when processing music (Hassler, 1992). And even more intriguing, there is evidence that some ambidextrous individuals process speech through both hemispheres (Jaynes, 1976).
Though it is not uncommon in the anthropological literature that spoken language is hypothesized to have suddenly appeared with culture, the mechanism by which the vocal cords were prepared and ready for use at that time has been a riddle. Speech may not have evolved. It may have been invented. That invention may have been very recent, as recent as 40,000 years ago, with the first sustained evidence of culture, and the diaspora from Africa. And it may have been the invention of speech that was responsible for hemispheric differentiation, split consciousness and culture. Shift theory describes a process of sexual selection by the female for those males adept at evoking an aesthetic, feelings of feeling-part-of-something-larger-than-the-self, a tribal trance, a male low-testosterone hominid version of the chimpanzee demonstration, via their exhibition of skills in song and dance.
Goodall (1988) observed female and young chimpanzees watching male chimps performing a kind of rain dance. The rain dance, enacted at the beginning of a storm, had many similarities to the male conflict display, except in the dance, they performed in turn, not at each other, but with each other. They performed while being witnessed by the females and the young. In addition they performed a similar display at a waterfall within their territory (Goodall, 1990). The natural phenomena of the rain evoked feelings that the chimpanzees responded to by exhibition of movement and sound, males exhibiting to females.
Like the male song bird performing to gain a mate or define his territory, or the male chimpanzee performing a toned down demonstration to attract a mate, we are proposing that in these transitional hominid cultures the males danced (Hewes, 1973), gestured (McBride, 1973a,1973b; Corballis, 1999), and sang (, Darwin, 1871; Livingstone, 1973) during the communal celebrations or demonstrations, probably guided by rhythms (Fisher, 1992) of clapping, stomping, or percussion (Pfeiffer, 1982). The singers had no words, communication was accomplished by gesture or tone (Hewes, 1973), but they could elicit feeling with their skills. When males evoked beauty, they become attractive. Attractive males were chosen as mates. Their progeny carried forward potential talent in the form of the improved physical equipment for performing song. Before there was speech there was music; before the orator, the artist of the song. Language has its origins in art, evoking feelings of feeling-part-of-something-larger-than-the-self (Montagu, 1989).
A radical growth in brain size began approximately 2 million years ago, reversing about 30,000 years ago (Wiercinski, 1979). While song created a facility for speech, shift theory suggests dance helped create brain size increases. We believe that the ties between language development (Armstrong et. al., 1995), dance, and brain size increases, and developmental prolongation are four aspects or features of the same process when we understand that the female hominids engaged in female sexual selection were simply choosing males most likely to make it possible for their infants to survive.
The shaded area suggests relative brain size and species age.
adapted from (Ledyard G (1982) Darwin to DNA, Molecules to Humanity)
through John Eccles's, Evolution of the Brain: Creation of the Self
Harry Jerison (1973) describes correlations between brain size and predator/ungulate relations. Jerison proposes that predators have a larger brain than the animals they prey on because of the increase in skills required to pursue and catch an animal as opposed to eating plants and fleeing. The correlations are stark. If you eat other animals, if you are a hunter, your brain is bigger. Endurance and high acceleration are traits powerfully selected for to increase success as a hunter. Such skills require more brain mass.
But why so much brain growth and why so quickly if, indeed, it is the correlation with endurance and acceleration that is at least partly responsible for the changes? The answer lies with the early human female choosing mates brilliant in the dance.
The speed of these changes was breathtaking. The non-monogamous, non-polygynous sexual bonds in this early hominid culture made it possible for the speed of the changes described. Several women could choose to be impregnated by a single practitioner of the song, the dance, the hunt. The seed of a genius, a male with the talent to evoke profound feelings, could spawn a generation of children with his potential. In chimpanzee society, a single persevering, creative, and intelligent chimp will pass on more of his genes than a chimp less endowed (Goodall, 1988). In the hominid society, as in chimp and bonobo society (Goodall, 1988; Kano, 1992), the females shared in the decision to mate. Whereas in chimpanzee society males demonstrate provocative displays, in hominid culture this would have evolved into males creating an evocative demonstration. Testosterone driven aggression and sexuality in a chimpanzee-like hominid became a hormonally driven performance of dance. Grace, endurance and strength exhibited in the performance of dance in degrees far greater than actually needed to survive could be largely responsible, when paired with the influence of females choosing males with lower T, for the size of the brain we now have.
Whereas a hunter may have been selected by the female for his athletic skills, a dancer was unconstrained by tangible results. A dancer had no limit to the skill he could exhibit. In natural selection a predator is as enduring and agile as he needs to be to survive. In sexual selection the constraints on agility or endurance are unrelated to survival. A hunter brought back his catch to his sister's or his mother's house in the society we are describing. In this social organization the female's choice of a brilliant bringer-back-of-game would not benefit her own children. We are suggesting that she choose her mates for their ability to evoke feelings of feeling-part-of-something-larger-than-the-self.
Sexual selection based on an aesthetic increased the speed of evolution exponentially because the demonstrator of the art was practicing an intangible with no demonstrable ceiling in the exercising of the skill (Cronin, 1992). The criteria for success was not efficiency in staying alive or procuring food, it was in the "strange antics" so often referred to by Darwin (1871) in his discussions of sexual selection, the intangibles of song and of dance.
It has been hypothesized that early humans were selected for an ability to travel long distances, running, to chase down wounded prey. Spuhler (1979) outlined specific hormonal innovations that support this conjecture. We believe these glandular innovations are explained by dance as the driving force behind these changes.
Through dance and gesture, talented communicators in this "physical language" of hominids were selected for as mates because they engendered an experience characterized by feeling part-of-something-larger-than-the-self. These physical language users summoned a world that existed because of their skills, a world other people could temporarily occupy, a ritual/mythic world. Physical language evolved to the point that the teller could recreate an event, could reenact an earlier successful dance/song. We are not suggesting that there was language in the sense of a past/present/future or a narrative time frame. We are suggesting that individuals could communicate an experience.
Females picking males using specific criteria resulted in specific hormonal changes over time, creating a developmentally prolonged trajectory. In the female centered tribes we are describing, females had relatively high testosterone, which follows a model of bonobo chimpanzee society (Kano, 1992), where females are more domineering and often control societal relations through their sons. Male/female relations would have been far more androgenous than we know now. We would expect this to be reflected in less sexual dimorphism in the fossil record over this 2 million year period (Tanner, 1981; Miller, 1994), and then increased dimorphism in the last 40,000. This characteristic higher testosterone female/lower testosterone male is the hormonal constellation we will find in specific human populations existent today evidencing features that we hypothesize are characteristic of this hominid society; details shortly.
The dynamics of hormonally prolonging maturation have not been as specifically addressed as the mechanics of allometric scaling, differences in size. There are studies (Shea & Gomez, 1988) that have made it possible to describe the hormonal operation of size scaling. This paper does not address this area of study; we are exploring a different issue, relative rates of maturation and the onset and offset of those rates. We are following the influences of testosterone and estrogen and related hormones as the prime forces behind human evolution. Two related dynamics, neoteny and hypermorphosis, are the names of two maturation prolonging processes that describe the influence of these two hormones. We are hypothesizing that sexual selection in combination with dance and song propelled human evolution by prolonging maturation -- that art & sex, the core of spiritual experience, what we are calling the desire to feel part-of-something-larger-than-the-self, drove human evolution.
Louis Bolk proposed the theory that human beings are metamorphically prolonged as a result of a changed hormonal balance (Gould, 1977). Bolk described several characteristics of the human species influenced by this form of metabolic revision. He called this cluster of characteristics in humans, neoteny (a word coined by Kollmann in 1885). We suggest that successful communities had females that were attracted to males that exhibited neotenous characteristics. Neotenous characteristics of our species that include: larger head, longer life, smaller facial features in relation to skull size, a propensity toward play and wonder as adults, chubbiness in female adults, relative hairlessness, etc, could be a result of a female sexual selection process. Natural selection would powerfully select for the survival of communities with males with cooperative feelings, because males more involved with providing for and raising children would increase the likelihood of the children in those communities surviving to adulthood.
The bonobo are more neotenous than the chimpanzee, and humans, more neotenous than the bonobo. The influence of neoteny results in a more socialized male, an increased emphasis on sex, yet a decrease in aggression. These are behaviors associated with neotenous evolution that when reinforced by sexual selection can explain how the human species evolved, an explanation supported by patterns revealed by the neuropsychological literature.
Another way to look at this is that as males show increased evidence of neotenous behavior, there is an increased chance of that tribe's surviving, as males choose mates reflecting their own social, neotenous, somatic environment. Females are reinforced to choose neotenous characteristics in males (Fox, 1983; Badcock, 1991), in effect taming the males, not unlike the taming process that occurs in domestic animals. The Russian breeder, Belyaev, in twenty years, tamed a wild fox species by selecting for a single characteristic, animals that behaved tame (Budiansky, 1992). Belyaev selected for neotenous behavior and got, in addition, neotenous physical features including increased sexuality in females. The net result was that the animals with the most neotenous characteristics survived, they were the most social, the most useful.
There are a series of characteristics of human beings at issue here, some that explain influential elements of human character and the nature of culture. Neoteny, as a result of sexual selection, could explain why wonder and play established themselves so firmly in the behaviors of human adults relative to their evidence in the adults of other species. A number of authors have noted the potential association between neoteny and wonder in humans (Robbins, 1980; Montegu, 1989).
We have explored the influence of art and feelings-of-something-larger-than-the-self on the evolution of our species. We are proposing that the effect of the sexual selection/prolonged development feedback loop and the feeling of feeling-part-of-something-larger-than-the-self brought humans to a recent point in our pre-history, approximately 40,000 years ago. We emerged with big brains, an adept vocal apparatus, closely tied communities, and a metaphoric language of touch, gesture and dance. We hypothesize that this was an ambidextrous culture, characterized by a kinesthetic or physical language that used both hemispheres when communicating using symbol or metaphor, communicating often through ritual and myth. There was one tense (Whallon, 1989), no negatives, and only here and no where else, the same characteristics of dream, deep hypnotic trance: the unconscious (Bateson, 1972).
By applying the outcomes suggested by a sexual selection/neoteny feedback loop model to the origins of spoken language, a tentative hypotheses can be formed that explains how spoken language could have developed.