By meLo, 1340 words
Usually within the HBD community, discussions regarding the main mechanism(s) that drove the expressions of particular phenotypes is centered around natural selection or ecological(in the strictest, most traditional sense) factors. Sexual selection is unfairly sidelined, even though sex is the base of all multicellular evolution. The point of this article is to provide a logical argument for Sexual selections tremendous involvement, and to provide examples of how these pressures have shaped neolithic and modern Homo sapiens. I excluded Australoids but for good reason. Even though the population does have sexual selected traits, like blonde and culry hair, they are an incredibly diverse group and with the amount of pocket isolation I don’t think it’s fair without breaking this group into more categories. I kept this paper short, because it’s my first one and I wanted to use this as a “prototype” for future posts. Again all criticism is more than welcome because I myself am still learning about this topic.
First, it is important to note that traits which evolved from sexual selection are not the same thing as traits that serve reproductive purposes. Reproductive organs are usually the product of sexual selection, but sexual selection does not always act upon genitalia. Sexual selection favors any trait that allows an organism to attract the opposite mate more effectively, competitively or not.
The general trend
Before I explain the respective pressures and phenotypes between subpopulations of the neolithic, it is essential to begin with a summary of the temporal trend that persisted before the aforementioned groups. This begins with a breakdown of definitions and the repair of misconceptions. Human development is extremely complicated, so this explanation will have oversimplifications for the sake of efficiency. Any questions or discussions on the matter are more than welcome. If you don’t know anything about heterochronies I suggest you read this.
Paedomorphosis=/= Neoteny. Neoteny is a heterochronic process, paedomorphism is a type of heterochrony. One of the largest or most noticeable differences between Homo sapiens and Chimpanzees is the increase in paedomorphic and peramorphic traits of the former. All heterochronic mechanisms affect the developmental outcome of homo sapiens this is mostly to do with developmental trade offs and creates a mosaic pattern of our evolution. Humans have accelerated brain growth which reaches full size before most of the other limbs and organs are finished, even though this is achieved through peramorphic heterochronies it coincides with the deceleration of the body which actually produces a more paedomorphic appearance in the population. This acceleration ends(progenesis) and is subsequently followed by a strong deceleration(neoteny) of the skulls growth (Penin, 2002). Neoteny and acceleration define growth rate, but the actual duration of the growth period is hypermorphic, meaning the duration of Human growth is delayed or extended so that our legs and brains can continue to grow. Even though the brain is not paedomorphic its still enlarged to retain its childlike plasticity.These processes underlie the “direction” of our evolution, and while a lot of important traits are a result of peramorphic processes, it would be foolish to disregard the obviously paedomorphic traits we exhibit. It doesn’t take long to see how sexual selection can favor peramorphic or paedomorphic traits. Peramorphosis tends to create exaggerated features(think Irish Elk, Peacocks or the human brain) while paedomorphosis tends to appeal to sexual selection by producing “fragile” traits associated with infants of the species, in theory members of the opposite sex should associate these traits with “cuteness” and possibly even better parental skills.
Most don’t realize, but all races have undergone sexual selection. Each race has its own unique combination of peramorphic and paedomorphic traits as well as superficial ones that don’t relate to heterochrony. I will briefly go over each race and describe the varying degrees of pressures and the resulting phenotypes.
Caucasoids have the largest concentration of hypermorphic traits. They are the tallest race, and have the most color variation, this heavily implies sexual selection is involved. While height only has a small correlation with IQ, taller specimens will generally have larger brains, because they also have larger bodies. It also been documented that taller individuals tend to be seen as more attractive. Blue eyes are disproportionately present in the scientific community and they are a recessive trait, it’s speculative but very possible that blue eyes coincides with increased intelligence. Peter frost already did most of the work for me, you can read his piece on European sexual selection here. Mate competition becomes the obvious reason for these phenotypic expressions.
Unfortunately there isn’t much data on penis size, as a result this description will be lackluster. Which is usually the go to trait that HBDers look for when defining the sexuality of Africans. Things like Breast and buttocks size are ill defined, and studies on them are rifled with misconceptions. What we do know though, is that blacks are around the same height as Europeans but the majority of groups tend to have smaller brain sizes. It is interesting to point out that Africans display more paedomorphic facial features(except for prognathism). This makes a lot of sense, Africans are more r selected than Caucasoids, so it is expected that they display more paedomorphic traits. Because of a lack of data, I can’t make a reasonable assessment on the pressures that could of caused these expressions, however I do not think it would be far fetched to assume that it is also mate competition.
Pygmies, are a result of what Shea 1984 calls “rate hypomorphosis” Essentially it is a truncation of allometric scaling. Pygmies should therefore be one of the least intelligent and most r selected races. Their body and brain size decreased from the ancestral one, and they are almost entirely paedomorphic. More than likely their body size has to do with their adaptation to fewer resources. Capoids can confuse a lot of people. At first I thought they must be intelligent because of their paedomorphosis, but their brains are only a measly 1270cc and according to the Shea and Penin studies(cited earlier) a lot of traits considered to be paedomorphic(flat nose, reduced prognathism) are actually just the result of functional innovations and are independent of developmental growth. Specimen like Homo sapien Idaltu then begin to make more sense. The pressure involved here is more than likely an increased need of childcare(or at least a decrease in aggression) but not necessarily and increased need of Intellectual faculties.
Along with pygmies they are the most Paedomorphic race, and one of the most r selected. East asians have proportionally short limbs, very baby like faces, and the largest brains of any race. More than likely this is due to shape retardation following neoteny(deceleration of growth). It is necessary to define why Capoids and Mongoloids share similar facial traits yet do not share the same body proportions or absolute brain size. In this situation it is reasonable to assume that both populations had similar pressures for childcare and decreased aggression the main difference is hypothesized to lie in the varying survival pressures each group faced, I believe the ecological factors in East asia were more cognitively demanding than in Southern Africa, not in the sense that Africa is an easier place to survive but that Eurasia had a higher demand for Neuroplasticity. This is for two main reasons 1) in a novel environment there is more that you are required to learn and 2) The founder effect makes recessive genes easier to be expressed.
Intelligence can arise from a multitude of factors and no factor is completely necessary. Caucasoids seem to have developed their intellect from mate competition and K selection. Negroids are similar but to a lesser degree. Mongoloids seem to have evolved their cranial capacity for primarily docility and cooperation. All are forms of sexual selection, just for different preferences in attraction. Europeans and Africans tend to gravitate to more masculine features while Capoids, and Mongoloids are more for feminine ones.