Monday, May 18, 2009

Sexual Selection

I will be posting some games as soon as I settle on a PGN viewer which I wont struggle to understand. In the meantime i've been reading alot of Darwin lately, specifically his under-represented work "The Descent of Man and Selection in Relation to Sex"

Charles Darwin had a hard time buying the idea that the differences in human ethnic groups could be accounted for strictly through natural selection. His research is often over-looked for fears of backlash on the motivations of the research. Darwin even made sure to be careful how he approached the subject, but in the end realized that scientific solutions to unanswered questions were paramount to the advance of evolutionary theory.

Natural selection runs into problems as an all-encompassing solution to human variation.If it could in fact explain the most basic of racial differences:skin color, and eye color, hair, we should in fact see that trait eventually in other parts of the world with similar environmental conditions. Scientists could then come to a conclusion on say... the advantage of blue eyes, as opposed to competing eye colors.

The run of the mill explanation is that skin color is largely influenced by the rays of the sun. In fact it is true that if those with light-skin stay in the sun too long they will increase their chances of skin cancer. Therefore it makes "obvious" sense that this is the main reason for skin variation in the equatorial regions where sunlight is at its maximum strength.

But truth be told skin cancer causes very few deaths, even when light-skinned peoples are exposed to the sun for extended periods. As the author Jared Diamond puts it "As agents of natural selection, they have an utterly trivial impact compared to infectious diseases of childhood (the Third Chimpanzee 114)". I wont get into the ideas associated with vitamin D deficientcies and over-absorbtion, just know that the theory runs a similar vein with little natural selection measures to back it up.

The deepest objection revolves around the idea that the connection between dark-skin and sunny environments is very inconsistent. Another J.D. example revolves around the fact that natives of tasmania have very dark skin even though they live in an area with very little sun light. Even in equatorial South American you don't get any dark skin attributes resembling sub-saharan African skin tones.

The objection to this complain is the time factor. Some have suggested that there hasn't been enough time for these traits to take hold. If that is the case then how do we account for blonde haired, blue-eyed Scandinavians? They have only been able to populate these northern areas for about 9,000 years. That is since the pirmafrost receeded and we start finding human remains. Why is it that we find such diverse variation in Scandinavians so quickly? the answer seems to be posed by Darwin.

Sexual Selection

Here is a quick peek at what others have said in regards to S.S.

Charles Darwin conjectured that the male beard, as well as the relative hairlessness of humans compared to nearly all other mammals, are results of sexual selection. He reasoned that since, compared to males, the bodies of females are more nearly hairless, hairlessness is one of the atypical cases due to its selection by males at a remote prehistoric time, when males had overwhelming selective power, and that it nonetheless affected males due to genetic correlation between the sexes. He also hypothesized that sexual selection could also be what had differentiated between different human races, as he did not believe that natural selection provided a satisfactory answer.

Geoffrey Miller, drawing on some of Darwin's largely neglected ideas about human behavior, has hypothesized that many human behaviors not clearly tied to survival benefits, such as humor, music, visual art, verbal creativity, and some forms of altruism, are courtship adaptations that have been favored through sexual selection. In that view, many human artefacts could be considered subject to sexual selection as part of the extended phenotype, for instance clothing that enhance sexually selected traits.

Some hypotheses about the evolution of the human brain argue that it is a sexually selected trait, as it would not confer enough fitness in itself relative to its high maintenance costs (a quarter to a fifth of the energy and oxygen consumed by a human).Related to this is vocabulary, where humans, on average, know far more words than are necessary for communication. Miller (2000) has proposed that this apparent redundancy is due to individuals using vocabulary to demonstrate their intelligence, and consequently their “fitness”, to potential mates. This has been tested experimentally and it appears that males do make greater use of lower frequency (more unusual) words when in a romantic mindset compared to a non-romantic mindset, meaning that vocabulary is likely to be used as a sexual display (Rosenberg & Tunney, 2008).

The evolutionary biologist Richard Dawkins has speculated that the loss of the penis bone in humans, when it is present in other primates, may be due to sexual selection by females looking for an honest advertisement of good health in prospective mates. Since a human erection relies on a hydraulic pumping system, erection failure is a sensitive early warning of certain kinds of physical and mental ill health.

The photo of this Japanese "blonde" is interesting as individuals have been able through cosmetic techniques to aquire traits for Sexual Selection. The Japanese being on an isolated island for 1,000s of years lack the genetic diversity that many ethnic groups hold. Differentiation is now able to be enhanced by hair dyes, color contact lenses and a large assortment of easily accessible methods to stand out and attract a mate.

In the past this wasn't the case. Humans were able to select traits of which specific groups found to be attractive and then cultivated those traits within the population.

I will go into more detail at a future time. This is a primer for more advanced discussion on this and other topics.

My next post may be strictly Chess based!

1 comment:

  1. Great to see you back. Chris. I'm trying out Chess Flash. There is a link in my latest post to it. I like your first two posts very much. I, too, am interested in ideas and often feel like I don't fit securely into one group or another on some of the Great Questions.