Our Cheatin' Ancestors?

A new study suggests that modern humans are considerably less promiscuous than their forbears. In a story that appeared in the University of Oxford site, the culprit seems to be androgen levels:

Previous studies by the research team have shown that promiscuous species have low index to ring finger ratios while monogamous species have high finger ratios. High levels of androgens, such as testosterone, increase the length of the fourth finger in comparison to the second finger. It is thought that prenatal androgens affect finger length during development in the womb, which in turn is linked to adult behaviour. High levels of prenatal androgens are linked with competitiveness and promiscuity.

I would love to know what the r² on that analysis is. I am always extremely suspicious of a study that links a single process to a complex social behavior, especially something like this. Later, the article has this:

Dr Susanne Shultz, from the University of Oxford, said: ‘Social behaviours are notoriously difficult to identify in the fossil record. Developing novel approaches, such as finger ratios, can help inform the current debate surrounding the social systems of the earliest human ancestors.

They are notoriously difficult because they often leave few to no clues. This analysis also sidesteps the problems involved in trying to ascertain what other selective forces might have been at work in early hominid development. For example, in Ardipithecus, given that they exhibited incipient bipedality and were, at least in part, arboreal as well, there may have been selective pressures on metacarpal and phalanx length. Also, is finger length one trait dictated by pleiotropy? Or is it polygenic? Is there linkage disequilibrium going on? These sorts of questions could be extrapolated to other hominid species as well and need to be addressed before arriving at the conclusion that is stated in this study.

Complexity Can Evolve Without High Cost

Was R.A. Fisher wrong? It has always been thought that with complexity comes a general lack of evolutionary adaptability. The consensus about human evolution is that early primates were able to exploit their environments because they had a generalized bauplan and could adapt to whatever came down the road. This was true from the teeth to the skeletal structure. Now, in an article for Phys.Org, research by Jianzhi "George" Zhang and colleagues has challenged the idea that the evolution of complexity carries a high cost:

When Fisher first wrote about the cost of complexity, he argued that random mutations---which, along with natural selection, drive evolution---are more likely to benefit simple organisms than complex organisms.

"Think of a hammer and a microscope," Zhang said. "One is complex, one is simple. If you change the length of an arbitrary component of the system by an inch, for example, you're more likely to break the microscope than the hammer."

Looking at pleiotropy, the idea that individual genes can affect a range of traits, the authors found something surprising:

For simplicity, mathematical models of pleiotropy have assumed that all genes in an organism affect all of its traits to some extent. But Zhang's group found that most genes affect only a small number of traits, while relatively few genes affect large numbers of traits.

What's more, they found a "modular" pattern of organization, with genes and traits grouped into sets. Genes in a particular set affect a particular group of traits, but not traits in other groups.

In addition, the researchers learned that the more traits a gene affects, the stronger its effect on each trait.

And how does this relate to the topic of this blog? The author writes:

The new findings help buffer evolutionary biology against the criticisms of intelligent design proponents, Zhang said. "The evolution of complexity is one thing that they often target. Admittedly, there were some theoretical difficulties in explaining the evolution of complexity because of the notion of the cost of complexity, but with our findings these difficulties are now removed."

One of the general complaints that has been made against those who espouse ID is that there is either a persistently simplistic model of evolution employed or an incorrect one. Recent works by Michael Behe, William Dembski and Stephen Meyer have focused on the presumed inability of evolutionary models to account for "specified complexity." They also make the specious argument that there can never be an increase in information under these models. Studies like these, which operate out of a predictive model, show otherwise.

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