What's in a (Quantifiable) Trait? Of Evolution, Evolvability, and Human Variation

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One of the challenges of understanding evolution is determining what makes a trait meaningful for a research question. Quantitative genetics literature in general gives limited guidance on this point, as any quantitative trait simply needs to be a quantifiable quality of an organism, and not a discrete class; it needs to have a continuous distribution and be measurable on a scale. For a trait to be applicable to evolutionary quantitative inquiry, it needs to be heritable. What often is missed is that the degree to which such traits are able respond to selective pressures is itself an evolvable trait, a quality we term "evolvability." Since we have evidence that the correlations between measures of body form have strongly affected human evolution across ecogeographic regions, I decided to see if the measures of evolvability between these human populations would notably differ.

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What’s in an Age? [Guest post from Dr. Alice Gooding, Kennesaw State University]

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Are we really doomed to mechanical and material breakdowns in our skeletons shortly after we reach adulthood? It is true that bone loss with age in humans is nearly universal. It has been documented worldwide in both living and past populations, as well as non-human primates. And though bone loss may begin after bones fuse, it accelerates during mid-life (after age 40) and continues after mid-life in humans. Increased bone loss is concurrent with an increased risk of fracture, decreased mobility, and even in industrialized societies, increased mortality. Why do humans live long past the years when bone loss begins?

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A Melting Pot, or Just a Salad? Evaluating Population History Through Gene Flow

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Gene flow is superficially a simple concept; we may liken this evolutionary mechanism to a melting pot. At a fundamental level, when individuals from two defined groups exchange genes, these populations have experienced gene flow. New gene(s) are introduced into one or both populations, and the population becomes more diverse through an increase in genetic variance. When teaching evolution at an introductory level, we generally conclude our explanations at this point.However, identifying gene flow in the past is considerably more difficult.

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Dynamic Duos: Why Examining More Bones is (Mechanically) Better Than One

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A common question raised in research by morphologists and functional anatomists is, “How do we better understand the movement of this creature?” From the work of earliest naturalists, descriptions of the shape and size of bones were key aspects to this research endeavor. Further, because of the fragmentary nature of the fossils of many ancient organisms, scientists learned to draw conclusions from isolated or a few skeletal elements. Perhaps because of decades of using this approach, we have grown accustomed to examining certain single bones over others, even when we have completely intact skeletons to consider. Yet, examining one element may be ignoring subtle but important contributions that better explain variation in the morphology of multiple bones.

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