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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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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What’s in a Measurement? The Inside (and Outside) Story

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In our last two posts, Kristen and Sam discussed established ways to model the effects of evolutionary forces on skeletal traits. As they both mentioned, we often ask ourselves about whether what we are measuring best represents the traits we’re interested in modeling. At first glance, this may seem to be an esoteric issue, but as I’ll argue here, we should be cautious about measurement choice when we are trying to understand evolutionary change.

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