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

November 16, 2017 by Kristen Savell in Evolution, Human evolution, Quantitative genetics, Variation

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.

Monkeying around with Morphospaces

October 31, 2017 by Samuel Williams in Evolution, Ornstein-Uhlenbeck, Phylogenetic modeling, Quantitative genetics

In my last post, I introduced the concept of a morphospace – the bounded range of possible shape variation that exists for a given trait in either one population of organisms or a trait shared by several related populations of organisms. Morphospaces are crucial to understanding morphological (shape) variation in two important ways: 1) determining how past evolutionary forces have acted to produce a particular morphology, and 2) predicting how current and future evolutionary forces will alter that morphology over time. In this post, I write about studying the first concept in traits that might capture facial shape change in response to climatic variation among macaques. What I found, however, was surprising.

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

June 05, 2017 by Angela Mallard in Human evolution, Variation, Quantitative genetics, Evolution

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.

Uncanny Resemblances: When a Heating Coil is like an Adaptive Peak and a Golden Retriever is like Random Genetic Drift

February 13, 2017 by Samuel Williams in Quantitative genetics, Ornstein-Uhlenbeck, Phylogenetic modeling, Evolution

Some of the most interesting questions in evolutionary biology arise from both unexpected diversity and unexpected similarity among organisms. Sometimes organisms are genetically similar, yet display outward characteristics (phenotypes) that can be strikingly different. Other times, organisms display phenotypes that are astonishingly similar despite greater genetic distances.