You have reached my professional webpage, which documents my exploits as a theoretical evolutionary biologist and as a Professor at the Santa Fe Institute. If you were trying to reach me as a person, you can go now to my less professional personal web page, or, if you are a glutton for punishment, to my even less professional blog.
Still here? Then I will proceed by assuming that you want to know more about my research interests. I am very broadly interested in evolutionary processes, which I study through a combination of mathematical and computational modeling. That is, I tend to work on questions that have one of the two following forms: (1) Here is something surprising or counterintuitive in the world; can we understand why natural selection would have produced that? (2) Here is a large quantity of data (e.g., genetic or linguistic); how can we make inferences about the process that gave rise to the patterns that we observe in that data?
In terms of specific content, I am interested in a few different areas, which are described briefly here. More detailed descriptions can be found by following the links the menu on the left. That menu will also let you access various downloadables, including my CV, PDF copies of papers, and code for the simulation and analysis of genetic data.
Genomic Imprinting and Intragenomic Conflict
The term genomic imprinting refers to the phenomenon where the expression pattern of an allele depends on its parental origin. That is, at an imprinted locus, the maternally and paternally derived gene copies will behave differently, even if they share the identical DNA sequence. The most successful theory of the evolutionary origins of genomic imprinting is based on the idea of intragenomic conflict. In general, the effects of natural selection are not identical for maternally and paternally derived alleles. If the asymmetry of selection is sufficiently strong, alleles can evolve two different conditional expression strategies.
I am particularly interested in the functional consequences of intragenomic conflict at the level of the individual organism. Genomic imprinting, like other instances of intragenomic conflict (e.g., segregation distorters), can lead to antagonistic coevolution among loci, even if it results in maladaptive consequences for the individual. Of particular interest are the imprinted genes that are expressed in the brain, and are associated with a variety of cognitive and behavioral phenotypes. Antagonistic coevolution involving these genes may contribute to certain major psychiatric disorders, such as autism and schizophrenia, as well as self-deating behaviors related to, for example, inconsistent time preferences.
Geographic structure plays an important role in shaping the patterns of genetic diversity in most species. Simply put, offspring tend to be born in geographic proximity to their parents. The combination of limited geographic dispersal and genetic drift leads, over time, to a correlation between genetic similarity and geographic distance. This correlation can be found within species (the phenomenon of isolation by distance), plays a critical role in many speciation events, and has repercussions even at higher taxonomic levels (e.g., the geographic distribution of Marsupials).
Many models of geographically structured populations focus on the case of discrete subdivision into distinct subpopulations, or demes, that are connected through migration. My work has focused primarily on models of isolation by distance, where the population occupies a continuous habitat, but intergenerational dispersal is limited. I am particularly interested in systems where intraspecific competition plays only a minor role in local population density regulation, and in how the shape and degree of habitat heterogeneity interact to generate an "effective dimensionality" of dispersal.
I am also interested in a number of other things, most of which involve collaborations, some of which have progressed to the point of scientific publication, some of which are still on their way. These include statistical approaches to historical linguistics, the effects of modeling frameworks on the interpretation of evolutionary outcomes, the evolution of recombination hotspots, and the structure of prehistoric human populations.