So, this semester (Spring 2014), the Department of Anthropology at UNCG, along with the Departments of Biology and Interior Architecture, are organizing and hosting an Ashby Dialogue, which, through an endowment from the College of Arts and Sciences, "provide the opportunity for informal but focused inquiry into some topic or issue" of interest to university faculty and students. I helped a bit in the planning and organizing, but the lion's share of the work was done by our own Joel Gunn and biology's Malcolm Schug. Our theme for this semester is "Human Adaptation: Past and Future," and you can see the full schedule of events here. This is the first of several posts I'll provide throughout the semester as we progress through our program.
To kick off the schedule, we had hoped to have a talk from Greg Wray, a top-notch evolutionary biologist from Duke University who is interested in the evolution of gene regulation. Unfortunately, the winter storm (defined in North Carolina as a threat of snow or, in our case, an inch or so of snow) we had last week shut down campus and we had to cancel. Nevertheless, we did go forward with our first discussion session on Monday, February 3, and I'll recap that here.
The theme of our first session was How do Biologists Study the Question: What is the Evidence for Adaptation in Humans? There were a total of 10-11 people, including students from both anthropology and biology. We had posted a reading about next generation sequencing of genomes and two videos, one from Evan Eichler (Washington University) about structural variation in the human genome, and another from Sarah Tishkoff (University of Pennsylvania) about variation among modern African populations and evidence for the evolution of lactose tolerance, all of which served to focus our discussion.
We started off with an introduction from Malcolm, who gave us a great overview of the issue of genetic adaptation. He noted first that although "adaptation" can be viewed somewhat differently by anthropologists and biologists, Darwin's theory of natural selection and its focus on reproductive success serves to unite both fields. Biologists traditionally thought that because organisms appeared so well adapted to their environments that very little genetic variation would be present. This idea was blown apart by the work of Richard Lewontin and John Hubby, who in the 1960s documented a surprising amount of inter-individual variation in various proteins (this work was done first with flies and then, later, with humans). Further work by Martin Kreitman found tons of variation in DNA. All of this raised an important question: why the heck is there so much genetic variation between individuals if populations are supposedly well adapted to their environments?
Well, two answers emerged. One, which I'll dub the "adaptationist camp," thought that most of this variation was driven by natural selection (in this sense, inter-individual variation it is actually an adaptation in itself, since this variation will provide natural selection with something to work on). The issue then became to find the specific genes that were being selected for. The other side, which I'll call the "neutral camp," felt that most variation arises by random drift and alleles that have little or no effect on the survivorship of individuals. The debate was pretty acrimonious, but it seems like most folks recognize that both forces are probably at play.
To complicate matters further, Allan Wilson later suggested that perhaps it wasn't the genes themselves that were being selected for, but rather their regulation (i.e., when they are turned off and on, or how strongly they are expressed). Their is, for example, evidence that the human opposable thumb (the length of which permits us to manipulate small objects with ease) evolved not because of some structural change in a specific gene, but rather a change in when (and for how long) the genes responsible for the development of the hand were "turned on."
As Malcolm and our reading pointed out, the rapidly progressing genomic sequencing technology (it took years to sequence the first complete human genome about 15 years ago; we can now sequence entire genomes for everything from bacteria to human in DAYS) now permits huge amounts of data to be mined for evidence of natural selection. Now, geneticists can fish through whole genomes looking for gene that have undergone, or currently are undergoing, selection. I asked Malcolm how one goes about doing this, and he said that, essentially, geneticists scan the genomes of many individuals looking for allele frequencies that are higher (or lower) than expected (this can be determined statistically). I wonder if the technology is outpacing our ability to actually analyze it in a systematic way? Very interestingly, Malcolm told us about a study that simulated the evolution of a fruit fly genome and went back and identified "selected" genes with these statistical methods. Many were found, but the simulation did not include natural selection! So, it is by no means clear in every case whether or not genes have undergone natural selection.
Anyway, the clearest evidence for natural selection among most studies comes from genes identified with pathogen pressure and/or immune function and gametogenesis. Some other genes that appear to have been under selection over the course of human evolutionary history are FOXP2 (development of speech and language areas of the brain) and EDAR (development of several body tissues, including skin and sweat glands). We had additional conversations and discussions over pizza, including the issue of genetic determinism and how we define and analyze "traits."
Overall, a great start to our dialogues. I, along with Gwen Robbins Schug of Appalachian State, will be moderating our second session, which deals with past human adaptations to sedentism and urban life.
To kick off the schedule, we had hoped to have a talk from Greg Wray, a top-notch evolutionary biologist from Duke University who is interested in the evolution of gene regulation. Unfortunately, the winter storm (defined in North Carolina as a threat of snow or, in our case, an inch or so of snow) we had last week shut down campus and we had to cancel. Nevertheless, we did go forward with our first discussion session on Monday, February 3, and I'll recap that here.
The theme of our first session was How do Biologists Study the Question: What is the Evidence for Adaptation in Humans? There were a total of 10-11 people, including students from both anthropology and biology. We had posted a reading about next generation sequencing of genomes and two videos, one from Evan Eichler (Washington University) about structural variation in the human genome, and another from Sarah Tishkoff (University of Pennsylvania) about variation among modern African populations and evidence for the evolution of lactose tolerance, all of which served to focus our discussion.
We started off with an introduction from Malcolm, who gave us a great overview of the issue of genetic adaptation. He noted first that although "adaptation" can be viewed somewhat differently by anthropologists and biologists, Darwin's theory of natural selection and its focus on reproductive success serves to unite both fields. Biologists traditionally thought that because organisms appeared so well adapted to their environments that very little genetic variation would be present. This idea was blown apart by the work of Richard Lewontin and John Hubby, who in the 1960s documented a surprising amount of inter-individual variation in various proteins (this work was done first with flies and then, later, with humans). Further work by Martin Kreitman found tons of variation in DNA. All of this raised an important question: why the heck is there so much genetic variation between individuals if populations are supposedly well adapted to their environments?
Well, two answers emerged. One, which I'll dub the "adaptationist camp," thought that most of this variation was driven by natural selection (in this sense, inter-individual variation it is actually an adaptation in itself, since this variation will provide natural selection with something to work on). The issue then became to find the specific genes that were being selected for. The other side, which I'll call the "neutral camp," felt that most variation arises by random drift and alleles that have little or no effect on the survivorship of individuals. The debate was pretty acrimonious, but it seems like most folks recognize that both forces are probably at play.
To complicate matters further, Allan Wilson later suggested that perhaps it wasn't the genes themselves that were being selected for, but rather their regulation (i.e., when they are turned off and on, or how strongly they are expressed). Their is, for example, evidence that the human opposable thumb (the length of which permits us to manipulate small objects with ease) evolved not because of some structural change in a specific gene, but rather a change in when (and for how long) the genes responsible for the development of the hand were "turned on."
As Malcolm and our reading pointed out, the rapidly progressing genomic sequencing technology (it took years to sequence the first complete human genome about 15 years ago; we can now sequence entire genomes for everything from bacteria to human in DAYS) now permits huge amounts of data to be mined for evidence of natural selection. Now, geneticists can fish through whole genomes looking for gene that have undergone, or currently are undergoing, selection. I asked Malcolm how one goes about doing this, and he said that, essentially, geneticists scan the genomes of many individuals looking for allele frequencies that are higher (or lower) than expected (this can be determined statistically). I wonder if the technology is outpacing our ability to actually analyze it in a systematic way? Very interestingly, Malcolm told us about a study that simulated the evolution of a fruit fly genome and went back and identified "selected" genes with these statistical methods. Many were found, but the simulation did not include natural selection! So, it is by no means clear in every case whether or not genes have undergone natural selection.
Anyway, the clearest evidence for natural selection among most studies comes from genes identified with pathogen pressure and/or immune function and gametogenesis. Some other genes that appear to have been under selection over the course of human evolutionary history are FOXP2 (development of speech and language areas of the brain) and EDAR (development of several body tissues, including skin and sweat glands). We had additional conversations and discussions over pizza, including the issue of genetic determinism and how we define and analyze "traits."
Overall, a great start to our dialogues. I, along with Gwen Robbins Schug of Appalachian State, will be moderating our second session, which deals with past human adaptations to sedentism and urban life.
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