Evolution of Evolution — Text-only | Flash Special Report
Interview with Susan Antón
BOBBIE MIXON: One of the most fascinating aspects of evolutionary science is its relevance to the human species. Dr. Susan Antón is the joint editor of The Journal of Human Evolution and associate professor in the Center for the Study of Human Origins in the Department of Anthropology at New York University. Dr. Anton, you study changes in the human skeleton. In what ways have the facial features of Homo erectus changed during the last 100,000 years or so?
DR. SUSAN ANTÓN: Well, that's an interesting question and one that we are a little bit challenged to answer because there are so few facial skeletons in the fossil record. However, if we look at earlier species before Homo erectus, we see that the trend was for there to be relatively big jaws and big teeth and one of the things that had happened through the evolution of our genus, genus Homo, is that our teeth have reduced in size and our jaws have reduced in size and this is likely related to shifts in the kinds and quality of diet, the kinds of things that we've been eating so that we haven't been eating as tough and fibrous foods. Maybe we've been cooking our foods and that's resulted in the change in our facial skeleton.
BOBBIE MIXON: Now, have similar changes occurred for Homo sapiens?
DR. SUSAN ANTÓN: Well, there are some recent changes in the Homo sapiens. One thing that happens overall with Homo sapiens is that we actually get smaller and more gracile in all of our features, that is less robust in our features, and that is, in part, related to changes in diet and changes in cooking practices so that we process our foods quite a lot more and we don't have to put all of this force through our facial skeletons that our ancestors had to.
BOBBIE MIXON: How quickly can these changes occur?
DR. SUSAN ANTÓN: Well, it depends on the change and the strength of the selective pressure, but they can occur pretty rapidly. It depends on what change you're looking at, but if you look at things like body size, for example, we see that in recent humans, there have been so-called secular changes in body size that just over a couple of generations, maybe a couple of hundred years, you'll see changes in body size. Most typically you see this when you have offspring of parents where the offspring are getting a lot better nutrition than their parents were and they tend to be much bigger in size than their parents have been. You see this a lot in groups that have immigrated, say, to more industrialized countries.
BOBBIE MIXON: Now, Darwin viewed evolution as a slow, gradual process, but is evolution both slow and fast?
DR. SUSAN ANTÓN: I think that's right. There--again, depending on the selective pressures that are going on--things can change quite quickly with time, and it turns out that very, very small differences between individuals can be very important for the survival of an individual. So, one of the reasons, perhaps, that Darwin didn't see evolution happening during his lifetime is that he had convinced himself that it was a very slow process and so he didn't look for it to have occurred in the course of a single lifetime, but he might have been able to see it if he'd been looking closely at the morphology of the birds around his estate, for example. He noted that there were big climate crises where a lot of the birds died off and if he'd been looking at the birds before and the birds' skeletons afterwards, he might have seen that change through time, but he wasn't looking for it so he missed the sort of quick part of evolution.
BOBBIE MIXON: Now, some have noted that Darwin overstressed natural selection to make his case for human origins, but you say he vastly underestimated the power of natural selection. Who's right?
DR. SUSAN ANTÓN: Well, probably we're both right. In one sense, natural selection has gotten a lot of emphasis in evolutionary studies so that sometimes people forget that there are other very important processes that can result in evolutionary change so they forget about things like genetic drift and so on. On the other hand, the strength of natural selection and the quickness with which it can happen was probably stronger than what Darwin thought. So, I think both things are right. There are other forces of evolution and it's important to remember that not every feature that we see in a species is the result of a natural selective process, not every feature is the result of an adaptation to a particular environment and so on. On the other hand, natural selection can be a very, very quick and compelling force of evolution.
BOBBIE MIXON: Well, thank you for joining us.
DR. SUSAN ANTÓN: My pleasure.
BOBBIE MIXON: Anthropologist, Susan Anton, New York University.