I'm an anthropologist, and I study the bones and genes of ancient humans. I was trained as a paleoanthropologist. ``Paleoanthropology'' is more than a speciality within anthropology, or biology. It is an integrated study involving methods and insights from many fields. Unlike many paleoanthropologists, my study extends across the entire span of human evolution, the last 6 million years, as I examine the genetic and environmental causes that made the foundation of our origins.
My academic position is Associate Professor of Anthropology at the University of Wisconsin—Madison. I am starting my seventh year in Madison.
Paleoanthropology:
What does it mean to be a paleoanthropologist?
To use evidence from the fossil record, we must be trained in human anatomy -- especially
bone anatomy, or osteology. We have to know the anatomical comparisons between humans and other primates, and the way these anatomies relate to habitual behaviors. The social and ecological behaviors of primates vary extensively in response to their unique ecological circumstances. Understanding the relationship of anatomy, behavior, and environment gives us a way to interpret ancient fossils and place them in their environmental context.
Ancient environments were not the same as the ones we can explore today. These environments included different plants and animals, and they underwent large climatic shifts over time. Learning about the environmental context of human evolution. This is the subject matter of geology and paleontology, which are also essential to understanding the chronology of events in the past.
Integrating human biological evolution with the record of human behaviors requires a knowledge of archaeology. Stone tools and human-modified animal bones are the earliest record of our behavior. But some of the most recent evolutionary changes in humans happened at a time when people lived in cities and grew agricultural crops -- an even broader area of archaeology, ranging into history.
My doctoral advisor was Milford Wolpoff, who is well known as an innovator of the "multiregional" theory of modern human origins. But one of the reasons why Milford was so interesting to me as a student was his work on nearly every time period in human evolution -- ranging from the earliest hominids up to the evolution of modern humans. The integrative view across different time periods focuses on evolutionary theory and mainstream biology, not the particular hypotheses relating to any single event. I have been able to take this broad perspective in my own work -- I've written papers about the earliest hominids, later australopithecines, the origin of the genus Homo, Neandertals, modern human origins, and evolution within modern humans of the Late Pleistocene.
Statistical approaches to fragmentary samples
Skeletons don't generally come out of the ground whole. And there aren't very many of them. That means we need ways to compare and make conclusions based on bits and pieces. Every problem in paleoanthropology is to some extent unique, because it depends on a unique combination of the bits and pieces. My unique ability is figuring out how to make valid comparisons out of this mess.
Sometimes this means working out boundary conditions for valid comparisons. That is to say, sometimes the data look like an evolutionary trend happened, but how can we know that the "trend" isn't just the way the bones happened to fall into the ground?
For example, a lot of people used to think that Neandertals in Europe became stranger and stranger-looking over time. Their increasing anatomical "specialization" was taken as evidence that they were evolving separately from other humans -- the two groups were proposed to be more and more different into the last ice age. But together with Milford, I was able to show that Neandertal features weren't becoming more specialized. Instead, Neandertals seem to have maintained a fairly consistent degree of difference from other human populations throughout their existence, with many features evolving in the same pattern in Neandertals and other humans.
This was a case where understanding the evolutionary theory was essential to interpreting the pattern of anatomical evolution. Clearly, Neandertals and other humans were different. But how much difference is expected between populations that share a common pattern of evolution? And how much difference does it make that the small samples of these populations come from different times and places? Those are the kinds of questions that I answer.
Population genetics
Population genetics is the mathematical theory of evolutionary change. It major development occurred during the 1920's and 1930's by Ronald Fisher, Sewall Wright, and J. B. S. Haldane. The concepts of population genetics were integrated into the study of biological evolution during the 1930's and 1940's, and the study was consolidated as the "Synthetic Theory" of evolution.
I'm a bit of a fundamentalist about genetics. A lot of interesting strings were dropped by Fisher and Wright, and didn't really get woven into the synthetic understanding of populations. I've been working on picking up a few of these. Additionally, the later development of genetics by people like W. D. Hamilton, John Maynard Smith, and C. H. Waddington created new opportunities to examine the evolution of populations over time. But for the most part, their theories have been examined in a static context, without a consideration of their dynamics over time.
If you're training to be an anthropologist, some of this probably sounds strange and foreign to you. It's OK. Read some Dobzhansky, that will give you a start.
My current work has involved two of these dropped threads of theory -- one related to the introgression of selected alleles onto new genetic backgrounds, and the other...well, the other is a secret for the moment. Introgression is a possible model for a number of genes that appear to document the genetic survival of Neandertals into later European populations. The idea that a gene could be plucked from an ancient population and actually succeed in a later population
Anthropological genomics
During the past few years, I have spent an increasing proportion of my time working with data from the Human Genome Project, the International HapMap, and other projects that have generated information about the workings and variation of multiple genes.
Ten years ago, we were lucky to be able to assess the variation of a single gene within more than one human population. I, like many other people, spent much effort trying to distinguish the effects of natural selection and ancient human demography on a single gene. Most people who know anything about human genetics will remember those days well -- nearly 10 years spent arguing about what mitochondrial DNA could say about modern human origins, without any substantial information from any other gene! My dissertation tried to test hypotheses about ancient human demography using information from four genes. That was a major innovation!
The missing connection in genomics is the historical and prehistoric record of human evolution. Both recent and ancient evolutionary changes in genes had effects on human phenotypes. Genomics has recently made two things very clear. First, the kind of variation between people is heterogenous -- with different genetic systems showing different patterns of variation. Second, the pace of change during human evolution was not uniform.
This is the most active area of my research, and so I can say the least about it. Last year, I published a paper titled, "Recent acceleration of human adaptive evolution," which documented a massive increase in the rate of evolution in the last 30,000 years. By some measures, human evolution has been proceeding at a rate a hundred times faster than ever before. Together with several other colleagues, including Gregory Cochran, Henry Harpending, and Robert Moyzis, we continue to look for evidence of recent adaptive changes. We hope to discover some of the genetic changes that have made recent humans different from ancient hominids like the Neandertals, in addition to making us different from each other.
Other stuff
My scientific work hasn't been limited to genetics and fossils. Lately, I have become more and more interested in the problems of cultural transmission and information theory. This is part of my "first principles" approach to problems in prehistory -- I think that we have to build an account of the origins of culture that is based in the simplest rules of information transfer.
In a sense, these issues are very similar to the issues of genetic transfer and the evolution of human genetic variation. However, with genetics we are beginning with a very well-defined system with rules that have hardly changed since the Paleocene. The content in humans is new, but the system is old.
With culture, we have a very new system, certainly novel in primates, that has been rapidly changing. The transmission properties are not well defined, and our ability to pick up information has recently rapidly evolved. Why? What were the factors that led to these new adaptations? How do the problems of information transfer relate to the human perception and use of signs? What are the connections between information theory and semiotics in the origin of culture?
It's an interesting problem, and since none of it is secret, I've been writing about it a bit.
