the Hammer Lab | Michael F. Hammer

The primary research goals in my lab are to better understand the genomic and evolutionary factors shaping patterns of human variation and to test models of human origins. The human genome holds clues to the mystery of human origins. With the recent completion of the first draft of the human genome sequence we are now in a position to examine patterns of variation across the entire genome in multiple human populations. Such an undertaking will facilitate an understanding of events that took place tens of thousands of years ago, and the better design of studies to map genes involved in human disease today.

Over the last decade, my lab has pursued studies of variation on the Y chromosome as a model system to explore human evolution. Now the lab is comparing patterns of genetic variation on the Y chromosome, mitochondrial DNA, X chromosome, and autosomes to distinguish the genomic footprint of natural selection from the signatures of demographic processes. We are engaged in a long-term collaborative project with scientists at USC to gather new data and design novel analytical methods to answ er long-standing questions in human evolution.

One focus of this research is on the evolutionary relationships of "archaic" human groups (such as the Neanderthals in Europe and Homo erectus in Asia) to modern humans. Did archaic forms make any contribution to the contemporary human gene pool, or were Neanderthals and H. erectus completely replaced (without interbreeding) by modern humans as they expanded out of Africa within the last 100 thousand years? Did our ancestors make the transition to modern form in a small, isolated part of Africa , or over a broader geographic range with genetic contributions from divergent populations?

Another focus of this research is on human population growth. Although our current population size is more than 6 billion, the long-term average population size was probably substantially less than 1 million. When did human populations begin to expand dramatically in size? Was this growth associated with a particular event in human history, such as the advent of language or the invention of agriculture? Our study design of 90 loci encompassing ~1.5 Mb on the autosomes and the X chromosome in 90 humans will reveal patterns of linkage disequilibrium and further our understanding of how and why recombination rates vary across the genome.