From fossil teeth to carbon traces of plants in the soil, scientists are studying how changes in climate may have influenced early human evolution in Africa. Researchers from around the world gathered for a symposium held recently at the Lamont-Doherty Earth Observatory. The workshop was organized by Professor Peter deMenocal, a paleoclimatologist at Lamont-Doherty and vice chairman of the Department of Earth and Environmental Sciences at Columbia. www.earth.columbia.edu