Becoming Human

In our occasional series, How Science Is Done, we attempt to show how real scientists, working on real questions, find answers - if not final answers, then suggestive answers that expand our knowledge into hitherto murky areas.

"Lucy" is the three million year old fossil discovered in the Afar region of Ethiopia in 1974 by Don Johanson. For more than three decades this remarkable find, which has told us so much about out origins, has been the subject of controversy.

Science is done in many ways.

A trail of footprints left in volcanic ash nearly four million years ago, corroborating the contention that Lucy was a biped, is threatened by both man made and natural damage in Tanzania, it was declared recently at a scientific symposium in South Korea.

By examining patterns of DNA variation in the genome for different human populations, we can determine how much of our evolutionary history was influenced by simple demographic change or, alternatively, by spurts of natural selection.

Teaser: Human offspring take more than twice the time to reach adulthood than do our closest living relatives, chimps and gorillas. This period of delayed maturation results in what we call the teenage years and is a characteristic of modern humans. Paleoanthropologists wonder how far back in the record of bipedal existence this delayed maturation commenced.

Dr Gary Schwartz, professor of paleoanthropology at the Institute of Human Origins, Arizona State University, is researching fossil teeth at the micron level and discovering what several million year old teeth can tell us about the individual whose teeth they were and how rapidly our earliest ancestors matured to adulthood as compared with other great apes.

Evidence of early humans living on the coast in South Africa, harvesting food from the sea, employing complex bladelet tools and using red pigments in symbolic behavior 164,000 years ago, far earlier than previously documented, is being reported in the Oct. 18, 2007 issue of the journal Nature.

In a paper appearing on September 20 in Science, analysis of the wrist bones of Homo floresiensis demonstrates this skeleton could not be a dwarf human, as has been argued. The paper also adds to the accumulating evidence the specimen is a strange mix of nearly modern and very primitive characteristics.

The suggestion interbreeding occurred between Neanderthals and Homo sapiens nearly 40,000 years ago, announced in papers published last November in both Science and Nature, has now been called into question.