Day By Day

Friday, September 21, 2007

The Missing Links

A few days ago John Noble Wilford, the grand old man of science journalism, published a summary article in the New York Times on the subject of human evolution. The gist of the article was that attempts to reconstruct the line of human development has been stymied by a million year "gap" in the evidence. Prior to three million years ago there is ample evidence for a variety of bipedal apes [Australopithecus] and from approximately 1.8 million years ago there are several specimens representing at least two species of human [Homo Habilis and Homo Erectus] prior to the emergence of Homo Sapiens. What is missing, though, is direct fossil evidence for the first humans. Because of this paucity of evidence, the article asserts, there is a great deal of controversy that can only be cleared up by further investigation [trans: more money for more expeditions]. Not surprisingly, several major figures in paleo-anthropology endorse this conclusion.

Read the article here.

John Hawks, however, disagrees to some extent. He points out that:

1) Abundance of evidence does not quiet controversy. There is a lot of controversy over how to interpret the abundant Australopithicine fossils prior to three million years ago.

2) There is no paucity of evidence from the period three to two million years ago. Evidence of tool manufacture dates from about 2.6 million years ago and is probably associated with the first representatives of the genus homo. This gives us important information regarding the mental capacity of these first humans as well as clues to their diet [they were meat-eaters]. Moreover there are plenty of ape fossils dating from this period, some of which have human-like characteristics. What are scarce are specifically human remains. This is not an absence of evidence, Hawks argues, it is evidence -- showing that despite changes in diet and tool-making capacity, early humans were quite restricted in their range for several hundred thousand years. Their new behaviors did not confer upon them a decisive advantage over contemporary ape species. That is an important finding.

If Hawks is right, more funding for more expeditions is unlikely to turn up very many more human remains from the gap period, and is unlikely to add much to what we already know, which is that the emergence of genus homo was associated with important behavioral and dietary changes that did not immediately confer decisive advantages on the first humans.

Somehow, with money at stake, I doubt that his position will prevail in the short run.

Read Hawks' commentary here.