Friday, October 18, 2013

A new hominid fossil may simplify the story of human evolution

My goal this year was to get into a habit of posting something interesting every week. Considering that it is now October and I have posted nothing since school started, I would say that I have not exactly succeeded. But failure is no excuse for giving up and this story sounds like a pretty major development in the area of human evolution. The original study is in Science, but most of the good stuff is behind a pay-wall. The BBC has a pretty good write-up though with some good pictures and an interview with the leader of the research team. What they found was a skull from a hominid that lived about 1.8 million years ago in what is now the Dmanisi region of Georgia. There are at least two things that are interesting about the find. First, it is a nearly complete skull including most of the face and brain-case and even most of the teeth. No skull that is this old has ever been found in such good condition. Second, the scientists are not sure how to classify it because it possesses features that are characteristic of several previously identified hominid species. This means that the skull is either a hybrid of several different species or that those groups are not really different species at all and the differences among them simply reflects individual variation. In support of the latter hypothesis, other skulls have been found in the same area over the years that are from a similar time period and show considerable variability when compared to each other.  
The most likely explanation is that all these individuals are members of a single population of a single species. If that is true, it would suggest that many of the hominid fossils that have been found in Africa and Europe are members of the same species and not of separate species as they have been classified in the past. This is a common problem in paleontology: whenever multiple individual fossils are discovered that are not exactly like each other, it is hard to tell if they are members of the same species. Sometimes, two individuals that are considerably different from each other are placed in separate species only to be reassigned to the same species once more specimens are found that share characteristics of both groups.

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