The Ledi-Geraru Jaw, Part 1

Hi Owl,

On Tuesday I mentioned that Donald Johanson hinted to some exciting news that would be released on Wednesday. I had planned to talk about this (very) exciting news on Thursday, but was quite ill
 and was not feeling up to doing such an important topic justice. I will try to tackle it tonight.

On Wednesday, it was announced that researchers in Ethiopia had found remains of a Homo habilis mandible that dated back to 2.8 million years ago. They are calling this the Ledi-Geraru jaw as it was found at the Ledi-Geraru research area in the Afar Regional State of Ethiopia, and scientists prefer descriptiveness over creativity when it comes to nomenclature. The bone was found by Chalachew Seyoum, an Ethiopian paleoanthropological student studying at Arizona State University, who first spotted a premolar during a walkover survey, and found that it was attached to a piece of a mandible. Other fragments of the lower jaw were found, along with four other teeth. The jawbone matched most closely that of Homo habilis. H. habilis is considered to be the oldest known member of the genus Homo, though there has been controversy over its categorization as Homo instead of Australopithecus, the genus to which Lucy belongs. The first H. habilis specimens dated from between 1.7-1.9 million years ago. Though older specimens have been found since then, this newest specimen, at 2.8 million years old, pushes the fossil record back considerably, and reshapes
the earliest views of our lineage as a genus.

Chalachew Seyoum holding his discovery

This is incredibly big news, and its significance is multifaceted. I cannot do it justice in the twelve minutes I have until my deadline, but I will resume this topic on Monday for a more complete overview of this discovery.

For tonight, here is an overview of the five biggest implications to come out of this finding.

1.) This fossil is 400,000 years older than any previously discovered fossil belonging to the genus Homo.
2.) It is possible that Homo habilis represents a split in the Homo genus to represent two separate evolutionary lines, one ultimately evolving into H. sapiens and the other dying out at some point but representing an entirely distinct evolution of the genus Homo.
3.) This further suggests that climate change may have driven to the adaptations that led eventually to early species of Homo.
4.) The origins of Homo in East Africa are now even more firmly supported by the fossil record.
5.) It has become clear that three distinct species of Homo existed, not necessarily simultaneously but in very close chronological proximity, between 2.1 and 1.6 million years ago: H. habilis, H. rudolfensis, and H. erectus.

The Ledi-Geraru jaw

This complicates the previously-understood landscape of human evolution, and could have significant implications for how we evolved. I am excited to learn more about this fascinating discovery, and I hope that you will keep reading on Monday for a deeper look at what this discovery means.

-Raven