ASU News: The earliest evidence of our human genus – Homo – was found in Ethiopia by a team of Arizona State University scientists and students during field research in 2013.
The fossil, the left side of a lower jaw with five teeth, has been dated to 2.8 million years ago, which predates the previously known fossils of the Homo lineage by approximately 400,000 years.
The discovery is being published for the first time in the March 4 online version of the journal Science.
For decades, scientists who study the origins of modern-day humans have been searching for fossils documenting the earliest phases of the Homo lineage.
Researchers have found fossils that are 3 million years old and older. The most famous example of those human ancestors is the skeleton of Lucy, found in northeastern Africa in 1974 by ASU researcher Donald Johanson. Lucy and her relatives, though they walked on two feet, were smaller-brained and more apelike than later members of the human family tree.
Scientists have also found fossils that are 2.3 million years old and younger. These ancestors are in the genus Homo and are closer to modern day humans.
But very little had been found in between – that 700,000-year gap had turned up few fossils with which to determine the evolution from Lucy to the genus Homo. Because of that gap, there has been little agreement on the time of origin of the Homo lineage.
With this find, that mysterious time period has gotten a little clearer. [Continue reading…]
The Los Angeles Times adds: The significance of this discovery, according to some researchers, is that it firmly fixes the origins of Homo in East Africa and fits the hypothesis that climate change drove key developments in a variety of mammals, including our early forebears.
When Lucy roamed Ethiopia roughly 3.2 million years ago, the region enjoyed long rainy seasons that supported the growth of many trees and a wide variety of vegetation, according to researchers.
By the time of Homo’s first established appearance in the Horn of Africa, however, things had become much drier and the landscape had transformed into a vast, treeless expanse of grasslands with a few rivers and lakes — a scene very similar to today’s Serengeti plains or Kalahari.
It was an unforgiving climate when it came to survival.
But the hallmark of the genus that includes Homo sapiens is resourcefulness. Larger brains, the ability to fashion stone tools, and teeth suited to chewing a variety of foods would have given our early ancestors the flexibility to live in an inflexible environment, researchers say. [Continue reading…]