HAS climate change made us who we are today?
A broken and fossilized jawbone found poking from the sediment of an East African hill is rewriting a significant chapter of human evolution—and adding weight to the argument that a hot and parched climate guided the development of our ancestors.
In a pair of papers published on Wednesday in the journal Science, researchers described the discovery of a 2.8-million-year-old jawbone in Ethiopia’s Afar regional state.
Studded with five intact teeth, the mandible reveals that our genus, Homo, appeared almost half a million years earlier than previously believed, after branching off from the more apelike Australopithecus genus that included the likes of “Lucy,” perhaps the most famous set of skeletal remains.
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 about 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.
“This early Homo could live in this fairly extreme habitat and apparently Lucy’s species could not,” said Kaye Reed, an Arizona State University paleontologist who worked on both studies.
The record of early Homo evolution in Africa is notoriously sparse. Erosion, tectonic shifting and other factors have left very few remains for scientists to study.
As a result, even the fragmentary jaw found at the Ledi-Geraru site is cause for celebration.
Monte Morin / Los Angeles Times/TNS