The human family tree just got even more complicated! Paleontologists recently found ancient teeth from two different human lineages at a site in northeastern Ethiopia. This discovery suggests that these ancient humans may have coexisted, reshaping our understanding of human evolution.
Kaye Reed, a paleoecologist from Arizona State University, explains that evolution isn’t a straight line from apes to modern humans. Instead, it’s more like a bush, full of branches that sometimes lead to extinction. This new find reinforces that idea.
The ancient group known as Australopithecus, which includes the famous fossil “Lucy,” existed long before Neanderthals or our direct ancestors. They were among the first hominins to walk upright. What’s fascinating is that these two lineages were likely evolving side by side more than 2.5 million years ago in eastern Africa.
Paleontologists made this remarkable discovery at a site called Ledi-Geraru. It’s already known for the oldest evidence of our genus, dating back about 2.78 million years. The new findings include teeth from another Homo species, around 2.59 million years old, and some Australopithecus teeth from about 2.63 million years ago. This marks the first solid evidence of Australopithecus in this part of Africa during that time.
Interestingly, Lucy’s lineage (Australopithecus afarensis) may have branched off just as our ancestors were emerging. However, fossil evidence for her species is scarce around the same time our genus appeared. The newly discovered teeth bring our ancestors and Australopithecus closer together in history.
Scientists are still trying to identify the exact species of the Homo and Australopithecus teeth, but the latter doesn’t match Lucy or others of her kind. Over the previous half a million years, much seems to have changed. As Brian Villmoare, the lead author of the study, notes, additional fossil discoveries are crucial to understanding the differences between these two lineages and how they might have coexisted.
Before this find, researchers suspected that these early human lineages overlapped in time, but concrete evidence was lacking. With these new teeth, the fossil record now fills an important gap between 2.5 and 3 million years ago.
The discovery increases the known number of hominins in eastern Africa to four: two types of Australopithecus, a robust offshoot known as Paranthropus, and the early Homo genus. Villmoare and his team conclude that the fossil record for hominins is more diverse than we previously understood.
This exciting chapter in our evolutionary history is just starting to unfold. The findings were published in the journal Nature, reminding us that the story of human evolution continues to develop with each new discovery.
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