How Mitochondrial Eve rewrote human evolution

This month marks the twenty-fifth anniversary of the discovery of Mitochondrial Eve, the common ancestor of every human alive today. Here’s everything you need to know about why the mother of humanity is so important.

In January 1987, Rebecca Cann, Mark Stoneking, and Allan Wilson published a paper in Nature that dropped a bombshell of our understanding of human evolution. Until then, the prevailing theory held that different groups of humans had evolved separately in different regions, beginning about two million years ago. Their groundbreaking work revealed all humans carried mitochondrial DNA in their cells that dated back to a single woman who had lived just 200,000 years ago. This woman was dubbed Mitochondrial Eve.

Though their research was initially met with tremendous controversy, the death knell of the multiregional hypothesis had already been struck. The idea here was that our predecessor Homo erectus had left Africa two million years ago and spread out around the entire world. Then, these different populations adapted to their new environments by evolving into Homo sapiens, although constant gene flow and interbreeding between these different populations meant that everyone remained part of the same species. This model was seen as the best way to explain all the Homo erectus fossils found throughout Africa, Eurasia, and Australia.

The discovery of Mitochondrial Eve gave crucial support to the Recent African Origin model, which held that modern humans only evolved once, most likely in East Africa, somewhere between 150,000 and 200,000 years ago. All older fossils discovered elsewhere represented hominid lineages that had since gone extinct. And while we’ve recently seen some strange fossil findings that could complicate the picture yet again, the basic tenets of the Recent African Origin model are now well-established.

So how did Mitochondrial Eve manage to rewrite the entire story of human evolution? For that matter, what exactly is Mitochondrial Eve? Unlike her biblical namesake, she wasn’t the only woman on Earth. In a sense, she’s just a quirk of statistics. But if that’s the case, then she’s easily the most important quirk of statistics who ever lived.

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