How far back in time must we go for our ancestors to not be human and be, instead, an ape walking on two legs? What’s needed to qualify as “human”?
Getting to the bottom of this is more complicated than it appears, says Tanya Smith, a human evolutionary biologist at Griffith University.
Alongside fossils and other archaeological remains, traces of Neanderthals and Denisovans are found today as stretches of DNA in our genome, remnants of interbreeding through the ages — not just with us, but with each other too.
So, Professor Smith says, instead of thinking of our species’ evolution as a “family tree” — with branches splitting into two species, then going on to split again or become a dead end — think of it more like a braided river, where multiple water channels diverge, flow for a bit, then come back together.
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The likely “first human”, she says, was Homo erectus. These short, stocky humans were a real stayer in human evolutionary history.
Estimates vary, but they’re thought to have lived from around 2 million to 100,000 years ago, and were the first humans to walk out of Africa and push into Europe and Asia.