When Science Times debuted 40 years ago, scientists knew far less about how our ancestors branched off from other apes and evolved into new species, known as hominins.

Back then, the oldest known hominin fossil was a diminutive, small-brained female unearthed in Ethiopia named Lucy. Her species, now known as Australopithecus afarensis, existed from about 3.85 million years ago to about 2.95 million years ago.

Lucy and her kin still had apelike features, like long arms and curved hands. They could walk on the ground, but inefficiently. Running was out of the question.

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Hominin evolution appeared to have taken a relatively direct path from her to modern humans. The earliest known members of our genus, Homo, were taller and had long legs for walking and running, as well as much larger brains. Eventually, early Homo gave rise to our own exceptional species, Homo sapiens.

Now, it’s clear that Lucy’s species wasn’t the beginning of our evolution; it was a branch that sprouted midway along the trunk of our family tree. Researchers have found fossils of hominins dating back over six million years. Those vestiges — a leg bone here, a crushed skull there — hint at even more apelike ancestors.