Every assumption has been called into question over the last fifteen years, Colin Barras tells us:
Do you believe that human brains have been getting steadily bigger for millions of years, culminating in the extraordinary machine between your ears? Think again, because over the past 15 years, almost every part of our story, every assumption about who our ancestors were and where we came from, has been called into question. The new insights have some unsettling implications for how long we have walked the earth, and even who we really are. Once upon a time, the human story seemed relatively straightforward … It began roughly 5.5 to 6.5 million years ago, somewhere in an east African forest, with a chimpanzee-like ape. (paywall) More.
One’s first and probably wisest reaction is not to bet the farm on the new story either. The new story, behind the paywall, covers such topics as
– “layer upon layer of complexity and confusion” around newly discovered species that date back to 5.8–7 million years ago. Humans and chimps, many now think, could have split as early as 13 million years ago.
– It’s not clear that early humans were swinging in the trees. “Ardi” at 4.4 mya was walking upright. Chimps may have gained that ability later.
– Stone tools have been found from 3.3 million years ago. “In any event, determining which hominins evolved into humans is no longer as clear-cut as it once was.”
And so on. An obvious problem is that there just aren’t very many fossils. As Neanderthal genome mapper Svante Paabo has observed, there are more paleontologists than important fossils in the world. This isn’t so much a second draft of human history as a few more notes found on scraps of paper. But any progress in such a case means knocking down numerous false certainties, which is a start.
See also: The Science Fictions series at your fingertips: Human evolution