R.I.P. Great Leap Forward
When I was a postdoc at Stanford in the mid-90s, Richard Klein loomed large in my pantheon of scientific heroes. He still does — Richard is an amazing font of information about all aspects of biological anthropology, and his textbook The Human Career is still one of my go-to references for all things human evolution-related. Reconnecting and getting to work with him more recently on reviewing and awarding Leakey Foundation grants has been a genuine pleasure.
Richard is known scientifically as a great all-rounder, but is perhaps best known to those outside of the field as the most ardent proponent of what Jared Diamond has called the Great Leap Forward (GLF). Taking its name from the ill-fated communist agricultural experiment foisted on the Chinese people by Mao Zedong in the late-1950s, the idea is that humanity went through a profound cognitive advance around 50,000 years ago — caused ultimately by genetic changes — that rapidly led to fully modern behavior. What came before the GLF was nasty, brutish and short, punctuated with grunts and chest-beating, while what came after was fully modern human behavior: art, complex language, advanced tool- and weapon-making technologies, and ultimately the conquest of the globe by a genetically distinct, better version of humanity.
The key distinction here is that modern humans are qualitatively different from everything that came before. And the archaeological record — the only way we have to assess our ancestors’ level of mental complexity — seemed to agree with this. The tools made by early members of the genus Homo were relatively crude up until around 100,000 years ago. The Acheulean stone tool industry lasted for well over a million years (starting around 1.5 million years ago), during which the designs changed very little. Its most iconic object, the Acheulean hand axe, is the longest-lasting technology that members of our genus have ever developed. Because the timing of the appearance of more complex tools roughly coincides with our arrival on the scene, archaeologists inferred that it took modern human ingenuity to create more complex tools. And art — well, of course that was only possible with a fully modern human brain!
Now, a new study of cave art from Spain throws a wrench into this tidy little narrative. Careful dating of ochre drawings found on the walls of several caves has yielded an astounding result: the artistic depictions predate the arrival of modern humans in Europe by at least 20,000 years. Along with earlier evidence for more primitive art-like creations at Bruniquel Cave in France, the takeaway is that we are not the first humans to create art — and therefore, by extension, we are not the first humans capable of abstract, creative thought. Neanderthals, it turns out, were far more similar to us psychologically than we ever suspected.
This is another in a series of incredible findings that have combined to shake anthropologists’ belief in human exceptionalism. When Louis and Mary Leakey discovered a primitive human-like skull at Olduvai gorge in 1960 in layers also containing crude stone tools, their reaction was to dub him “handy man” (Homo habilis in Latin), and their interpretation was that humans alone have learned to create tools. We now know this isn’t true, and that animals ranging from chimpanzees to crows also make tools, typically for obtaining food. Humans are like many other species in this capacity.
We have known for nearly a decade that modern humans and Neanderthals interbred — in other words, there doesn’t seem to be a biological barrier to mating, suggesting that perhaps we should all be considered part of the same species. Earlier taxonomic classifications actually referred to Homo sapiens neanderthalensis and Homo sapiens sapiens —mere branches of the same species, rather than qualitatively different taxonomic entities. OK, we said, we might look alike — but how alike are we behaviorally? Did Neanderthals talk, for instance? They seem to have had the throat structure — particularly the hyoid bone in the larynx — to produce speech, but our assumption was that the speech they produced was a depauperate version of our own, devoid of complex syntax and abstract conceptualizations. The evidence for this? Pretty thin. We pointed to the fact that Neanderthals never produced art — only modern humans can do that, we argued, so surely that accounts for the chasm separating us…or so we thought, until the new Spanish cave art dates were announced.
Where does this leave us? I’d like to suggest that we re-welcome Neanderthals into our own species and tear down the wall we’ve built between us and them since their discovery over 150 years years ago. There was no Great Leap Forward. All of the evidence is now telling us that there is a continuum of human variation — both genetic and behavioral — that connects us to our Neanderthal (and presumably Denisovan) cousins. They are far more like us than we would have suspected even a few years ago, and whatever attributes led to modern humans being the only members of our genus left alive on Earth, it wasn’t due to our fundamental genetic or behavioral superiority. Figuring out why we did ultimately prevail is now, more than ever, a vitally important question in human prehistory.
