In an institute in Germany, scientists are growing “Neanderthalised” human brain cells in a dish. These cells form synapses and spark as they would have done in a living Neanderthal as she (they are female cells) foraged or breastfed or gazed out of a cave mouth at dusk. That is the spine-tingling opening gambit of a book co-authored by one of the directors of the institute, Johannes Krause, and the information that sets it apart from a host of popular science books that attempt to predict humanity’s future based on our evolutionary past.
A mere 90 genetic differences distinguish modern humans, Homo sapiens, from Neanderthals, Homo neanderthalensis. That’s paltry, given the roughly 20,000 genes that make up the human blueprint, and not all of them affect the brain. Yet those 90 differences could explain why Neanderthals died out, some 40,000 years ago, while we went on to dominate the planet. They could hold the key to how we, the apparently more adaptable human type, might adapt again before we destroy the ecosystems we depend on, and ourselves along with them.
That, at least, is the rationale behind the German experiment. In order to really understand the effects of the differences, the scientists would need to build whole organs, ideally whole Neanderthals, and then compare them to modern humans on a suite of measures. Since they agree with most of the rest of us that this would be morally objectionable, they make do with rudimentary brains, so-called brain organoids (the Guardian’s science correspondent describes them as “lentil-sized” and “incapable of thoughts or feelings”). Building these already poses a technical challenge, and it will be a few years before they have completed the task.
Most of the rest of the book is given over to an update on the history of human evolution, which is something of a moving target at the moment, thanks to the 20-year-old technology that made it possible to extract and read DNA from ancient bones. The story gets more complicated with almost every telling, but one message comes through loud and clear: most branches of the human family were evolutionary dead ends. The only one that survived to the present day, us, very nearly didn’t. Something gave sapiens an edge, but what was it? Culture? The ability to build large social networks? A utopian dream and a kamikaze approach to realising it? Or chance?
Whatever it was made us aggressively expansionist, and nowhere were our expansionist tendencies more impressive than in Austronesia. Starting in Taiwan about 5,000 years ago, our ancestors cast off from a succession of overcrowded islands with animals, seeds and children on board, but no guarantee that they would glimpse the next piece of land within thousands of miles of ocean. The time came when modern humans had occupied every last atoll, then every last scrap of the habitable planet. Now we’re looking hungrily to the moon and Mars.
The biological urge to perpetuate one’s genes is not distinctively human; we share it with every other organism. Curiosity isn’t an exclusively human trait either; apes strayed out of Africa long before us. Nor were we always rapacious. The authors repeat a long-held claim that Easter Island, Rapa Nui to its original inhabitants, was stripped bare by those inhabitants’ descendants, who thereby ensured their own demise. But new research has questioned that interpretation, finding that people lived sustainably there prior to the arrival of Europeans in the 19th century.
We did survive all the other hominins, though, and that needs explaining. Krause and Trappe’s argument accommodates the Rapa Nui rethink, because they claim that it was only in the 20th century that Homo sapiens became Homo hubris – when the exponential growth in human population, technological innovation, mean global temperatures and biodiversity loss transformed us into an existential threat to ourselves. That transformation happened so fast that it must have been the product of cultural rather than biological evolution, but the capacity to adapt through culture ultimately lies in the genes.
The authors say there is no evidence that Neanderthals made art, which if true might imply that they were less capable of abstract thinking than us. Not everybody would agree with that, but most would concede that Neanderthals differed from us linguistically and cognitively. The question is: can we leverage those differences to rein in our avaricious impulses before it’s too late? Can we mobilise culture to override biology?
In case anyone needs reminding, that means coordinating the behaviour of 8 billion already-born for the good of the still-to-be-born. We’ve failed dismally so far, but maybe we still have it in us. Or maybe the real hubris is to think that we are anything other than a dead end waiting to happen. The Neanderthals roamed the planet for nearly 400,000 years; we have been here for 300,000. When all is said and done, who will be judged the winner (and who will judge)?
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