Neanderthals are being resurrected after 40,000 years of extinction. Well, sort of.
Scientists at the University of California, San Diego (UCSD) are using CRISPR technology to grow pea-sized Neanderthal brains in petri dishes. The plan, reports Live Science, is to find out why exactly this particular hominid species died out all those years ago – and why our early modern ancestors did not.
Did climate change kill the Neanderthals? Or disease? Some have suggested early humans mated their cousins to extinction. (In the words of the late Freddie Mercury, “love kills”.) Others say the steady trickle of Homo sapiens out of Africa "doomed" the Neanderthals.
One hypothesis, which comes up time and time again, is that it comes down to brain size and structure. In summary, their intelligence and social skills were no match for those of our ancestors. And it is this particular debate the team at UCSD hopes to settle.
The research was presented at a conference called Imagination and Human Origins, held at UCSD on June 1. It is yet to be published.
The team used Neanderthal DNA data – previously collected from fossils and then sequenced into a digital genome – and compared it to DNA data from modern humans. They decided to concentrate on one particular protein-coding gene, NOVA1, out of a possible 200. This gene plays a crucial role in early brain development and is associated with neural conditions including autism and schizophrenia. Interestingly, its expression is almost identical in both Neanderthal and human DNA. Only one base pair separates the two.
The next step involved building the brains. The process of growing organs (or organoids) in a lab (or, indeed, in a pig, a rat, or a sheep) is not in itself new but in order to “Neanderthalize” the mini brains, the scientists used a gene-editing technique (CRISPR) on human stem cells. After six to eight months, the brains – or “Neanderoids”, as the scientists call them – are “mature” and measure roughly 0.5 centimeters (0.2 inches).
The researchers noted important differences between the Neanderoids and modern human equivalents. For example, there were fewer connections between neurons in the Neanderoids. Those that were there looked different, much more like autistic brains, explained Muotri, who has a stepson with the condition.
"I don't want families to conclude that I'm comparing autistic kids to Neanderthals, but it's an important observation," he told ScienceMag. "In modern humans, these types of changes are linked to defects in brain development that are needed for socialization. If we believe that's one of our advantages over Neanderthals, it's relevant."
The shape was also different. The Neanderoids had a “popcorn-like” appearance. In contrast, modern human brain organoids grown in labs tend to be circular.
It's all very interesting but there are limits to the research. Organoids are not directly comparable to a fully formed adult brain, the Max Planck Institute for Evolutionary Anthropology's Svante Pääbo pointed out, adding, “There are lots of control experiments to do, and then I'm quite hopeful we'll overcome those doubts." His team is also conducting research on Neanderthal brains using similar methods.