Fossils can provide a detailed record of early human skulls but, unfortunately, not of the brains inside them too.
Researchers worked hard and used genetic material prelevated from the fossils to look for clues about how the human brain evolved over the past few thousand years.
The way how they succeeded in growing human brain organoids, also known as “mini-brains,” that include the Neanderthal version of a gene known as NOVA1, a team of researchers reported in the journal Science.
Alysson Muotri, a professor from the University of California, San Diego and the Stanford Consortium for Regenerative Medicine, said:
“The archaic version of the gene changes the shape of these organoids.”
Instead of evolving into a smooth sphere, the Neanderthal organoids present an outermost layer that isn’t even.
Organoids with the new NOVA1 gene also seem to mature rapidly and remain smaller than their new counterparts, according to Muotri.
“The neurons start to get more active at very early stages,” he added.
The discovery is consistent with the hypothesis that the modern human developed big brains that keep on developing long after birth to progress in the complex social systems that we formed.
A brain that matures rapidly is more capable at birth. However, it’s less likely to keep on developing during childhood – the time when the modern human acquires a majority of the essential social skills.
Muotri and a vast team selected NOVA1 because it is one of a relatively restrained group of genes that evolved considerably since Neanderthals and Denisovans roamed the planet. Also, it is a gene known for its crucial role in the brain’s development.
Therefore, NOVA1 featured a “perfect” means of showing whether the ancient gene could shape the brain’s evolution, Muotri said.
To sort that out, Muotri and his team resorted to brain organoids, small clusters of brain tissue that can be grown in the lab and copy early brain development. However, Muotri claims that existing organoids only manifested the new, improved version of the NOVA1 gene.
“So we swap the archaic version for the modern version,” he added, with a common technique for gene-editing. Later, the scientists analyzed how brain organoids featuring the archaic version were unique.
Muotri explained that there is likely a reason why humans with the novel version of NOVA1 survived while those with past versions died out.
“It might suggest that sometime during evolution we acquired that mutation and it [did] bring us [a] tremendous advantage to be able to have this complex brain later in life,” he explained.
The concept received scientifical backup from researchers who’ve been analyzing the influence of Neanderthal genes that can still be found in many humans, particularly those with East Asian and European ancestry.
Dr Karen Berman said that it’s exciting to be able to use the knowledge of archaic DNA to delve into what makes humans who and what they are.
Her personal research proved that people with extra Neanderthal genetic materials usually tend to develop skills similar to those of Neanderthals.
Berman and her fellow researchers also found proof that Neanderthal genes prioritized the creation of brain networks dedicated to visual and spatial abilities instead of social interactions.
“It may have been the lack of these social networks” that caused the Neanderthal dying out.