If you try to analyze the difference between today's humans and Neanderthals, our closest relatives, and the Denisovans, you might not find any noticeable difference, at least for the Neanderthals.
According to ARS Technica, humans used sophisticated mechanisms, "made art and established themselves in some very harsh environments."
When modern humans first arrived on Eurasian scene, the numbers rose higher, spread further, and both the Neanderthals and Denisovans ended up being driven away or vanished.
Close Relatives
The said report specified that the "three species are close relatives," therefore, the number of differences in modern humans' proteins are comparatively small.
However, a large international research group used stem cells taken from modern humans for comparison. As a result, the research team found that the neural tissue comprises remarkable differences from the same tissue developed with today's human version.
As an initial step in their research, the study authors needed to decide on a gene they'd target. As earlier mentioned, all three species' genomes "are extremely similar."
More so, the similarity only rises when you look at those genome parts, encoding proteins. An additional complication is that some of the versions of genes found in Neanderthals still exist in a portion of the human population.
The researchers said that what they wanted to do is look for a gene where both the Neanderthals and Denisovans had one version, and almost "all modern humans had another."
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The NOVA1
As indicated in the study, out of tens of thousands of genes, the researchers identified only 61 that passed the said test. The one they opted to focus on was identified as NOVA1.
Despite its "explosive-sounding" name, NOVA1 was merely named after having initially been found linked to cancer, the Neuro-oncological ventral antigen 1.
Additionally, a look through the vertebrate family tree presents that the two ancient species are sharing a version of NOVA1 with "everything from other primates to chickens." This means that it existed in the ancestor of mammals and with dinosaurs.
Nonetheless, nearly all humans have a different gene version. In searching through a quarter-million genomes in a database, the team was only able to determine three examples of the Neanderthal version
The difference, as described in the report, "is subtle," exchanging in a closely related amino acid at one location in the gene, although "it is a difference."
However, the stud specified that NOVA1 is the type of gene where slight changes can have a huge effect. The RNAs used to make proteins are originally made of a combination of helpful parts split by useless spacers that should be spliced out.
What the Neanderthal Version Would Do in Human Species
Evidently, there are reportedly ethical issues with an attempt to see what the "Neanderthal versions would do in human species."
Nevertheless, some technologies developed over the past 10 years or so now enable humans to address the question differently.
First, the study authors were able to take cells from two different human species and have them converted into stem cells to develop into any cell in the body.
They then used CRISPR gene-editing technology to convert the gene's human version into the Neanderthal version.
After they performed extensive checks specifying that NOVA1 was the lone gene changed by the editing, the research team induced the stem cells to form neurons typical of the cortex of the brain.
The neural cell clusters that resulted were tinier in size when they were formed by cells "with the Neanderthal version of NOVA1," though such clusters had a more intricate surface shape.
Furthermore, the cells that had the Neanderthal version developed more slowly and tended to go through a process that ends in the death of cells more frequently.
Therefore, it was clear that the Neanderthal version changed cells' behavior as they were converted into nerve cells.
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