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Why Were There Two ‘Bursts’ of Genetic Mutations in Ancient Humans?

Two 'Bursts' of Human Genetic Mutations Happened for Unknown Reasons

Researchers discovered two distinct “bursts” of changes in our human ancestors’ genes hundreds of thousands of years ago. Notably, the bursts happened around 600,000 years ago and 200,000 years ago for unknown reasons.

Thus, the first “burst” happened around the evolutionary split with Neanderthals around 520,00 to 630,000 years ago.

As reported by LiveScience:

 “…Exactly why the genetic changes occurred at those times — or what might have been going on in the environment to trigger those changes — is unknown.”

Now, what could have triggered the sudden bursts in brain growth? For now, it remains a mystery.

As incredible as this finding is, this part of the study was only a secondary focus in the article. 

Only 1.5% Unique to All Humans Today

Interestingly, the new study drew other amazing conclusions:

To determine which parts were unique to us, they used an algorithm to analyze 279 modern human genomes, two Neanderthal genomes, and one Denisovan genome. In the latter cases, the DNA came from fossils dating back to around 40,000 or 50,000 years ago.

Further, Richard E. Green, an associate professor of biomolecular engineering at the University of California, Santa Cruz, says around 7% of the human genome represents the portion “where humans are more closely related to each other than to Neanderthals or Denisovans.” 

Of interest, Green helped produce the first draft sequence of a Neanderthal genome in 2010.

Thus, the findings indicate humans were not that different from ancestors like Neanderthals. 

“That’s a pretty small percentage,” said Nathan Schaefer, a University of California computational biologist and co-author of the new paper. “This kind of finding is why scientists are turning away from thinking that we humans are so vastly different from Neanderthals.”

Recommended: Dragon Man: Giant-sized Ancient Human had Huge Eyes, Large Brain

Bursts of Mutations Involving Brain Development and Function 

Amazingly, of the small percentage that makes us unique, Green and colleagues recognized them. Tellingly, perhaps, the genes code for proteins involved in brain development and function.

Scientists can now study these specific gene mutations and could discover specifically how our brains differ from Neanderthals. Today, gene-editing technology has advanced to the point that scientists could turn back time in a way. 

Remarkably, Green suggested the possibility of flipping the human-specific genes in cells back to their “Neanderthal version” to see how the changes affected our history.

A Molecular Switch Affecting Brain Growth? 

Now, we know that a very small percentage of our genome is unique to all modern humans. Also, we know that 99% of our DNA is shared with our closest living relatives, the Bonobos and Chimpanzees. 

In March, scientists reported they discovered a molecular switch, causing primate brain tissue to grow more like the rate of a human’s brain. Due to how this molecular switch operates, our brains grow three times as large as an ape brain.

After the study, the researchers believe the gene switch Zeb2 may account for most of the size differences between human and primate brains. Thus, they called it an “evolutionary regulator.”

In a way that now sounds familiar given the news today, the hominid brain rapidly expanded after our ancient ancestors diverged from apes in the distant past.

New Ancient Ancestors

Notably, the studies showing what is unique to modern humans only included genetic material from Neanderthals, Denisovans, and Homo sapiens. As we know, there are other ancestors, with more evidence appearing recently.

Recently, researchers have revealed discoveries of new ancient humans that bred with our ancestors. In June, the news of the Nesher Ramla fossils from Ramla, Israel, indicated a new piece to our evolutionary puzzle. The fossils indicate a Neanderthal-like archaic that may have mingled with Neanderthals, Denisovans, and Homo sapiens.

In the same month, news about the “Dragon Man” from China broke. Some scientists believe the giant-sized skull with large eye sockets represents our “sister species,” while others believe he was an early Neanderthal.

Featured image by geralt via PixabayPixabay License

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