Did This Gene Give Modern Human Brains Their Edge?
Did this gene give modern human brains their edge?:
More than 500,000 years ago, the ancestors of Neanderthals and modern humans were migrating around the world when a fateful genetic mutation caused some of their brains to suddenly improve. This mutation, researchers report in Science1,2, dramatically increased the number of brain cells in the hominins that preceded modern humans, probably giving them a cognitive advantage over their Neanderthal cousins.
"This is a surprisingly important gene," says Arnold Kriegstein, a neurologist at the University of California, San Francisco. However, he expects that it will turn out to be one of many genetic tweaks that gave humans an evolutionary advantage over other hominins. "I think it sheds a whole new light on human evolution."
When researchers first fully sequenced a Neanderthal genome in 2014, they identified 96 amino acids — the building blocks that make up proteins — that differ between Neanderthals and modern humans in addition to a number of other genetic tweaks. Scientists have been studying this list to learn which of these helped modern humans to outcompete Neanderthals and other hominins.
To neuroscientists Anneline Pinson and Wieland Huttner at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany, one gene stood out. The gene, TKTL1, encodes a protein that is made when a fetus's brain is first developing. A single genetic mutation in the human version of TKTL1 changed one amino acid, resulting in a protein that is different from those found in hominin ancestors, Neanderthals and non-human primates.
The team suspected that this protein could be driving neural progenitor cells — which develop into neurons — to proliferate as the brain develops, specifically in an area called the neocortex, which is involved in cognitive function. That, they reasoned, could be a contributor to modern humans' cognitive advantage over human ancestors.
To test this, Pinson and her team inserted either the human or ancestral version of TKTL1 into the brains of mouse and ferret embryos. The animals with the human gene developed significantly more neural progenitor cells. When the researchers engineered neocortex cells from a human fetus to produce the ancestral version, they found that the fetal tissue produced fewer progenitor cells and fewer neurons than it normally would. The same was true when they inserted the ancestral version of TKTL1 into brain organoids — mini-brain-like structures grown from human stem cells.
[...] Pinson says that the Neanderthal version of TKTL1 is very rare among modern humans, adding that it's unknown whether it causes any disease or cognitive differences. The only way to prove that it has a role in cognitive function, Huttner says, would be to genetically engineer mice or ferrets that always have the human form of the gene and test their behaviour compared with animals that have the ancestral version. Pinson says she is now planning to look further into the mechanisms through which TKTKL1 drives the birth of brain cells.
What Makes Your Brain Different From a Neanderthal's?
What makes your brain different from a Neanderthal's?:
[...] Our brain also has distinctive anatomical features. The region of the cortex just behind our eyes, known as the frontal lobe, is essential for some of our most complex thoughts. According to a study from 2018, the human frontal lobe has far more neurons than the same region in chimpanzees does.
But comparing humans with living apes has a serious shortcoming: Our most recent common ancestor with chimpanzees lived roughly 7 million years ago. To fill in what happened in since then, scientists have had to resort to fossils of our more recent ancestors, known as hominins.
Inspecting hominin skulls, paleoanthropologists have found that the brains of our ancestors dramatically increased in size starting about 2 million years ago. They reached the size of living humans by about 600,000 years ago. Neanderthals, among our closest extinct hominin relatives, had brains as big as ours.
But Neanderthal brains were elongated, whereas humans have a more spherical shape. Scientists can't say what accounts for those differences. One possibility is that various regions of our ancestors' brains changed size.
In recent years, neuroscientists have begun investigating ancient brains with a new source of information: bits of DNA preserved inside hominin fossils. Geneticists have reconstructed entire genomes of Neanderthals as well as their eastern cousins, the Denisovans.
[...] The new finding does not mean that TKTL1, on its own, offers the secret to what makes us human. Other researchers are also looking at the list of 96 protein-changing mutations and are running organoid experiments of their own.
[...] "I don't think it's the end of the story," he said. "I think more work is needed to understand what makes us human in terms of brain development."
Journal References:
Pinson, A. et al. Science 377, eabl6422 (2022). DOI: 10.1126/science.abl6422
Malgrange, B. & Nguyen, L. Science 377, 1155–1156 (2022). DOI: 10.1126/science.ade4388
(Score: 3, Insightful) by PinkyGigglebrain on Tuesday September 13 2022, @07:56AM
now we know how the Monolith did it.
"Beware those who would deny you Knowledge, For in their hearts they dream themselves your Master."
(Score: 1) by shrewdsheep on Tuesday September 13 2022, @08:10AM (1 child)
... gave us Batteridge
(Score: 2) by c0lo on Tuesday September 13 2022, @09:09AM
Yeah, and Billie, and her kid (who is not my son) too.
Just remember to always think twice
(grin)
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by HiThere on Tuesday September 13 2022, @01:40PM (2 children)
There are definitely several genes in the surviving hominid linage (i.e. humans) that gave a survival edge.
OTOH, I don't really think that the Neanderthals or the Denisovians were separate species. More regional varieties. We know they interbred. And we know that several of our genes come from the Neanderthal variety, and a few from the Denisovian. And that both varieties shared a very large number of genes with the Cro-Magnon variety. And we're what survived out of that mix. The hominid varieties were a LOT less different than Chihuahuas, Saint Bernards, and Dachshunds.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by dltaylor on Wednesday September 14 2022, @01:31AM (1 child)
There are populations in sub-Saharan Africa (and, perhaps, pre-European Australians) that have no Neanderthal or Denisovan DNA. Unless the research is specifically looking at mixed-descent traits, they should use those populations as the baseline for "modern" humans (ironically called "homo sapiens sapiens", despite all of the evidence to the contrary).
(Score: 2) by HiThere on Wednesday September 14 2022, @01:33PM
I don't know why you think Native Australians would fit that category. The Denisovians seem to have been quite common in south-east Asia. Unless you think the native Australians got there directly from Africa by boat.
But, yes, those were regional varieties. The Neanderthals seem (to me) to have originated north of the Black Sea, and perhaps a bit west of it. The Denisovians in south-east Asia. They both spread out from their points of origin. So it's quite reasonable that populations in southern Africa should not have their genes in its mix. (IIUC, they had their own regional varieties, some of which left traces in their genomes, but which are not tied to any identifiable fossils.)
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 3, Informative) by Zinho on Tuesday September 13 2022, @01:54PM
As long as they hold off on repeating the research on rats... [goodreads.com] we should be good.
"Space Exploration is not endless circles in low earth orbit." -Buzz Aldrin
(Score: 2) by legont on Wednesday September 14 2022, @01:38AM
Correct me if I am wrong, but I believe that liberal science proved that smartness does not depend on neither bran's size nor form. Did the authors of the article compared their findings to diversity of modern humans brain shapes? I guess not.
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.