The Identity of the Amino Acid That Wiped Out Neanderthals
1)
Genetically, there is little difference between archaic humans such as Neanderthals and Denisovans and modern humans (Homo sapiens). However, the key factor that determined the fate of modern humans to evolve significantly was a single amino acid within an enzyme produced by a particular gene.
2)
Humans have a gene called ADSL, which produces the ADSL enzyme essential for brain and nerve development. However, the 429th amino acid in the 484-amino acid chain of this enzyme differs between Neanderthals, Denisovans, and modern humans. In their case, alanine is present at that position, while in ours, it is valine.
This chemical variation may have brought about significant changes in our subsequent behaviour, according to a research team from the Okinawa Institute of Science and Technology Graduate University (OIST) and the Max Planck Institute for Evolutionary Anthropology.
3)
Photo caption:
From top to bottom, the gene sequences of the ADSL enzyme in modern humans, Neanderthals and Denisovans, chimpanzees, and mice. The 429th amino acid in modern humans, shown in red, is different from the others. The 428th mutation in mice did not affect the function of ADSL.
4)
It is known that defects in the ADSL gene can cause delayed motor development and cognitive impairment. Additionally, it is said that if the ADSL enzyme is overly active, it may cause the brain to mature too quickly or become overly excited.
5)
Another genetic variation has been found in the ‘non-coding region’ involved in gene expression between archaic humans and Homo sapiens (also found only in modern humans), but the amino acid substitution, in combination with this variation, is thought to cleverly slow down the growth rate of the brain so that it develops properly, while suppressing the activity of the ADSL enzyme to a degree that does not cause ADSL deficiency.
6)
OIST used mice with a substitution of the 429th amino acid in the ADSL gene to verify behavioural changes. When given a task where they could drink water after visual or auditory cues, only the female mice with the amino acid substitution drank water more frequently than other mice born from the same parents.
This indicates that they can act advantageously in competition for limited resources. In other words, they have become smarter.
7)
While acknowledging that the results of mouse experiments cannot be applied to humans, Dr. Xiangchun Zhu, the lead author of the study and a researcher at OIST, stated, ‘There is a possibility that evolutionary advantages were conferred in specific tasks.’
A single invisible amino acid substitution within a single gene led to the extinction of Neanderthals and Denisovans, while we thrived. It is unclear what factors determine destiny.
The Identity of the Amino Acid That Wiped Out Neanderthals
https://forbesjapan.com/articles/detail/81131
