According to a recent study published on July 9, 2022 in the journal Molecular Biology and Evolution by researchers at the University of California San Diego School of Medicine, a collection of human gene mutations has been uncovered that prevents cognitive decline and dementia in older persons. The researchers honed down on one of the altered genes and tracked its history in the human genome from its first appearance. Homo sapiens may have developed this gene variation in response to contagious infections, such as gonorrhea, which prepared the door for grandfathers and great-grandfathers to exist in human social systems.
An eye on the long term
Humans are the only known species that has survived menopause. For this, the “grandmother hypothesis” says that older women are vital in helping to raise human babies and children since they need more care than infants of other species.
And now, experts are looking at altered genomes in an effort to better comprehend the long-term health of humanity. In the latest research, the sugar-binding region of CD33 was missing, showing that humans acquired a novel mutation along the evolutionary line. Sialic acid, a kind of sugar found on all human cells, binds to CD33, a receptor present on immune cells.
The mutant receptor no longer responds to sialic acids on injured cells or plaques, enabling the microglia to degrade them. CD33 variant has been shown to be protective against Alzheimer’s disease at a later stage. To figure out when this gene variant first appeared, scientists looked for signals of strong positive selection, suggesting that something was driving the gene to evolve faster than expected. This particular CD33 variation was not detected in the Neanderthals or Denisovans, our closest evolutionary relatives.