In a massive genomic study with data from 210,000 people in the United States and Great Britain, a team of researchers from Columbia University, the New York Genome Center and the University of Cambridge (USA) has discovered that the Genetic variants linked to Alzheimer’s disease and smoking are less common in people with longer life expectancies , suggesting that natural selection is eliminating these unfavorable gene variants in both populations. Thus, despite our mixture of intelligence and self-awareness, the evidence seems to show us that natural selection continues to shape our species: we continue to evolve.
The experts also found that the sets of genetic mutations that predispose people to heart disease, high cholesterol, obesity and asthma, also appear less frequently in people who lived longer and whose genes are more likely to be transmitted through the population. The results have been published in the journal PLOS Biology.
“ It’s a subtle signal, but we found genetic evidence that natural selection is taking place in modern human populations,” said Joseph Pickrell, a co-author of the work.
Over time, we have been able to see how genes have come and gone to allow us to adapt to our environment. About 10,000 years ago, for example, a change in the HERC2 gene gave us the first display of blue eyes, a trait that is now quite widespread in some parts of the world.
There is no reason to think that humans are no longer under the influence of natural selection, even if that selection often feels less natural and more ‘urban’ (such as the fact that our decision to live in cities has selected genes that reduce the risk of contracting diseases such as tuberculosis and leprosy ).
To see how our current genes are contributing to our fitness as a species , and to gain a better understanding of how we will continue to evolve into the future, the scientists combined data from 57,696 individuals from Genetic Epidemiology research into the Health and Aging Study of Adults with details of the parents of 117,648 UK Biobank participants.
The experts found a marked decrease in the prevalence of a mutation in a gene called CHRNA3 (associated with the nicotinic acetylcholine receptor / smoking) among men from middle age, indicating a reduction in nicotine addiction in the male population. human genome.
We keep evolving
Another gene variation that seems to be slowly abandoning us is ApoE ε4, which encodes a type of protein that carries cholesterol and supports the repair of lesions in the brain. Carrying this variation of the protein increases the likelihood of developing Alzheimer’s and the study found a significant decrease in the presence of the gene in women older than 70 years.
Although none of the discoveries is surprising, the researchers hoped to find more dangerous variants of each of these genes. The failure to detect any suggests that these genes may have already been purged from our species.
“It may be that men who do not carry these harmful mutations can have more children, or that men and women who live longer can help with their grandchildren, improving their chances of survival,” explains Molly Przeworski, co-author of the work.
As tempting as it is to extrapolate these findings into predictions about how our species might look in the distant future, it’s important to note that our environment – including medicine and technology – can always throw us a ‘wild card’ (or two).
“ The environment is constantly changing . A trait associated with longer life expectancy in today’s population may not be useful after several generations,” says Hakhamanesh Mostafavi, leader of the work.
Thus, human beings are still far from controlling our own genetic destiny as we are still immersed in the evolutionary process.
Reference: Hakhamanesh Mostafavi, Tomaz Berisa, Felix R. Day, John RB Perry, Molly Przeworski, Joseph K. Pickrell. Identifying genetic variants that affect viability in large cohorts. PLOS Biology, 2017; 15 (9): e2002458 DOI: 10.1371 / journal.pbio.2002458
