These scientists were shocked when they compared the genomes of humans and monkeys for the first time. The latter evolved at a speed a good third faster than ours! Moreover, while mutations in monkeys accelerated over time, those in humans slowed down. What do we think? That we've reached a threshold? That our closest relatives are catching up to us and are acquiring mutations faster than we thought we were the only ones to benefit from so far? One more narcissistic wound for humanity?
Ine date that scientists have never been able to agree on is the date of our separation. Our primate ancestors lived on the same tree and one day one of them decided to be a man. The apes led their lives on one side, and the men on the other. How long ago was this great separation? 11 million years ago according to some specialists, 6.6 million years ago according to other experts. The date actually depends on what scientists call speciation; that is, when a species has acquired enough genetic mutations to become a new one.
The genome no longer holds any secrets
In recent years, researchers have become very comfortable deciphering the genome. In particular, the human genome no longer holds many secrets for them. Over the past six years, several large-scale studies have sequenced the human genome so that we have a thorough understanding of the number of new mutations that have occurred over the generations in the human population. The sequencing of the genome of entire families has made it possible to discover new mutations by exploring genetic variants that are present only in children and not in parents. This has fascinated us with our own genetic material for as long as we've been able to study it, and we've done some pretty careful work not only to map our genes, but also to determine how quickly they change.
On the other hand, our knowledge is much poorer when it comes to monkeys. Until now, there were no good estimates of the rates of genetic mutations in our closest primate relatives such as chimpanzees, orangutans or gorillas. This gap has been filled with the work of researchers from the University of Aarhus and the Copenhagen Zoo. Their work has just been published in the journal Nature Ecology & Evolution.
Comparative mutations
Scientists collected genetic information on the parents and offspring of chimpanzees, gorillas and orangutans to compare their mutation rates with ours. An analysis of their DNA sequences revealed how many new mutations appeared in each generation, allowing the team to compare the numbers between the various branches of the primate family tree.
By comparing their data with similar data collected on humans and carefully taking into account the relative differences in the ages of the parents, the scientists were shocked. The mutation rate in each of the great ape families studied was on average about 150 % higher than ours.
Moreover, while mutations in monkeys accelerated over time, those in humans slowed down. Researchers have found that this slowing has occurred in the most recent period, in the last million years.
The higher rates of genetic mutations in great apes have an impact on the time that has elapsed since the common ancestor of humans and chimpanzees lived. A higher mutation rate means that the number of genetic differences between humans and chimpanzees accumulates over a shorter period of time.
Applying the new mutation rates to monkeys, the researchers estimate that the speciation that separated humans from chimpanzees occurred about 6.6 million years ago. Using the mutation rate recorded in humans, the speciation should have been around 10 million years ago.
However, the new study is formal, the separation between apes and humans occurred much less long ago than previously thought, perhaps even as recently as 400,000 years ago.
When we know that genetic mutations are closely correlated with lifestyles and especially with the environment, this new research opens up interesting avenues to better understand how a species adapts to changes that may affect its genes. These results could also have an important impact on the conservation of great apes. Christina Hvilsom of the Copenhagen Zoo explains: "The results of this research will help us to better understand how a species adapts to the changes that can affect its genes. All species of great apes are threatened in the wild. With a more accurate dating of how populations have changed in relation to climate over time, we can get an idea of how species might cope with future climate change. ".
Armed with their high-performance genetic material, humans have been able to adapt to a multitude of different environments in a dazzling way. Monkeys, for their part, have not benefited from the same adaptive processes. On the other hand, the rapidity of the mutations they undergo gives the impression that they are accelerating in a kind of unexpected chase. Will they have enough time to evolve further, before the programmed extinction caused by human-induced climate change removes them from the planet's surface?
Header image: Film "Planet of the Apes - Supremacy" directed by Matt Reeves, 2017
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