What makes us different from gorillas, baboons or lemurs? Or better: what makes us similar? With the aim of answering these questions, more than one hundred scientists from 20 countries sequenced the DNA of several species of non-human primates, with surprising results for understanding the evolution of both our species and the diseases that afflict us.
We share 99% of our DNA with chimpanzees, the animal closest to humans on the primate evolutionary tree. Our last common ancestor lived seven million years ago, an amount of time that is difficult for us to imagine, but which, in species terms, is only the last chapter of the book.
In this light, several interdisciplinary teams of scientists decided to sequence the DNA of more than 800 specimens of 233 different non-human primate species, in search of what is similar to us and what is different from us. The effort was enormous: it involved a hundred scientists from 20 different countries. The result, from five different studies, was published in a special edition of the magazine ‘Science’ on 1st June.
This new genetic catalog of our first cousins represents a flood of information that would have been unthinkable to acquire a decade ago. However, thanks to the latest technological advances that make it easier to read DNA, Illumina, a leading company in genetic sequencing, was able to propose the project.
The mysteries of primate genomes
This huge database becomes a treasure. One piece of information that caught the researchers’ attention was the high genetic diversity in species that are in danger of extinction. Normally, the population decline of a species means that its genetic diversity also plummets, due to inbreeding among the surviving animals. However, most species had a diversity greater than that of humans themselves, even a population of just forty lemurs living in 12 square kilometers of Madagascar.
Katerina Guschanski, an evolutionary biologist at the University of Edinburgh, explained it this way in the article released by ‘Science’: “Population declines have been so rapid that genetics can’t catch up.” These sudden declines, which are usually due to habitat destruction by humans, then hide good news: species maintain their genetic diversity and, therefore, their hope of survival.
Another striking finding is that they observed a phenomenon called “hybridization,” something that was thought to be highly unusual, in several species. That means that different species reproduce and can give rise to new species. They found it, for example, in langurs, monkeys that live at high altitudes in China, or in Central African baboons.
In addition to being the first step to understand if this hybridization allowed them to better adapt to the environment and survive, it can also be a mirror to better understand human evolution itself, since it is considered that, millions of years ago, the same thing happened among various hominids. like Neanderthals, Denisovans and Homo sapiens, modern humans.
The genes that make us human
And it is that, although sometimes we forget, we are also animals. But how is it possible that we can send rockets into space while our evolutionary relatives don’t even know fire? That mystery, the reasons why we are so close and so far from the rest of the primates at the same time, are also hidden in our respective DNA.
In this sense, the research managed to filter 89 variants in 80 genes that make us uniquely human. That’s a reduction of about half of genetic characteristics previously thought to be unique to humans; Somehow, it brings us even closer.
Investigating these genes that differentiate us can open the door to understanding why we managed to evolve in such a different way from other primates. Some, for example, have to do with brain development, especially in the early stages.
The answers to cancer or diabetes
But when we focus on what we share and not on what differentiates us, even more useful information emerges: “Taking into account the biological proximity with non-human primates, knowledge of their genome entails a deep understanding of our own evolution as a species. , and also of the diseases associated with our own evolutionary history”.
For example, cancer. In diseases that have diverse origins, in which genetics and the environment are mixed, it is very difficult to sift through which genes and which variants we should study. One of the bets of the scientific teams in this study was to review which variants we share with the rest of the primates under one premise: if the variant is widespread in other species, it is very likely that it is not harmful.
Thus, they managed to rule out approximately 6% of the more than 4.3 million variants that had been identified. They did it, in part, thanks to an artificial intelligence algorithm trained to be able to predict which variants have harmful potential and which variants don’t, thanks to all the information sequenced from the animals.
After training it with the non-human primate database, the scientists entered the biogenetic information of more than 450,000 people, collected from the UK BioBank and donated by volunteers. Thus, they were able to identify 73% more variants that may be related to diseases such as diabetes, cancer, or heart problems.
This knowledge, increasingly refined, allows us to start new research paths for drugs or therapies that target these complex diseases.
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