Hendrik Poinar speaks with VERY from his home in Ontario (Canada), just before Current Biology magazine published his work in which, together with a team of experts, he shows the first complete genome sequenced of the woolly mammoth, a feat that previously seemed of Science fiction. Poinar, director of the Center for Ancient DNA at McMaster University in Hamilton, Ontario, is enthusiastic about rescuing genetic material from extinct species: “This science has come a long way in the last ten years . I participated as a student in the first wave and now I work in the second. I feel like my grandfather, even though I am 44 years old, ”he jokes.
At first, specializing in the recovery of fossil genes was a very limited discipline: “At that time I believed that we would never be able to sequence the entire DNA of an extinct organism. Most, some loose fragments. But now everything has changed ”, confesses Poinar. The test, the cited article in Current Biology , with two complete genomic sequences. The first belongs to a woolly mammoth that lived 4,300 years ago on Wrangel Island in the Arctic Ocean. He was one of the last survivors of his kind. The other genome is from a 44,800-year-old specimen, found almost intact in the frozen soil – permafrost – of Siberia.
New sequencing techniques, capable of processing large amounts of DNA in a short time, have had a lot to do with it. According to Poinar, we are entering the third phase of this discipline, which allows us to read in the genes the evolutionary history of the creatures that dominated the Earth and that finally became extinct. Our expert is fascinated by the evolutionary history of the woolly mammoth, which intersects with that of humans, as both species emerged in Africa six million years ago. Elephants migrated to colonize Central Asia, diversify into northern Siberia, and reach Europe. At the same time, they crossed the land bridge across the Bering Strait that linked Eurasia with North America.
In this process, several proboscidean species emerged that we can include in the genus Mammuthus . In addition to the woolly ( Mammuthus primigenius ), in North and Central America another very large species emerged, although not so hairy, known as the Columbian or Columbia mammoth ( Mammuthus columbi ), whose DNA is also being analyzed by Poinar. His team is investigating the changes in the genome that made it possible for a species originally adapted to a hot and dry climate such as the African to become one capable of living in freezing climates , even in the Arctic, for 600,000 years. And with the addition that these regions also suffered profound climatic changes, glaciations and interglacial periods, in which they went from extreme cold to heat.
The Columbian mammoth was almost twice as large as the woolly one. It lived in savannahs with a continental climate in Mexico and the United States, while the woolly was adapted to frigid weather. There could not be two more distinct proboscis. However, analysis of the DNA housed in the mitochondria – the powerhouses of the cell – shows, according to Poinar, that the two species met in time and space, when a severe cooling pushed the woolly mammoths to regions further al south. “There, the females of this species selected the Columbian males to mate with . Before we thought that they were very different species, separated by a million years, but now we know that they were able to mix and maintain their genetic diversity ”.
Genes also write the epitaph for disappearing creatures. What caused the extinction of mammoths, despite their great adaptability? How is it that in the last 11,000 years – a very short time on a geological scale – in New Zealand, Australia, North America, Asia and Europe, between 80% and 90% of large mammals have become extinct? Was it due to the weather, man, or both?
“The problem is that in these 11,000 years both factors coincide: there was a climate change and human beings also arrived in all those areas.” Those who believe that we are responsible are based on animal fossils in which there are marks of spears and other stone utensils. Instead, those who see climate change as the most likely causes of megamammal decline and disappearance argue that the theory of Homo sapiens extinction cannot be generalized on the basis of a few findings.
The idea of bringing an extinct species back to life found a home in the mind of his son Hendrick, who has been a privileged witness to the technological evolution experienced for two decades in the sequencing of genetic material. “I grew up hearing stories of insects trapped in amber that could have their DNA cloned. I remember the conversations my father had with Crichton. In the end, we became scientific advisers to Spielberg’s film. Do you remember the scene where a person comes out drilling fossil amber? Initially I was going to interpret it, but finally they chose an actor, with good criteria ”.
Poinar junior believes that the information that can be extracted from DNA has limitations. Jurassic Park remains a fiction – and may never become reality – for a number of reasons. It is feasible to imagine that traces of dinosaur blood could have remained in the stomachs of the mosquitoes that bit them, always in soft areas, around the eyes or on the nasal mucosa. It is also possible that the red blood cells of dinosaurs could contain genetic nuclei, as it occurs with birds, with which they are related, unlike in mammals, whose red blood cells are enucleated. What is not feasible at all is that the DNA of that blood can be rescued, since so far there are no indications that make us think that it could be preserved for millions of years without degrading . That’s the problem. Even fossil proteins, which do not contain genetic information, do not last beyond a million years.
Therefore, the rescue of extinct species would have to be placed in much more recent times, and not 65 million years ago. But Poinar’s genetic study of the woolly mammoth would have stunned skeptics less than a decade ago. Have the gaps been filled with elephant genetic material? What is its degree of precision? “Basically we have the complete coding genome sequence – a coding region of DNA is one that makes biological sense, since it contains the information to make proteins. What we don’t have are the repeated sequences. The architecture is still missing ”.
