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In the Liang Bua cave, on the island of Flores (Indonesia), the remains of a new species were discovered in 2004, Homo floresiensis, nicknamed the ‘hobbit’ because of its small stature.
No one has since been able to recover the DNA from their fossils, but a group of researchers has created a tool to find archaic genetic sequences in modern DNA. Its objective, to know if these ‘hobbits’ had genetic links with the modern pygmies of the Island of Flores.
The technique was developed in the laboratory of Joshua Akey, Professor of Ecology and Evolutionary Biology at the Lewis-Sigler Institute for Integrative Genomics at Princeton University (USA). The results are published in the journal Science.
Fossil evidence indicates that H. floresiensis were significantly smaller than modern Flores pygmies. Floresiensis also differ from H. sapiens and H. erectus on their wrists and feet, likely due to the need to climb trees to evade Komodo dragons, according to Serena Tucci, an associate postdoctoral researcher in Akey's lab.
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“In your genome and in mine there are genes that we inherit from Neanderthals. Some modern humans inherited genes from Denisovans (another extinct species of humans) that we can verify because we have their genetic information. But if you want to look for another species, like Floresiensis, there is nothing to compare, so we had to develop another method: 'we paint' chunks of the genome based on the source. We scan the genome and look for pieces from different species: Neanderthals, Denisovans or strangers, ”says Tucci.
The researchers used this technique on the genomes of 32 modern pygmies living in a village near the Liang Bua cave.
“They have a large Neanderthal genome, a bit of Denisovan –something we expected because we knew there was a migration going from Oceania to Flores–, so there was a certain shared ancestry of these populations,” the authors emphasize.
Richard "Ed" Green, associate professor of biomolecular engineering at the University of California, Santa Cruz (USA) and co-author of the work argues: "If there were any possibility of knowing genetically the 'hobbit' from the genomes of existing humans, would have appeared. But we don't see it. There is no indication of 'hobbit' gene flow in people living today. "
Flores Island: home to dwarf elephants and giant Komodo dragons
However, scientists they did find evolutionary changes associated with diet and short stature. Tucci and his team analyzed the genomes of the Flores pygmies by comparing them with the height-associated genes of Europeans and found a high frequency of genetic variants associated with short stature.
"It sounds like a boring result, but it's actually quite significant," Green adds.
“It states that these genetic variants were present in a common ancestor of the Europeans and the Flores pygmies. They reduced their size by selection, acting on this permanent variation already present in the population, so there is little need for the genes of an archaic hominid to explain their small stature. '
In the time of H. floresiensis, Flores was home to dwarf elephants, giant Komodo dragons, and giant birds and rats. All of them left bones in the Liang Bua cave.
"Islands are very special places for evolution," says Tucci. "This process of insular dwarfism resulted in smaller mammals, such as hippos and elephants, and smaller humans."
Their results show that insular dwarfism arose independently at least twice on Flores Island: first in H. floresiensis and again in modern pygmies.
Dramatic changes in size in isolated animals on the islands are a common phenomenon, often attributed to limited food resources and freedom from predators. In general, large species tend to get smaller and small species tend to grow on islands.
“This is really intriguing, because it means that, from an evolutionary point of view, we are not that special. Humans are like other mammals, we are subject to the same processes, "he concludes.
The Flores pygmy genome it also showed evidence of selection in genes for enzymes involved in fatty acid metabolism, called FADS.
These genes have been associated with dietary adaptations in other fish-eating populations, including Eskimos in Greenland.
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