Modern Flores Island pygmies show no genetic link to extinct “hobbits” – ScienceDaily


Two populations of pygmies on the same tropical island. One died out tens of thousands of years ago; the other still lives there. Are they related?

It’s a simple question that took years to answer.

As no one was able to recover the DNA from the fossils of Homo floresiensis (nicknamed the “hobbit”), the researchers had to create a tool to find archaic genetic sequences in modern DNA.

The technique was developed by scientists in the lab of Joshua Akey, professor of ecology and evolutionary biology, and the Lewis-Sigler Institute for Integrative Genomics at Princeton University.

“In your genome – and mine – there are genes that we inherited from Neanderthals,” said Serena Tucci, postdoctoral research associate at Akey’s lab. “Some modern humans inherited genes from Denisovans [another extinct species of humans], which we can verify because we have genetic information from Denisovans.

“But if you want to look for another species, like Floresiensis, we have nothing to compare, so we had to develop another method: we “paint” pieces of the genome according to the source. We scan the genome and look for pieces that come from different species – Neanderthals, Denisovans, or something unknown. “

She used this technique with the genomes of 32 modern pygmies living in a village near Liang Bua Cave on Flores Island in Indonesia, where H. floresiensis fossils were discovered in 2004.

“They definitely have a lot of Neanderthals,” said Tucci, who was the first author of an Aug. 3 article in the newspaper. Science who detailed their findings. “They have a bit of Denisovan. We expected that, because we knew there was a migration from Oceania to Flores, so there was a common ancestry of these populations.”

But there were no chromosomal “pieces” of unknown origin.

“If there had been a chance to genetically know the hobbit from existing human genomes, it would have been,” said Richard “Ed” Green, associate professor of biomolecular engineering at the University of California. Santa Cruz (UCSC) and a corresponding author on the paper. “But we don’t see it. There is no indication of gene flow from the hobbit to people living today.”

Researchers have found evolutionary changes associated with diet and short stature. Height is very inherited, and geneticists have identified many genes with variants related to either being taller or shorter. Tucci and his colleagues analyzed the pygmy genomes of Flores against genes associated with height identified in Europeans, and they found a high frequency of genetic variants associated with short stature.

“It sounds like a boring result, but it’s actually quite significant,” Green said. “This means that these genetic variants were present in a common ancestor of Europeans and Flores’ pygmies. Stature.”

Flores’ pygmy genome has also shown evidence of selection in genes for enzymes involved in fatty acid metabolism, called FADS (fatty acid desaturase) enzymes. These genes have been associated with dietary adaptations in other fish-eating populations, including the Inuit of Greenland.

Fossil evidence indicates H. floresiensis was significantly smaller than modern Flores pygmies, standing about 3.5 feet tall (106 centimeters, shorter than the average American kindergarten), while modern pygmies averaged about 15 inches taller (145 centimeters). Floresiensis also differed from H. sapiens and H. erectus in their wrists and feet, possibly due to the need to climb trees to escape the Komodo dragons, Tucci said.

Dramatic size changes in animals isolated on the islands are a common occurrence, often attributed to limited food resources and the absence of predators. In general, large species tend to get smaller and small species tend to get bigger on islands. At the time of H. floresiensis, Flores was home to dwarf elephants, giant Komodo dragons, giant birds and giant rats, all of which left bones in the Liang Bua cave.

“Islands are very special places of evolution,” said Tucci. “This process, island dwarfism, has given rise to smaller mammals, like hippos and elephants, and smaller humans.”

Their results show that island dwarfism has appeared independently at least twice on the island of Flores, she said, first in H. floresiensis and again among modern pygmies.

“It’s really intriguing because it means that in evolution we are not that special,” she said. “Humans are like other mammals; we go through the same processes. “


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