Flores Island Pygmies (Extant and Extinct) are the Result of Island Dwarfism

Homo floresiensis ('Flores Man') is possibly an extinct species in the genus Homo. It lived from 60,000 to 100,000 years ago.
The remains of an individual that would have stood about 1.10 m in height were discovered in 2003 in the Liang Bua cave on the Indonesian island of Flores. Partial skeletons of nine other individuals have been recovered, including one complete skull. These remains have been the subject of intense research and debate whether they represent a distinct species from modern humans or whether they were the result of insular dwarfism.

Both modern man (Homo sapiens), the Neanderthals (Homo neanderthalensis ) and the Denisovans (Homo sapiens denisova) share a common ancestor (Homo heidelbergensis). From all three species we have been able to collect their DNA. Modern humans all have bits of DNA of the Neanderthals and the Denisovans burried within their own DNA.
[Skulls of Homo floresiensis and Homo sapiens]
If Homo floresiensis was a seperate species one would expect to find bits of DNA that do not match the three related species. The problem is that scientists haven't been able to extract DNA from the fossilized remains of Homo floresiensis.

A modern pygmy population evolved short stature independently of the extinct Homo floresiensis species that lived on the same island tens of thousands of years earlier, a study reports[1]. Are they related? Scientists took DNA samples from 32 of these villagers and studied their DNA.

"They definitely have a lot of Neanderthal," said Serena Tucci, lead author. "They have a little bit of Denisovan. We expected that, because we knew there was some migration that went from Oceania to Flores, so there was some shared ancestry of these populations."

But there were no chromosomal 'bits' of unknown origins. While it is not certain that Homo floresiensis and the modern pygmies from flores are related, it is certain is that there's is no indication of gene flow from the Homo floresiensis into people living today.

Tucci and her colleagues analyzed the Flores pygmy genomes with respect to height-associated genes identified in Europeans, and they found a high frequency of genetic variants associated with short stature.
Fossil evidence indicates Homo floresiensis was significantly smaller than the modern Flores pygmies, standing about 106 centimeters, while modern pygmies average about 145 centimeters. Homo Floresiensis also differed from Homo sapiens in their wrists and feet, probably due to the need to climb trees to evade Komodo dragons, said Tucci.

Dramatic size changes in animals isolated on islands is a common phenomenon, often attributed to limited food resources and absense of predators. In general, large species tend to get smaller and small species tend to get larger on islands. At the time of Homo 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.

Their results show that insular dwarfism arose independently at least twice on Flores Island, she said, first in Homo floresiensis and again in the modern pygmies.

[1] Tucci et al: Evolutionary history and adaptation of a human pygmy population of Flores Island, Indonesia in Science – 2018

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