The discovery of a tiny arm bone suggests that ancient humans known as “hobbits” became smaller after they arrived on an Indonesian island more than a million years ago, scientists reported Tuesday.
Much about the diminutive Homo floresiensis has been shrouded in mystery since the first fossils indicating their existence were discovered on the island of Flores in 2003.
These tool-using hominins are believed to have lived on the island as long as 50,000 years ago, when our own species, Homo sapiens, was already roaming the Earth, including nearby Australia.
Scientists previously estimated the hobbit was about 1.06 metres (3.5 feet) tall, based on about 60,000-year-old teeth and a jawbone found in an island cave.
But according to a study published in the journal Nature Communications, the discovery of part of an upper arm bone as well as some teeth in an open site on the island suggests that some hobbits were only about a metre tall around 700,000 years ago.
The bone was so small that the international team of researchers initially thought it belonged to a child.
Study co-author Adam Brumm, an archaeologist at Griffith University in Australia, told AFP that it is the smallest humerus fossil of an adult human ever found.
‘Truly epic’
The discovery could add fuel to a heated debate among scientists about how H. floresiensis became so small.
One side argues that hobbits — so nicknamed after the tiny heroes of J.R.R. Tolkien’s fantasy novels — descended from a tiny precursor human who arrived on Flores about a million years ago.
Others believe it was our ancestor Homo erectus, which was about our size and spread across Asia, got stuck on the island, and then evolved into the smaller H. floresiensis over the next 300,00 years.
The researchers behind the latest discovery believe it strongly supports the latter theory.
Brumm said the body size of these ancient humans was “drastically reduced, in keeping with a well-known evolutionary phenomenon known as insular dwarfism.”
Under this process, large animals shrink over time to adapt to their limited surroundings.
This tropical island was also home to other smaller mammals, including a cow-sized relative of the elephant.
The newly discovered teeth also appear to be smaller than those of Homo erectus, the researchers reported.
“If we’re right, it seems that Homo erectus was somehow able to overcome the difficult barriers of deep ocean to reach isolated islands like Flores,” Brumm said.
“We don’t know how they were doing it”, he said, adding that “accidental ‘rafting’ on tsunami debris” was a possibility.
Once these ancient humans became trapped on the island, they managed to survive for hundreds of thousands of years and evolved into “strange new forms,” Brumm said.
Mark Moore, an archaeologist at the University of New England in Australia, who was not involved in the study, said the discovery means “we can now say with confidence” that the Homo erectus theory is the more likely scenario.
Moore, who has studied stone tools used by hobbits, told AFP that this “technology did not protect our cousin species from the forces of biological evolution”.
He said the fact that hobbits have changed so much in just 300,000 years is “a reminder of the power of natural selection.”
“The evolutionary story of this group of humankind is truly epic.”
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