New Evidence Points to the Flores 'Hobbit' as a Dwarf Species

A new analysis by Stephen Montgomery and Nicholas Mundy at the University of Cambridge is adding credence to the suggestion that the extinct Homo floresiensis was a dwarf species. And the new clue, they say, comes from the teeth of the world's tiniest monkey.

Ever since the discovery of a H. floresiensis fossil on the island of Flores in 2003, scientists have speculated that its miniaturized characteristics were the result of insular dwarfism — a form of speciation (and one not uncommon to other species on the island). These so-called Hobbits measured only three feet (one meter) in height and weighed about 70 pounds (32 kilograms).

New Evidence Points to the Flores 'Hobbit' as a Dwarf Species

Not everyone buys the dwarf theory, however, mainly on account of the size of its brain and teeth — measurements that are proportionally much smaller than what would be expected in a dwarf species. Some have even gone so far as to say that the Flores specimen was simply a diseased human.

But Montgomery and Mundy, after studying the teeth of pygmy marmosets (Callithrixpygmaea), noticed that they've also got unusually small teeth. And pygmy marmosets, as the team confirmed, evolved from larger ancestors. They're a dwarf species.

Writing in New Scientist, Colin Barras explains more:

So why the small teeth? The evolution of a dwarf species usually involves shortening the length of pregnancy or infancy, but recently it has been suggested that there might be a more unusual route: pregnancy length stays the same but the growth of the fetus slows down. This might influence brain and tooth size as these develop early.

Montgomery and Mundy found that the pygmy marmoset's pregnancy and infancy are similar in length to their evolutionarily close, larger relations. This suggests they took the unconventional route to small stature.

"If H. floresiensis is a dwarf, one of the controversies has been whether it fits with previous patterns of dwarfism," says Montgomery. The new analysis suggests it may fit with what is seen in pygmy marmosets.

Check out the study at Journal of Evolutionary Biology.

Image: Top: Susan Hayes; Marmoset: Jared Hobbs/All Canada Photos/Corbis.