April 17, 2013
Bigger Brains Indicate Hobbit Humans Evolved From Homo Erectus
Lawrence LeBlond for redOrbit.com - Your Universe Online
The hobbit human, a small-statured race that evolved separately from our own ancestor Homo erectus on an island of the Indonesian Archipelago some 50,000 years ago, has been discovered by Japanese scientists to have a bigger brain than once believed.
Hobbit humans, named after the tiny folk from JRR Tolkein's novels, are collectively known as Homo floresiensis (Man of Flores). The remains of the ancient humans were discovered on the island of Flores a decade ago (2003), unearthed from a cave by a team of Australian-Indonesian scientists.
A team of researchers from the National Museum of Science and Nature (NMSN) in Tokyo are now describing in a new paper that these ancient humans´ brains were actually quite large relatively speaking. The study strengthens the theory that H. floresiensis evolved from H. erectus.
It is believed that H. erectus, in turn, went on to evolve into our own species, H. sapiens, in Africa. The new study, published in the Proceedings of the Royal Society B (RSPB), also describes how location and environment made floresiensis look different from erectus.
Study coauthor Yousuke Kaifu told Jennifer Viegas of Discovery News that these ancient floresiensis´ were “extremely short [42 inches tall], much shorter than any healthy living humans.” He added that the legs of this race “were short relative to their arms and feet.” These features have led some scientists to assume they were of a primitive nature.
Working with lead author Daisuke Kubo and Reiko Kono, Kaifu used high-resolution micro-CT scanning to study the brain regions of the skulls of these hobbit humans. They found that the brains measured 14.4 fluid ounces (426 cc), as opposed to earlier estimates of 13.5 fluid ounces (400 cc). Even this new size is not huge by modern standards, as chimpanzees have similarly sized brains. In comparison, modern humans´ brains are 40.5 fluid ounces (1,300 cc).
The new measurements nearly confirm that H. floresiensis evolved from H. erectus. The previous size would have ruled that out because only so much shrinkage could have taken place. It is not currently clear how erectus made it to the isolated island of Flores. But their “unique evolution suggests they did not go out of the island once they got there,” said Kaifu.
He explained to Viegas that "a popular theory is that big mammals tend to reduce and small mammals tend to increase their body sizes on an isolated island because of energetic demands."
Their descendants, being cut off from the rest of the world, went through thousands of years of diminutive evolution, becoming smaller to match the availability of food on the island, the researchers theorize.
The phenomenon is known as insular dwarfism, and is well known among biologists. The island also had pygmy elephants (stegadons) at the time floresiensis thrived there.
However, the Japanese team´s theory is not the only one, reports the French news agency AFP.
One theory suggests the floresiensis species is a descendant of an even smaller, small-brained hominid known as Homo habilis. But there is yet any proof to confirm such a hypothesis. And there is no known evidence that habilis ever reached Asia.
Another theory suggests that the Flores remains are simply those of H. sapiens who suffered from some form of disability called dwarf cretinism, due to the iodine deficiency in their diet. This would result in abnormally small brain size.
However, the small hominids had the technical know-how to hunt and kill animals, use fire and wield stone tools to butcher prey, knowledge that would not have been possible among those with cretinism.
Kaifu acknowledged that the insular dwarfism theory is not a new one, but said he can support the theory with computer simulation from 20 worldwide populations of modern humans, which show that scaling down of H. floresiensis´ brain, along with the body, is entirely possible.
"New models of the brain-size reduction in the evolution of H. floresiensis... show (a) more significant contribution of scaling effect than previously claimed," claim the researchers.
Image Below: Cave where the remains of Homo floresiensis were discovered in 2003, Lian Bua, Flores, Indonesia . Credit: Rosino/Wikipedia (CC BY-SA 2.0)