Skulls of ancient hippos shed light on origin of Hobbit’s brain

May 9th, 2009 - 1:09 pm ICT by ANI  

Washington, May 9 (ANI): Ancient Madagascan hippos have shed light on the origins of the small brain of the 1-metre-tall human, known as the ‘hobbit’.

By examining the skulls of extinct Madagascan hippos, scientists at the Natural History Museum discovered that dwarfed mammals on islands evolved much smaller brains in relation to their body size.

So, Homo floresiensis may have had a tiny brain because it lived on an island.

This is something which has been at the heart of the debate of the Hobbit’s origins, whose remains were uncovered on the Indonesian island of Flores in 2003.

The team suggests that the hobbit became a dwarf after its Homo erectus ancestor became isolated on the large island of Madagascar many years ago.

“The discovery of a small fossil human from the island of Flores with normal facial proportions but a brain the size of chimpanzee has baffled scientists,” explained Natural History Museum palaeontologist, Dr Eleanor Weston, who led the research.

“It could be that its skull is that of a dwarfed mammal living on an island. Looking at pygmy hippos in Madagascar, which possess exceptionally small brains for their size, suggests that the ‘hobbit’ was a dwarf resulting from its H. erectus ancestors being isolated on the island in the past,” Weston added.

The team studied species of extinct Madagascan hippos and their mainland ancestor, the large common hippopotamus.

One of the specimens used, from the Museum’s mammal collection, was a nearly 3000-year-old dwarf hippo skull belonging to the extinct Hippopotamus madagascariensis.

Hippo brain-body scaling trends were calculated from the relationship of brain to skull size.

“We found that the brain sizes of extinct dwarf hippos were still up to 30 percent smaller than you would expect by scaling down their mainland African ancestor to the dwarf’s body size,” explained Dr Weston.

“If the hippo model is applied to a typical H. erectus ancestor, the resulting brain capacity is comparable to that of H. floresiensis,” he added.

The brain of Homo floresiensis is the smallest yet known for any hominid.

According to the researchers, it may be advantageous to the survival of animals that become isolated on islands with unique environments, not only to become dwarfs, but also to reduce the size of their brain.

“Whatever the explanation for the tiny brain of floresiensis relative to its body size, it’s likely that the fact that it lived on an island played a significant part in its evolution,” concluded Dr Weston. (ANI)

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