The Japan Times, June 13, 1998
First humans less brainy than previous estimates
WASHINGTON (Reuters) Early humans may not have been as big-brained, and therefore not as intelligent, as was earlier thought, researchers said Thursday.
CAT scans showed the brain of an early pre-human who died 2.6 million to 2.8 million years ago, nicknamed "Mr. Ples," was much smaller than earlier estimated.
Writing in the journal Science, they said the skulls of other early humans were probably smaller than had been believed, as well.
"Some estimates of brain size in early hominids may be too high," Glenn Conroy, a professor of anatomy and physiology at Washington University in St. Louis, said in a statement. "This paper implies that something is very wrong with previous interpretations of early hominid brain capacity."
Mr. Ples was found in 1989 in South Africa. He was an australopithecine, one of the early precursors or relatives of humans known as a hominid
The skull is partly preserved, but big parts on one side are missing, so scientists had to estimate the capacity — a pointer to brain size and thus intelligence. They reckoned it could hold more than 600 cc, or about two and a half cups of water.
"Such a large brain would be quite extraordinary because all of the other Australopithecus africanus brains are in the mid-400 cc range," Conroy said.
Modern humans have a brain that is about 1200 cc.
Conroy's team had developed a more exact technique for measuring skulls, using computer-assisted tomography, or CAT scans. This allows scientists to make a three-dimensional image of the human body.
Their tests showed Mr. Ples' skull had a capacity of about 515 cc.
"While this is still the largest known brain for A. africanus, it is nowhere near what has been bandied about by paleoanthropologists," Conroy said.
Conroy ran the same test on another skull he keeps on his desk. It had been estimated to be 440 cc, but the CAT scans showed it was only 370 cc.
"I was shocked because there was supposed to be a quantitative leap in brain size that distinguished early hominids from apes, yet 370 cc is the size of a chimpanzee brain," Conroy said.