MONDAY, Sept. 24 (HealthDay News) -- Humans' larger brain size in comparison to chimpanzees begins in the womb, a new study finds.
Japanese researchers tracked and compared growth in human and chimpanzee fetuses and found notable differences. In both species, the brain grows increasingly quickly in the womb at first.
But after 22 weeks' gestation, brain growth in chimpanzees starts to level off while human brain growth continues to accelerate for at least another two months, according to the study in the Sept. 25 issue of the journal Current Biology.
Normal gestation time is 38 weeks for humans and 33 to 34 weeks for chimpanzees.
The researchers used 3D ultrasound imaging of two pregnant chimpanzees from about 14 to 34 weeks of gestation and compared them to images of developing human fetuses.
"Nobody knew how early these differences between human and chimp brains emerged," study author Satoshi Hirata, of Kyoto University, said in a journal news release, which calls this the first study to measure chimps' brain development in the womb.
In a previous study, the same team compared brain development in chimps and humans from the age of 6 months to 6 years.
"Elucidating these differences in the developmental patterns of brain structure between humans and great apes will provide important clues to understand the remarkable enlargement of the modern human brain and humans' sophisticated behavior," study co-author Tomoko Sakai said in the news release.
The U.S. National Institute of Neurological Disorders and Stroke explains brain basics.
SOURCE: Current Biology, news release, Sept. 24, 2012
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