But they do support the idea that the primates have their own communication system that involves a complex combination of facial, body, and hand gestures, along with grunting and other vocalizations, the researchers say. In most people, the structure, a slender inch-long piece of tissue called theplanum temporale, is larger in the left side of the brain than the right. Since this area is involved in the processing and comprehension of speech sounds and sign language, scientists concluded 30 years ago that an enlarged plenum temporale in the left hemisphere was required for language and may haveevolved for this purpose. Until now, no other animal was shown to have the same asymmetry in this brain region, located at the side of the head and connected to the ears. It shows the dangers of concentrating on brain centers and areas, he said, and supports recent research showing that language is widely distributed in the brain and probably evolved from novel connections rather than from new structures.
Language evolution remains a profound mystery.
Sometime within the last twomillion years, two-legged primates, or hominids, developed the ability to talk with words, a dazzlingly difficult skill, said Dr. Terrence Deacon, a biologicalanthropologist at Boston University and McLean Hospital at Harvard Medical School. One can imagine the brain undergoing important reorganizations that underlie the ability to argue, cajole, complain and pontificate. In the late 1960's, scientists were strongly influenced by the idea that bigger is better and that evolutionary pressures would lead to obvious structural changes in the human brain, Dr. Deacon said. If they could find unique bits of human brain architecture, they concluded, it might explain language. A study conducted in 1968 seemed to confirm this view, Dr. Deacon said.