Jun 8, 2007
Neanderthals likely did not possess the cognitive complexities of modern humans and, as a result, probably did not suffer from schizophrenia and certain other mental disorders, according to a new theory.
The theory proposes that language, creativity and many mental diseases are linked, due to the fact that they may originate in the neocortex, as well as the densely cell-packed cortex, located towards the top of the brain. These brain regions appear to mature and develop more slowly than other areas.
Although there are conflicting claims about possible Neanderthal creative abilities, no direct evidence supports that this extinct human species or subspecies possessed full-fledged grammatical language. Neanderthals had large brains, but researchers believe their mental skills matured rapidly, closing the door to disorders associated with the cortex.
Modern humans, on the other hand, must take the bad with the good.
"In a nutshell, I feel that the extremely long maturation time of our brains — greater than 20 years — allows them to develop many and various capabilities, such as language and schizophrenia," H. Lee Seldon, the theory’s author, told Discovery News.
Seldon, a senior lecturer and an expert on health informatics at Monash University in Australia, added, "Also, because of the long maturation time, environmental factors have more time to exert modifying influences on the final outcome."
He explained that if our brains stopped being modified at age 5, then "we would not have such well-developed language and we would likely not have so much schizophrenia."
Seldon, whose work has been accepted for publication in the journal Medical Hypotheses, believes three basic factors led to human language, creativity and certain mental disorders.
The first factor is a sex-linked gene that "steers brain development towards anatomical and functional asymmetry." A second genetic factor allows us to process fatty acids and produce large quantities of brain membranes, essentially permitting the growth of a big brain.
While Neanderthals probably possessed the first factor and some version of the second, the third genetic determinant appears to be unique to modern humans. Seldon believes it is a gene that influences cortical growth and stretching.
It also delays the end of brain growth until the third decade of life. The developing white matter in the cortex literally winds up expanding parts of our brain like a balloon, according to the hypothesis.
Timothy Crow, a leading brain researcher and a professor of psychiatry at the University of Oxford, said he agrees with the speculation about Neanderthals and shares the view that the cortex of modern humans is ballooned later in life.
"We have evidence that is well explained by it and it is important. It gives us a bridge between structure and function," he told Discovery News.
Crow, however, does not think a change in fatty acids separated Neanderthals from humans and led to our more advanced cognitive skills. Instead, he thinks a gene pair, named Protocadherin XY, "is a determinant of cerebral asymmetry and is responsible for the transition to modern Homo sapiens."
Both Crow and Seldon hope future related studies might one day reveal more about the origin of the human brain and its unique disorders. Such research could lead to better treatments for schizophrenia, autism and other brain problems.