Increased brain size has been observed in individuals with autism with a wide range of cognitive functioning. The purpose of this investigation was to obtain measurements of the brain volume in a sample of nonmentally retarded autistic individuals. Magnetic resonance imaging scans from 16 nonmentally retarded individuals with autism and 19 male volunteer comparison subjects were obtained and the following structures were measured: third, fourth, and lateral ventricles and intracranial and cerebral volumes. Mean cerebral and third ventricle volumes in the autistic subjects were significantly greater than in the controls when adjusted for intracranial volume. No other significant results were found. Our finding of increased brain volume in autism is consistent with previous reports in the literature. Additional longitudinal neuroimaging and, more importantly, neuropathologic studies are warranted to provide a better understanding of the complexities underlying increased brain size in autism. (Harden, A. Y., Minshew, N. J., Mallikarjuhn, M. & Keshavan, M. S. (2001). Brain volume in autism. Journal of Child Neurology, 16(6), 421-4.)
Studies continue to be published that call attention to possible genetic causes of autism. Yet, a larger brain size in many of those that are autistic is not explored in the context of evolutionary changes over time.
Over the last 25 thousand years human brain size has grown smaller. Consider that if autistics have larger brains, they are neurological retreats to a slightly older neurological convention.
Instead of examining genes for autistic tendencies, perhaps we should be exploring the connection between evolution and ontogeny, brain size being related to maturation.
