There is a cluster of genes that is found in Homo sapiens, but which is not found in any other ape, including Neanderthals. It turns out that the deletion of this segment (essentially, reversion of the genome to pre-Homo sapiens, at least in this section) can result in autism. They point out that
researchers determined that this structure, located at a region on chromosome 16 designated 16p11.2, first appeared in our ancestral genome about 280,000 years ago, shortly before modern humans, Homo sapiens, emerged. This organization is not seen in any other primate – not chimps, gorillas, orangutans nor the genomes of our closest relatives, the Neanderthals and Denisovans.
This certainly seems to support my contention that autism is in a real sense neotenous, at least if we consider retention “earlier traits” to be a form of neoteny. And given that it seems to result in a brain that is structurally more similar to a young child’s (2-4), it may be neotenous in the more traditional sense as well (especially if the cluster of genes in question are turned on during childhood development). While there is a great deal they do not know about this gene cluster, they determined that one gene produces a protein binds with another protein that “allows the cells to capture iron more efficiently and make it available to proteins that require it.”
“This ability to help humans to acquire and use this essential element early in life might confer a significant enough benefit to outweigh the risk of having some offspring with autism,” Eichler said.