I disagree. I think there is the functional equivalent of a “social-co-processor”, what I see as the fundamental trade-off along the autism spectrum, the trading of a "theory of mind" (necessary for good and nuanced communication with neurotypically developing individuals and a “theory of reality”, (necessary for good ability at tool making and tool using).

http://daedalus2u.blogspot.com/2008/10/theory-of-mind-vs-theory-of-reality.html

Because the maternal pelvis is limited in size, the infant brain is limited at birth (still ~1% of women die per childbirth (in the wild) due to cephalopelvic disproportion). The “best” time to program the fundamental neuroanatomy of the brain is in utero, during the first trimester when the fundamental neuroanatomy of the brain is developing and when the epigenetic programming of all the neurons in the brain is occurring.

The two fundamental human traits, language and tool making and tool using both require a large brain with substantial plasticity over the individual's lifetime. But other than that they are pretty much orthogonal. I suspect there has been evolutionary pressure to optimize the neuroanatomy of the human infant brain at birth so as to optimize the neurological tasks that brain is likely to need to do over that individual's lifetime.