Sorry to be a bit stuck on this topic, but I found this while researching the astrology/autism connection and thought this might interest my readers.  It’s from an article written in 2000 by astrologer Sandra Weidner:

We are all incarnated. Any one who has looked upon the body of a deceased loved one–unless too shattered from grief to see–has the clear sensation, “he/she is no longer in this.”
We are Life which has assumed material form in order to enter a material world. For a time. For certain purposes.
The spiritual is never as limited as the material. To come here, we have to take on limitations. For one, a body is required. It represents one part of our admission ticket. The other is formed by our group as well as individual reasons for coming…. 

So, yes, we are all incarnated. Some of us, however, are more incarnated than others. Our physical bodies make it appear we are all equally here. We are not.
Autistic children are one of the groups of people who are less here. Their physical bodies are here; their identities are considerably somewhere else.
Most families of autistic children already know that. They just cannot explain why. Here, using this universal language of creation–astrology–it becomes understandable. …

Here’s where it gets really interesting:

The young of the higher mammals are born in a state of relative maturity; either immediately or shortly after birth they are small adults which not only wholly resemble adult animals but are also capable of living unaided. In order to attain a similar state of maturity the human embryo would require a pregnancy of from twenty to twenty-two months. In other words, the human child, after the nine months it spends in the womb, requires another year [italics ours] to attain the degree of maturity that characterizes the young of most other mammals at birth. 

(1)
With his “true” birth [i.e., around 21 months from conception] the human individual becomes, quite characteristically, not only an individual of his species but also a part of his group. (18) 

As the child approaches the end of the post-uterine embryonic phase [i.e., around 21 months] and becomes a human individual, not only has its body-Self, but moreover the ego has developed beyond its germinal stage and achieved a certain continuity with the child’s developing consciousness….

With the consolidation of its ego, the child gradually enters into the development of consciousness, culminating, finally in the polarization of the adult consciousness. (20)

The primal relationship [the mother/infant bond that allows the infant’s optimum development] is the ontogenetic basis for being-in-one’s-own-body, being-with-one’s-Self, being-together, and being-in-the-world.” (26)
Paraphrasing Neumann, the human infant is not fully incarnated–that is, he has a body, but not a consciousness suitable to orient and use it–until about one year after his birth. [Emphasis added.]