In the United States, anencephaly occurs in about 1 out of every 10,000 births. There are several forms of this condition, wherein the forebrain is absent. The forebrain is host to most of the higher functional areas in the mammalian brain. In the most extreme case of anencephaly, the so called
holo-form, only the brain stem remains.
MacLean's model of the brain, the term
brain stem is used interchangeably with the term reptilian brain, to designate the most primitive parts of the central nervous system. Many are taught this model.
("An anencephalic newborn", wikimedia, author: Almazi, license: public domain, DOR 27/09/2012)
From my layman's perspective I can't help but notice a reptilian likeness of the anencephalic newborn. Whilst it goes without saying that correlation doesn't equal causation, I would like to know what is known so far about the cause of this condition to yield this particular morphology (as seen in the picture)?
Perhaps someone (eventually) has even some evodevo insight to share as well?