According to scripture Adam could speak with God from the very day he was created (See Genesis chapter 2).
Dr. Jack Cuozzo's book "Buried Alive - The Startling Truth about Neanderthal Man" shows that Neanderthal man was fully human and that their odd facial features are the result of living to the great ages described in the book of Genesis.
So as he aged, Adam began to look like a Neanderthal, but could talk with God from the very first day he was Created (Day 6).
Yet those who believe in Evolution claim that Neanderthal lacked the anatomy that would enable them to speak.
Dr. Cuozzo responds to these claims:
In addition to that, since Laitman came out with his
theory,the Kebara Neanderthal was found in Israel with a normal human
hyoid bone, the floating bone in the throat where the infra and supra-hyoid musculature attach. This suggested normal speech too, however the cartilage was not
on the hyoid which couldn't survive very long anyway. I don't
know why this argument persists for so long except for the fact that there are so many out there who would have Neanderthals be less than human. Dr. Mann is not one of them and I believe he said so in the debate."
"I was prepared on the night of the debate to show an overhead that displayed
a cephalometric x-ray of one of my female 12 yr. old patients
with a very flat cranial base (143) and the Gibraltar I Neanderthal female cephalometric x-ray with a cranial base of 140 degrees. My patient had less cranial flexion than the Neanderthal. The Neanderthals were not supposed
to speak according to J. Laitman* because of this flat cranial
base which would mean a very high position of the larynx (voice box), he thought. Well, my
patient spoke very well and so did all of my other patients near the 140 degree mark.
*note: Laitman expanded on the work of Phillip Lieberman and Ed Crelin.
Speech in Neanderthal man is one more piece of evidence showing they were fully human.