but humans are the only ones who can shed tears when in distress.

I don't know about that. I have seen some animals cry, especially sea turtles when they are butchered. not a pretty sight.
Arquealogical discoveries can be a tricky business when it comes to getting to conclusions about beings that existed centuries ago and who left no record of their ways of life, other than the few artifacts that can be unearthed (including their bodies).
I find it interesting that the early findings show people buried in fetal or sleeping possition, which woud make sense with the modern notion of death as the eternal sleep/slumber, which is in turn paradoxicalgiven the scary possition modern humans are burried (who sleeps face up hands on chest or by the sides?).
Your post is fascinating because it strongly suggest that even from ancient (primitive?) times, humans seem to have assigned a certain spiritual or symbolic meaning to death and the act of burrial.
The burrial sites that impressed me the most are those of kings and emperors who had entire armies along with riches and comcubines burried with them.
Some say that was an act of belief in the after life; for me it was more of a selfish act of if-I-will-not-enjoy-this-nobody-will :)