Is there a time limit on earthbound spirits?

please dont get me wrong, i definitely believe dogs and cats horses monkeys..., other loving animal definitely have can be spirits and have souls.

Maybe there is? or maybe prehistoric human life was so simplistic they had no ties to earth. almost non intelligent animal like. theorizing gould possibly land me in trouble. so what if early humans where not capable of feeling a tie to earth, meaning their main purpose was to make it long enough to mate in an animalistic nature in other words:just survive. or perhaps, the lack of energy source ie power lines, telephone lines prevented prehistoric beings from developing in ectoplasmic energy... see i told you theory could likely land me into trouble lol

Humans has been on this earth for thousands of years . So has any one seen a caveman? If not why not, what is your opinion. This may sound a little funny but think about it. I have never seen or talked to anyone that has witnessed a prehistoric human.