I believe he needs actual dna and not just bone but if he did then he would probably be able to but early homo species woudnt be the best choice for any situation, not for fighting, intelligence, speed, none of that

But fossils have DNA in them.

Fossils contain DNA. It literally belongs to the species. The Omnitrix doesn't need much to scan DNA as it scan have of human DNA .

He would only be able to turn into something thats less then 6.8 million years old, after that dna expires, so no dinosaurs

Im not really sure if ben would be able to scan dna from bones, the nemetrix can do it but not sure about the omnitrix

the nemetrix is like a cheap copy of the omnitrix if nemetrix can, the omnitrix could