So we have seen footage of mammoths in the nylithic era, will mammoths survive the nylithic era if not hunted down too much? 
and can you use mammoths to create units normally recuiring elephants such as the war elephant of the carthegian empire? 
and will for the unit be stronger in its natrual biome if you can, so cartaghian war elephants made from mammoths are stronger in colder biomes, while carthagian war elephants made out of elephant maybe being stronger in their respective biome?