40,000 years? Man migrated out of Africa 700,000 years ago and something tells me he was a true hunter at that time.
Up until what Anthropologists call the GLF, it's more likely that our ancestors were more scavengers than hunters. whatever hunting they actually did was most likely sporatic and confined to smaller game.
With the development of true language man could develop and communicate complex hunting stratagies, devise more complex weapons and tools (there's no evidence that man had developed composite weapons, ie., wooden spears with stone spearheads, up til this point).
The ability to track and take down large game allowed man more freedom of movement and motived him to start following the herds.
This, along with the access to hides and the ability to tailor clothes to his needs made it possible for him to expand his range over a much greater area, hence, as I've said,
extensive migration. It's true that migration had been going on for practically the entire existence of humanoids, but at this point his range expanded more extensively and more quickly than in the entirety of his existence up until that point put together.
(I tried to find something on the GLf on google but all I got was info on the Great Leap Forward in China in the '50s
)