Are these two sentences grammatically correct?
If yes, why? and what is the difference? Thank you in advance.

If early humans had not eaten meats, they wouldn’t have evolved into smart humans.
If early humans did not eat meat, they could not evolve into smart humans.

Question

Are these two sentences grammatically correct?
If yes, why? and what is the difference? Thank you in advance.

If early humans had not eaten meats, they wouldn’t have evolved into smart humans.
If early humans did not eat meat, they could not evolve into smart humans.

Answer

Both sentences say the same thing , but from different point of view .
had not > the event did not happen before/at a certain time which the writer had in his mind ( emphasis on the action in relation to a time in the past)
did not > the event just never happened ( emphasis is on the action itself)

Answer

The first sentence is correct, as you are discussing the past.