This whole concept is really fuzzy for two reasons.

first, there's no dividing line between us and our human-like ancestors.

second, this depends on the precise moment life begins. Quite a few people claim to believe that human life begins at conception - if that's the case, in order to be consistent, they should count life starting from conception, which would at least double the total historical human population (due to natural miscarriages, not just abortions).