First, what I'm calling the Geo-Fermi Paradox - why are we the only intelligent animal on Earth?
Sure, it has advantages - but other animals would gain those advantages too. So why didn't they become intelligent (or, at least, more intelligent) too?
Sure, there was climate-change in Africa that rewarded adaptivity - but why didn't all animals in the region become intelligent (or, at least, more intelligent)?
This article has a good argument for bipelalism (due to forests becoming plains). And an interesting argument for stone throwing (and not available to bipeds like ostriches and emus).
Throwing rewards spatial reasoning, providing an evolutionary pressure It's not clear to me that this would lead to intelligence - but maybe it did. (OTOH bonobos, chimpanzees, gorillas, orang-utans, and capuchins throw too https://wikipedia.org/wiki/Projectile_use_by_non-human_organ...).