>>12255778>indistinguishable from a human
probably wouldn't work at all. sorta reminds me of the creationist misunderstanding that we come from chimps, whereas we just have a not too distant(compared to other species) common ancestor.
So we branched off from chimps entirely a while ago. From that point you can't really crossover again unless the two species can produce fertile offspring with each other and we're way too different for that already.
All that said you might get a human-like chimp if you tried, it just wouldn't be indistinguishable.
Probably wouldn't even take that long(in evolutionary timescales), apparently the development for human cognitive abilities was surprisingly short(though for an exact number I would have to look it up, without just pulling something out of my ass).
The biggest obstacle, aside from it just being a pain in the ass to breed fucking chimps, would be that it's what to select for. As we don't know what evolutionary pressures made humans develop our cognitive abilities in the first place.