So, I know that Homo sapiens sapiens survived quite a few demographic bottlenecks in the process of spreading across the planet; if there's one thing demographic bottlenecks tend to do, is to reduce the genetic diversity of the population by quite a lot, with a corresponding decline in the range of "available" phenotypes.

Today, humanity is one of the least diverse species on the planet, but reading a modern take on the planetary romance genre while watching TierZoo and PBS Eons videos made me wonder, how diverse could we have realistically gotten, without resorting to the kind of selective breeding practices that allowed us to turn wolves into chihuahuas?