So I spend a lot of time thinking about human evolutionary origins, or at least in the context of the morphological novelties we possess that set us apart from other species. Fitting, as this is essentially what my research focuses on, albeit in beetles.
One thing that just baffles me is the patchy distribution of hair on our bodies. There are many theories that try to explain this phenomena, but I think most of them are largely incomplete. P.E. Wheeler puts the onus on thermal regulation coupled with bipedality, Markus Rantala claims it had to do with a fitness advantage against ectoparasites, and Elaine Morgan even claims it was an adaptation to aquatic environments! Mine may seem like a fatuous criticism, and that is a valid complaint, but my criticism really hinges on what I consider an outstanding problem in evolutionary biology.