Not sure if this has been proposed before, but it occurred to me a few years ago that reduction in limb and body hair would be highly advantageous for an upright biped starting to work with fire. A chimp- or gorilla-style pelage could catch fire near ground level and result in nasty burns at face height. As far as I know the times of origin of these two derived conditions haven't yet been shown to be different. Any thoughts?
Evolution would favor those not stupid enough to be that careless...