...it is generally agreed that a modern skull should present a relatively small face tucked under the vault that is relatively short and high, a relatively vertical forehead, parietal enlargement, a relatively rounded occiput, a flexed cranial base, a canine fossa, an occipital protuberance in the occipital bone and mental eminence or chin. Most descriptions of modern H. sapiens would also include skeletal gracility as characterizing the group.But read the Modernity mess as well by Wolpoff & Caspari.
Lahr, M.M. & Wright, R.S.V. (1996) The question of robusticity and the relationship between cranial size and shape in Homo sapiens. Journal of Human Evolution, 31: 157-191.