Many treasures compete for attention, but there is one sample, kept in a small plywood box, that deserves especial interest: the Swanscombe skull. Found near Gravesend last century, it is made up of three pieces of the brain case of a 400,000-year-old female and is one of only half-a-dozen bits of skeleton that can be traced to men and women who lived in Britain before the end of the last ice age. Human remains do not get more precious than this. However, the Swanscombe find is important for another, crucial reason: the skull is that of a Neanderthal, that race...