The classic Neanderthals, who lived between about 70,000 and 30,000 years ago, shared a number of special characteristics. Like any biological population, Neanderthals also showed variation in the degree to which those characteristics were expressed. Generally, they were powerfully built, short and stocky, with the lower parts of their arms and legs short in relation to the upper parts, as in modern peoples who live in cold environments. Neanderthal skulls were distinctive, housing brains even larger on average than those of modem humans, a feature that may have had more to do with their large, heavy bodies than with superior intelligence. Seen from behind, Neanderthal skulls look almost spherical, but from the side they are long and flattened often with a bulging back.

The Neanderthal face, dominated by a projecting and full nose, differed clearly from the faces of other hominids; the middle parts appear to be pulled forward (or the sides pulled back), resulting in a rather streamlined face shape. This peculiarity may have been related to the greater importance (in cultural activities as well as food processing) of the front teeth, which are large and part of a row of teeth that lies well forward in the head; it may reflect a reduction in importance of certain jaw muscles operating at the sides of the face; or it may reflect an adaptation to cold. Whether it results from any or all of these three factors or from other, undiscovered causes, this midfacial projection is so characteristic that it unfailingly identifies a Neanderthal to the trained eye. Neanderthal teeth are much more difficult to characterize: the front teeth are large, with strong roots, but the back teeth may be relatively small. This feature may have been an adaptation to cope with heavy tooth wear