But bone does preserve traces of where muscles attached — roughened areas, ridges, depressions — and the size and configuration of those attachment sites gives information about the muscles themselves.

Gurche built up the musculature in anatomical sequence, from the deepest muscles to the most superficial.

Third, the surface features: the nose, which is not preserved in skulls and must be estimated from the shape of the nasal aperture and the nasal bones; the ears; the lips; the eyelids; the specific surface texture that gives skin its appearance.

Finally, the choices that science cannot fully constrain: skin color, hair color, hair texture and style, eye color.

For these, Gurche drew on what the genetics of other Neanderthal specimens had suggested.