From that starting point, he built the face in layers, working from the deep anatomy outward — the same sequence a face follows as it develops.

First, the tissue depth markers: small indicators placed at specific anatomical landmarks on the skull surface, calibrated to the known average depths of soft tissue at those points.

These averages come from studies of cadavers and from medical imaging data collected from living people.

For Neanderthals, the modern human averages must be adjusted for the specific morphological differences of the Neanderthal skull — adjustments that involve scientific judgment informed by comparative anatomy.

Second, the musculature: the muscles underlying the face determine its three-dimensional contours in ways that cannot be inferred from bone alone.