Final answer:
Facial approximation and tissue depth markers are the two techniques needed to reconstruct a face from a skull.
Step-by-step explanation:
The two techniques needed to reconstruct a face from a skull are facial approximation and tissue depth markers. Facial approximation involves creating a model or drawing of the face based on the skull's features, while tissue depth markers are used to determine the thickness of the soft tissues that would cover the skull. These techniques help forensic anthropologists and forensic artists recreate the appearance of an individual based on their skeletal remains.