Final answer:
The four characteristics of the skull that differ with race include the shape of the skull, the presence or absence of a supraorbital ridge, the nasal index proportions, and the degree of prognathism.
Step-by-step explanation:
There are four characteristics of the skull that can differ with race. These characteristics are as follows: Shape of the skull; absence or presence of a supraorbital ridge (brow ridge); proportions of the nasal index (a measure that reflects the width of the nasal opening relative to the height of the nasal bridge); and prognathism (placement and projection of the jaw).
The nasal index is particularly significant as it varies widely among different racial groups, with a lower nasal index indicating a narrower nose and a higher index indicating a broader nose. Factors such as environment and genetic heritage play a role in shaping these features, though it's important to note that such racial categorizations are somewhat simplistic, given the wide diversity within any population.