Final answer:
The consistency of discrete skeletal traits within geographic regions from Homo erectus to present-day supports the savanna hypothesis, which postulates that many human traits like upright bipedalism evolved due to adaptations to a grassland ecosystem.
Step-by-step explanation:
The presence of discrete skeletal traits that are consistent within geographic regions from Homo erectus to the present supports the hypothesis that many human traits such as upright bipedalism evolved as adaptations to a savanna habitat. This concept is known as the savanna hypothesis. This hypothesis suggests that the early hominins adapted to an environment with fewer trees and a more open grassland ecosystem, which led to bipedal walking as a means of efficient locomotion under these conditions. The skeletal evidence that supports this hypothesis shows minimally changing morphological adaptations in human ancestors that persisted in similar environments throughout time.