Final answer:
According to the savanna hypothesis, many human traits including upright bipedalism evolved as adaptations to living in a savanna. Homo ergaster/erectus is central to this hypothesis, with reduced sexual dimorphism, increased meat consumption, and migrations out of Africa reflecting adaptability to savanna life. These evolutionary developments are believed to have been crucial for the survival and spread of these early human ancestors.
Step-by-step explanation:
What the Savannah Hypothesis Tells Us About Homo erectus/ergaster
The savanna hypothesis proposes that many human traits, including upright bipedalism, evolved as adaptations to living in a savanna habitat. This idea relates particularly to Homo erectus, sometimes referred to interchangeably as Homo ergaster, which emerged around two million years ago. These hominids featured a more modern humanoid form compared with their predecessors, displaying bipedalism almost exclusively, which according to the hypothesis, may have developed due to the open grasslands of the savanna that necessitated efficient locomotion and the ability to see over tall grass.
Homo ergaster is notable for its reduced sexual dimorphism compared to earlier hominins, such as australopithecines, which could indicate a shift towards monogamous mating systems and higher parental investment. Furthermore, Homo erectus is recognized by its successes, such as a prolonged existence, physically adapting with longer legs and increased cranial capacity, indicative of more efficient walking and hunting capabilities. Evidence suggests that these hominids began increasing their meat consumption, which is supported by the analysis of the specimen KNM ER 1808 showing a possible preference for carnivore liver, signaling a dietary shift.
Migrations of Homo ergaster out of Africa are believed to have occurred around 1.75 million years ago, leading ultimately to Homo erectus. The migration patterns signify the evolutionary spread and adaptability, where these hominids eventually populated regions as far as Java in Indonesia. These evolutionary developments and adaptations are consistent with the savanna hypothesis narrative, where environmental pressures facilitated significant changes in the physiology and behavior of early humans.