Exam 10: Early Hominid Origins and Evolution: The Roots of Humanity

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Ever since Darwin's time,scientists have generated hypotheses to explain the presumed advantage conferred to early hominids who adopted a habitual bipedal way of moving around the landscape.Since this is a singular event among primates,and in fact among placental mammals,these hypotheses have proven difficult to test.Nonetheless,several plausible ideas have been proposed,including:
•Bipedalism is an energetically efficient way of moving over longer distances,for example between patches of trees in an increasingly open paleoenvironment.•Bipedalism would have allowed hominids to see over tall savanna grasses and thus to identify predators,competitors,water sources,fruiting trees,etc.,at a safe distance.•Compared to quadrupedalism,bipedalism would have provided a thermoregulatory advantage,since less body surface would have been exposed to direct sunlight.•Using the lower limbs exclusively for locomotion would have freed the hands for carrying things like food,babies,tools,etc.•Bipedalism,like the giraffe's long neck,would have allowed individuals to reach food items out of a quadruped's reach.•Standing on two legs may have made early hominids appear bigger and more threatening,discouraging predators and quadrupedal competitors alike.