Final answer:
Ardipithecus ramidus, known as Ardi, has key features such as bipedalism, small upper arm bones, thin dental enamel, reduced canines, and an opposable big toe suggesting a lifestyle adapted for both terrestrial and arboreal locomotion. The reduced canine size is linked to social evolution towards less aggressive behaviors.
Step-by-step explanation:
The fossil of Ardipithecus ramidus, or “Ardi”, provides insight into early hominin characteristics. Found in Ethiopia in 1992 and dating back to the Pliocene era (≈ 4.4 MYA), Ardi is significant for understanding human evolution. One notable feature is the forward position of the foramen magnum, indicating bipedalism. Moreover, Ardi's relatively small upper arm bones suggest that its arms were not primary weight-bearing structures during locomotion. The species exhibits thin dental enamel, indicative of a divergent dietary habit compared to other contemporary primates. The presence of a reduced canine and an opposable big toe further distinguish Ardi from other early hominids, reflecting adaptations for bipedality on the ground and potential quadrupedal movement in trees. This versatility is supported by its discovery in heavily forested environments. In terms of social evolution, it is hypothesized that the reduction of canine size correlates with less aggressive behaviors and female preference for less aggressive males.