Final answer:
Ardipithecus kadabba and Ardipithecus ramidus are early hominins with significant contributions to our understanding of human evolution, such as the development of reduced canine size and bipedality, providing insights into the evolution of human-like traits.
Step-by-step explanation:
The species Ardipithecus kadabba is a significant early hominin and plays an important role in our understanding of human evolution. This species, alongside its close relation Ardipithecus ramidus, is noted for its reduced canine size and possible bipedalism. A. kadabba fossils date back to approximately 5.6 million years ago (MYA), making it one of the earliest hominids. The discovery of these early hominins in Ethiopia alongside others such as Australopithecus afarensis and Australopithecus africanus, provides valuable insight into the evolution of bipedality and other human-like traits.
An important finding noted in a study published in the Proceedings of the National Academy of Sciences indicated that the canine sexual dimorphism in Ardipithecus ramidus, which lived around 4.4 MYA, was nearly human-like. This discovery suggests a significant evolutionary step towards reduced aggression and possibly a social structure similar to modern humans. The forward position of the foramen magnum in the skeletal remains found in Ardipithecus ramidus indicates bipedality, supporting the theory that this trait evolved early in human ancestry.