![]() In contrast, the foramen magnum in nonhuman apes is positioned posteriorly on the skull and faces backward, corresponding to an inclined vertebral column. In other words, it appeared to Dart as if the specimen had been bipedal. This was a critical observation because an anteriorly positioned foramen magnum suggests that the vertebral column was vertically oriented and positioned directly beneath the skull, as in humans. ![]() Most importantly, its brain was small but appeared to be reorganized so that its spinal cord exited the cranial cavity through a hole (the foramen magnum) that was positioned farther forward on the skull than is typical in apes. However, its canine was slightly smaller and its face was slightly less projecting than one might have expected of a juvenile ape at a similar stage of development. The specimen’s morphology was broadly ape-like, and it was clearly a juvenile because it still possessed some of its milk (deciduous) teeth. They were diverse, geographically widespread, and anatomically derived, they lived through periods of pronounced climate change, and their story dominates the narrative of human evolution for millions of years. ![]() Regardless, australopiths had a rich evolutionary history deserving of study independent of questions about our direct ancestry. However, Homo is almost certainly descended from an australopith ancestor, so at least one or some australopiths belong directly to the human lineage. They also are distinguished by their lack of derived features typically associated with the genus Homo, such as a large brain, a broad complement of adaptations for manual dexterity, and advanced tool use. Dietary adaptations clearly played an important role in shaping their evolutionary history. In particular, they are bipedal apes that, to a greater or lesser extent, exhibit enlarged molar and premolar teeth (postcanine megadontia) and other associated modifications to their feeding apparatuses. Rather, they are grouped together informally because nearly all share a similar adaptive grade (i.e., they have similar adaptations). ![]() Formerly known as the australopithecines, they are not a “natural” group, in that they do not represent all of the descendants of a single common ancestor (i.e., they are not a “clade”). The australopiths are a group of early hominins (humans and their close extinct relatives) that lived in Africa between approximately 4.1 and 1.4 million years ago. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |