OUR EARLY ANCESTORS

[image:http://i.imgur.com/UhAJUHM.png?1] Our story begins as long as '''6 million years ago''', when the East African savannah was still a densely wooded forest. These earliest Hominids may mark the beginning of the Hominin branch, the point at which our ancestors diverged from the apes. These are the earliest apes for which there is some evidence of a habitually bipedal lifestyle. [image:http://i.imgur.com/hMCtUoo.png?2] '''1) Orrorin tugenensis''' Fossils include fragmentary arm and thigh bones, lower jaws, and teeth and were discovered in deposits that are about 6 million years old. The limb bones are about 1.5 times larger than those of Lucy, and suggest that it was about the size of a female chimpanzee. Its finders have claimed that Orrorin was a human ancestor adapted to both bipedalism and tree climbing, and that the australopithecines are an offshoot. Given the fragmentary nature of the remains, other scientists have been sceptical of these claims so far. Some scientists have argued that this may be a gorilla ancestor (an early branch for the apes that later lead to today’s apes). [image:http://i.imgur.com/39WPLjM.png?1] '''2) Ardipithecus ramidus''' Originally dated at 4.4 million years, but has since been discovered to far back as 5.8 million years. Most remains are skull fragments. Indirect evidence suggests that it was possibly bipedal, and that some individuals were about 122 cm (4'0") tall. The teeth are intermediate between those of earlier apes and A. afarensis, but one baby tooth is very primitive, resembling a chimpanzee tooth more than any other known hominid tooth. Other fossils found with ramidus indicate that it may have been a forest dweller. This may cause revision of current theories about why hominids became bipedal, which often link bipedalism with a move to a savannah environment. '''Key Ideas''': These Early Hominids were essentially '''chimpanzee-like animals''' that have begun to show some human characteristics, namely bipedal locomotion (movement) and the shape / arrangement of their teeth. '''To what degree these Hominids were bipedal is debated'''. We know they lived in a wooded forest environment and indirect evidence suggests that they were at least partially bipedal.