What does Australopithecus sediba mean?
Australopithecus means southern ape, after the genus of the Taung child, named by Prof. Raymond Dart, also from the University of the Witwatersrand, Johannesburg.
Sediba means natural spring, fountain or wellspring in Sotho, an appropriate name for a species that might be the point from which the genus Homo arises.
As the hominids were also found preserved in an ancient underground lake or spring, the name also relates to their place of discovery.
What is a hominid/hominin?
A hominid is a member of the taxonomic family that includes humans, chimpanzees, gorillas and their extinct ancestors. Hominins are members of the human branch after the human lineage split from that of chimpanzees, and thus include living humans and extinct human ancestors, such as the Australopiths. Hominins are characterised by bipedal locomotion, although this may not have been the case for the very earliest members of the group, and relatively small canine teeth. Later members of this group (those in the genus, Homo) are characterised by larger brains than those of living apes like chimpanzees, bonobos, gorillas, orangutans and gibbons.
How were the fossils dated?
They were dated using a variety of methods including Uranium-Lead, palaeomagnetic and faunal dating systems. Cosmogenic dating was used to interpret the landscape formation and to determine the depth of the cave at the time of deposition.
How were the individuals preserved?
The site where the fossils were discovered is technically the infill of a de-roofed cave that was about 50 metres underground 1.9 million years ago. The individuals appear to have fallen, along with other animals, into a deep cave, landing on the floor for a few days or weeks. The bodies were then washed into an underground lake or pool, probably pushed there by a large rainstorm.
They did not travel far, maybe a few metres, where they were solidified, as if thrown into quick setting concrete. The rock they are preserved in is called calcified clastic sediment. Over the past 1.9 million years the land has eroded to expose the fossil bearing sediments.
Did they die at the same time, or was it a catastrophe?
The hominin skeletons were found with the bones either in partial articulation or in close anatomical association, which suggests that both bodies were only partially decomposed at the time of deposition in the lower chamber. This further suggests that they died very close in time to each other, either at the same time, or hours, days or weeks apart.
How old is the child?
The juvenile is around 10 13 years old in human developmental terms. He was probably a bit younger in actual age (perhaps as young as eight or nine or so) as the species is likely to have matured faster than humans. The age estimate is based on modern human standards by which the eruption stages of the teeth are evaluated, and the degree of development of the growth centres of the bones are studied.
How old is the female skeleton?
Based on the extreme wear of her teeth, she is probably at least in her late twenties or early thirties.
Did she have children?
It is likely that a female Australopith of her age would have had children.
How do you know the child is a male?
There are features of the face that help us determine that the child is a male. The muscles of the child are larger than that of the other skeleton, even though it is a child. There are also features of the pelvis that we can use to determine that it is a male.
How does this find relate to Lucy?
Australopithecus sediba is approximately a million years younger than Lucy. Some scientists feel that Lucys species, Au. Afarensis, gave rise to Au. africanus and in the paper, the team is suggesting that Au. africanus or something similar, gave rise to Au. Sediba.
How do you know that it is a new species?
The team compared the skeletons with all the remains of fossil hominids that have been discovered and in many ways they are absolutely unique from any fossil species found.
Why is this not the genus Homo?
The fossils have an overall body plan that is like that of other Australopiths they have small brains, relatively small bodies and long and seemingly powerful arms. They do have some features in the skull and pelvis that are found in members of the genus Homo but not in other Australopiths. However, given the small brains and Australopith-like upper body, the team felt that keeping this species in the genus Australopithecus was the conservative thing to do.
What about Homo habilis?
Our study indicates that Australopithecus sediba may be a better ancestor of Homo erectus and it may certainly help to clear up some of this muddle in the middle.
Why is there still rock attached to the childs skull?
Due to the fragility of the base of the cranium of the specimen and to preserve part of the adhering matrix for future research, the team has decided to leave the specimen partially in rock. The team has been able to visualise this hidden part using scanning technology.
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12-04-2010 om 20:23
geschreven door Tsjok45