A series of five papers based on new evidence pertaining to various aspects of the anatomy of the species Australopithecus sediba (announced in April 2010 by Berger et al), will appear in the prestigious journal Science on Friday, 9 September 2011.
The papers will reveal new, important elements attributed to the two type skeletons, which will include an analysis of the most complete hand ever described in an early hominin, the most complete undistorted pelvis (hip bone) ever discovered, the highest resolution and most accurate scan of an early human ancestors brain ever made, new pieces of the foot and ankle skeleton, and one of the most accurate, if not the most accurate dates ever achieved for an early hominin site in Africa.
According to Prof. Lee Berger, a Reader in Evolution at the Institute for Human Evolution at the University of the Witwatersrand in Johannesburg, South Africa, Au. sediba demonstrates a surprisingly unique combination of features, never before seen in an early human ancestor.
"The fossils demonstrate a surprisingly advanced but small brain, a very evolved hand with a long thumb like a humans, a very modern pelvis, but a foot and ankle shape never seen in any hominin species that combines features of both apes and humans in one anatomical package. The many very advanced features found in the brain and body, and the earlier date make it possibly the best candidate ancestor for our genus, the genus Homo, more so than previous discoveries such as Homo habilis ."
Since its discovery in August 2008, the site of Malapa has yielded well over 220 bones of early hominins representing more than five individuals, including the remains of babies, juveniles and adults.
Given the open access policy of the team, sediba is already one of the best studied hominin species yet discovered.
The team studying these fossils is one of the largest ever assembled in the history of archaeology or palaeontology. With more than 80 scientists, students and technicians from across the globe involved in the study, the teams expertise range from geologists, computer specialists, functional morphologists and anatomists, to physicists.
This is one of the largest collection of scientific papers ever produced by an African based team or University, on a single subject to be published in a journal of this impact level.
View a video at www.wits.ac.za/ihe
FREQUENTLY ASKED QUESTIONS
Section A – The Fossils
Prof. Lee Berger, Reader in Human Evolution at the University of the Witwatersrand, Johannesburg, and Sediba project leader, responds to some common questions pertaining to Au. sediba .
Since its discovery in August 2008, the site of Malapa has yielded well over 220 bones of early hominins representing more than five individuals, including the remains of babies, juveniles and adults. The evidence published in Science is based on two individuals from the site – MH1 and MH2.
How were the individuals preserved?
The site where the fossils were discovered is technically the infill of a de-roofed cave that was about 30 to 50 metres underground just under two million years ago. The individuals appear to have fallen, along with other animals, into a deep cave, landing up 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 into the rock, as if thrown into quick setting concrete. The rock they are preserved in is called calcified clastic sediment. Over the past 2 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 the 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. Other animals have been found with them - equally complete - including sabre-toothed cats, hyenas, antelopes, mice, birds and even snails. There is also plant material that has been found.
Is there organic preservation like plant remains or skin?
The preservation at Malapa is excellent and there are certainly organic remains preserved like plant remains. There are some indications that even the soft tissues of animals are preserved, including possibly skin. This material is presently under study by a worldwide based team of experts, who are attempting to prove or disprove the existence of such important material, and to develop methods to study specimens that have never been found before in the early hominin record.
How old are the children you have found?
How old is the female skeleton?
Did she have children?
If she did have children, would the child be large-brained or small-brained?
How do you know the child is a male?
Are they related to each other?
Section B – The Brain
Dr Kristian Carlson at the University of the Witwatersrand, Johannesburg, responds to some common questions pertaining to Au. sediba .
What does the study of the brain show?
What is so special about the brain scan?
Where is the synchrotron scanner that was used?
How does a brain endocast form?
Section C – The Hand
Dr Tracy Kivell is a Researcher in the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology in Germany. She provides an overview of the paper pertaining to an analysis of the hand of Au. sediba .
Overview
This paper describes the earliest, most complete fossil hominin hand post-dating the appearance of stone tools in the archaeological record. Almost all other fossil hominin hand bones prior to Neandertals are isolated bones that are not anatomically associated (i.e., do not belong to the same individual) and are not clearly affiliated with specific hominin species.
The Au. sediba hand thus allows us for the first time prior to Neandertals to evaluate the functional morphology of the hand overall, rather than just isolated bones. In our paper, we investigate the presence of several features that have been associated with human-like precision grip and the ability to make stone tools. Au. sediba has many of these features, including a relatively long thumb compared to the fingers – longer than even that of modern humans – that would facilitate thumb-to-finger precision grips. Importantly, Au. sediba has more features related to tool-making than the OH 7 hand that was used to originally define the "handy man" species, Homo habilis .
However, Au. sediba also retains morphology that suggests the hand was still capable of powerful flexion needed for climbing in trees. Taken together, we conclude that mosaic morphology of Au. sediba had a hand still used for arboreal locomotion but was also capable of human-like precision grips. In comparision with the hand of Homo habilis , Au. sediba makes a better candidate for an early tool-making hominin hand and the condition from which the later Homo hand evolved.
Is this the first, and most complete hand of an early hominin ever described?
Why is the hand unique?
However, the Au. sediba hand is still primitive in many ways compared to modern humans, and the team does not suggest that Au. sediba was the only hominin around 2 million years ago capable of making tools. For example, the Au. sediba hand morphology is very different from the hand bones that were used to define the first tool-maker, Homo habilis or the "handy man". This may suggest that there were many different hominins making tools with different types of hand morphology around the same time period.
Compared to the hand of Au. afarensis – Lucy's species – Au. sediba has fingers that are shorter (thus, a proportionately longer thumb) and less curved, suggesting that Au. sediba was not moving around in the trees as much as Lucy. Au. sediba has broader finger tips, stronger muscles of the thumb and a more human-like wrist that also suggest it had better manipulative abilities than Lucy and her kin.
What is a precision grip?
A precision grip is a grip that involves the thumb and one or more fingers, but the palm is not actively involved. There are several different types of precision grips, but the most common one people think of is the ability to touch the end of your thumb to the tip of your index finger. Other precision grips include a pad-to-side grip between the thumb and the side of the index finger, such as when turning a key in a lock, or a pad-to-pad "baseball" grip, like when gripping a ball with just your fingertips. Other primates are capable of some precision grips but humans are unique in their ability to use these grips forcefully and for fine manoeuvring of objects within the hand. Au. sediba would have, without a doubt, had an excellent precision grip.
Does Au. sediba imply that Homo habilis was not a tool-maker?
When a direct comparison between the bones preserved in Au. sediba and the OH 7 "handy man" hand bones is made, their anatomy is very different. The OH 7 hand appears to have a derived large, robust thumb and very broad finger tips, while the Au. sediba thumb is gracile and the fingers tips are not quite as broad.
In contrast, OH 7 still has fingers that are strongly curved and the wrist bones are more like those of African apes, while Au. sediba is more derived or human-like in these features. This difference in morphology implies two (though not necessarily mutually exclusive) scenarios: (1) that both species are capable of making tools but that they do this with different anatomy or (2) that the OH 7 hand does not in fact belong to Homo habilis , but is instead the hand of another early hominin species. Either way, it is likely that many hominin species were capable of making stone tools given that stone tools appear in the archaeological record long before either Au. sediba or Homo habilis are known to have lived.
However, the paucity of complete hand bones in the fossil record and our poor understanding of how the human hand functions and what morphology is necessary to make tools has limited our ability to determine exactly which species made tools and when and how tool-making first evolved. Au. sediba has shed new light on these questions.
Have you found tools on sites?
Excavations have not yet been conducted, so it is premature to speculate whether any tools in direct association with Au. sediba will be found. The hand and brain morphology suggest that Au. sediba may have had the capacity to manufacture and use complex tools.
Section D – The Pelvis
Dr Job Kibii at the University of the Witwatersrand, Johannesburg, responds to some common questions pertaining to Au. sediba .
What is special about the pelvis?
The pelvis (hip bone) of Au. sediba is a combination of earlier hominin shape and form and later human shape and form. It is short and broad like a human pelvis, creating more of a bowl shape than in an australopiths like Lucy. It still retains some features of earlier hominins, particularly in the size of the joint that links the sacrum with the vertebral column and the length of the front part of the pelvis. Parts of the pelvis are indistinguishable from that of humans, and it has a sigmoid shape (s-shape) along the top of the blades. It is surprising to discover such an advanced pelvis in such a small-brained creature because of previous ideas as to the origin of the shape of the human pelvis.
How does the pelvis of Au. sediba relate to the Obstetric Hypothesis?
Section E – The Foot & Ankle
Dr Bernhard Zipfel at the University of the Witwatersrand, Johannesburg, responds to some common questions pertaining to Au. sediba .
What is so important about the foot?
What is special about the ankle of Au. sediba ?
The ankle joint is mostly human-like in form and inferred function, and there is some evidence for a human-like arch and Achilles tendon. However, a surprising find is that Au. sediba is ape-like in possessing a more gracile calcaneal (heel) body and a more robust medial malleolus (the lowest part of the tibia, or shin bone) than expected. This suggests that Au. sediba may have practiced a unique form of bipedalism, and would have almost certainly climbed trees.
It is also surprising that with parts of the heel being more primitive than earlier hominins like Lucy, it may mean that Au. sediba did not descend from this lineage. No ankle has ever been described with so many primitive and advanced features in one complex, and if the bones had not been found stuck together, the team may have described them as belonging to different species.
With these ape like features, how do you know that Au. sediba was a habitual biped?
How did you take the ankle bones apart?
Section F - Dating of the fossils
Dr Robyn Pickering, lead author on the paper pertaining to dating, responds to some common questions pertaining to Au. sediba .
The new date of the fossils is (1.977 to 1.98 million years old) is one of the most accurate dates ever achieved in the early hominin record.
How were the fossils dated?
Cosmogenic dating was also used to interpret the landscape formation and to determine the depth of the cave at the time of deposition.
Why can't you date the fossil themselves?
What is a flowstone/speleothem?
A speleothem is a technical term used to describe any type of rock forming in a cave, so stalagmites, stalactites and flowstones are all types of speleothems.
What is uranium-lead dating?
What is Palaeo-Magnetic dating?
What happens during a palaeo-magnetic reversal event like the one seen in the rocks of Malapa?
Section G – The Discovery
Prof. Lee Berger, Reader in Human Evolution at the University of the Witwatersrand, Johannesburg, responds to some common questions pertaining to Au. sediba .
How was the site and the fossils discovered?
In early 2008, using Google Earth to spot caves in the Cradle of Humankind World Heritage Site, Berger renewed the exploration programme in the area. With the assistance of new technology available, Berger discovered, over a few months, more than 600 caves and more than three dozen new fossil sites in one of the most explored areas on the planet.
On the 1st of August 2008, while mapping with his dog Tau, Berger discovered the fossil site of Malapa. On the 15th of August he returned to the site with Dr Job Kibii, Tau and his then 9- year-old son, Matthew. Within minutes, Matthew had discovered the first piece of hominid, belonging to the MH-1 skeleton. Two weeks later, Berger discovered the remains of the adult female skeleton MH-2 and since then, the site has yielded one of the most remarkable records of early human origins of any site on the planet.
What does Australopithecus sediba mean?
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?
How does this find relate to Lucy?
Has the new species named last year been accepted by the scientific community?
So why is this not the genus Homo?
What about Homo habilis ?
Will there be more discoveries from Malapa?
CONTACT DETAILS
For more information or to download the media pack, including images, podcasts and video material, visit www.wits.ac.za/sediba once the embargo is lifted.
For interviews with any of the authors from the University of the Witwatersrand, Johannesburg (aka Wits University) including: Prof. Lee Berger (project leader), Dr Kris Carlson (brain), Dr Bernhard Zipfel (foot and ankle) and Dr Job Kibii (pelvis) contact Shirona Patel, Head: Communications, on +27 11 717 1019 or +27 83 362 1995 or email Shirona.Patel@wits.ac.za
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