Two million years ago, this was the face of a happy young ...

Two million years ago, this was the face of a happy young man

FROWN LINESTHATMEAN

to ours, explains Dr KristianCarlson, also of the Institute forHuman Evolution.

One of the theories ofevolution was that there was agradual increase in brain size.

With sediba, however, itappears that the frontal lobes ofthe brain were undergoing ,gradual neural reorganisation.

The frontal lobes of thebrain are the seat of somevery human traits. "Thedevelopment seen behindsediba's eyes," explainsCarlson, "is what gives us thoseunique capabilities of multi-tasking and long-termplanning."

If sediba is in our lineage,what happens next, higher upthe tree is that the brainbecomes super-sized. In thespace of the next 300000years,brain size doubles.

"What was driving thisrunaway brain?" asks Carlson.

"Was it because of language,acciahty or tool use'?"

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THEY bared their teeth notin aggression, but in thatmost warming of human

gestures, a smile.This was a 1.97-million-year-

old grin that said "I come inpeace" rather than "I am goingto bite".

Through the reconstructionof the juvenile skull of a maleAustralopithecus sediba,scientists believe this hominidwas the first to smile tocommunicate.

Last year sediba surprisedthe world when a team ofacademics unveiled themost complete and bestpreserved hominid skeletonsever found.

They were discovered atMalapa, an eroded limestonecave, in the Cradle ofHumankind, about 40kmfrom Joburg,

Now, through the use ofLI u Ing-cdgo toch nology, th

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of an early hominid.This hand belonged to the

adult female. It is about the sizeof a small human woman'shand and is the focus of one ofthe Science articles.

This was a strong hand,powerful enough to pull sedibaup into the trees, but with ahuman-like precision grip,meaning that sediba, like us,could place its thumb on eachof its fmgers.-"-We have

opened aPandora's box-,,-

It means she might havebeen a tool maker, and futureexcavations might one dayconflrm this.

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How was the site and the fossils discovered?

In early 2008,using Google Earth to spot caves in theCradle of Humankind World Heritage Site,Professor Lee Berger of Wits University renewed theexploration programme in the area. On August 1,2008,while mapping with his dog Tau, Bergerdiscovered the fossil site of Malapa. On August 15,hereturned to the site with Dr Job Kibii, Tau and histhen nine-year-old son, Matthew. Within minutes,Matthew had discovered the first piece of hominid,belonging to the Karabo MH-l skeleton. Two weekslater, Berger discovered the remains of the adultfemale skeleton MH-2 and since then, the site hasyielded one of the most remarkable records of earlyhuman origins of any site on the planet.

What does Austra/opithecus sediba mean?

Australopithecus means "southern ape", after thegenus of the Taung child, named by ProfessorRaymond Dart, also of Wits. sediba means naturalspring, fountain or wellsprirl\in Sesotho. I

Even after a year, why is there ~ill rock ah:achedto the child's skull?

,-Due to the fragility of the base of the cranrdm of thespecimen and to preserve part of the adheringmatrix for future research as technologies nnprove,the team have decided to leave the specimenpartially in rock. .

The team have been able to visualise this hiddenpart using some of the most sophisticated scanningtechnology available.

Will there be more discoveries from Malapa?

Malapa is already one of the richest early homininsites discovered, but excavations have not startedyet. When they do, before the end of the year, evenmore remarkable fmds are expected to be made atthe site.

DESIGN AND GRAPHICS: GAlL IRWIN.TEXT: COURTESY WITS UNIVERSITY

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~!Thehand\; Why is sediba's hand so

exciting'?~, • The right hand of the female MH-2 is the earliest and most completefossil hominin hand ever found. Inmost cases fossil hominin (a creaturethat is human or a human ancestor)hands prior to the Neanderthal (arecent ancestor of modern humans)are isolated bones and do not belong

to the same individual.

• This has enabled scientists not only todescribe the hand, but see how it works.

• Scientists found the hand had a longthumb compared to the fmgers - evenlonger than a modern human's thumb.

• This means that the hand was able tomake thumb-to-finger precision grips,like a human hand. This is different froman ape which has long fingers forgrasping branches or for use inlocomotion, and short thumbs, making itvery difficult for them to grasp like ahuman.

• The researchers also found, however,

that the hand was still very powerful andshows that sediba was still able to climbtrees.

So what does this say about sediba?

• The thumb-to-finger precision gripmeans that it is human-like and has anability to make stone tools.• The strong flexible hand more closelyassociated with apes means that sedibastill climbed trees.

• Scientists call this combination of manand ape features a "mosaic morphology"and argue that in comparison to the"handy man" species, Homo habilis,sediba has more features related to toolmaking.

• Sediba's hand is very different from thehand bones that were used to defme Homohabilis or the "handy man". This maysuggest that there were many differenthominins making tools with differenttypes of hand morphology around thesame time period.

Did sediba make tools'?

Excavations have not yet been conducted,so it is premature to speculate whetherany tools in direct association withAu.sediba will be found. The hand and brainmorphology suggest thatAu. sediba mayhave had the capacity to manufacture anduse complex tools.

Terms explained:

hominin: A creature that is human or ahuman ancestor.

precision grip: A grip that involves thethumb and one or more fmgers, but thepalm is not actively involved. The mostcommon one is the ability to touch theend of your thumb to the tip of yourindex fmger.Other precision grips include a pad-to-side grip between the thumb and the sideof the index flnger; such as when turninga key in a lock, or a pad-to-pad "baseball"grip, like when gripping a ball with justyour fingertips. Humans are unique intheir ability to use these grips forcefullyand for fme manoeuvring of objectswithin the hand.

The foot and ankleWhat is so important about the foot?

• Of all the evolutionary specialisations thatdefine the human species, the foot is one of themost important because it reflects a definingcharacteristic of hominins - the ability to walkupright, or bipedalism.

What is special about the ankle of Au. sediba?

• Parts of both the Karabo MH-! and the femalefossil MH-2's ankles were found. The female MH-2ankle is one of the most complete ankles everfound.

• And it was found in articulation (the bonesconnected, nearly in living anatomical

position).,

• The ankle joint is mostly human-like andthere is some evidence for a human-likearch and Achilles tendon .

• But the heel bone (calcaneal) and the lowestpart of the tibia, or shin bone (medialmalleolus), is primitive (ape-like).

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• This mosaic of features is so unusual that ifthe bones had not been found stuck together, thescientists would have put them in two differentspecies.

With these ape-like features, how do you knowthat Au. sediba was a habitual biped?

• The distal tibia or leg bone (distal tibia) contactsthe ankle bone perpendicular to the shaft of theleg bone, like that of modern hurrians.

bipedalism.

• Au. sediba, however, practised a unique form ofupright walking, not exactly like that of humans,with some degree of tree climbing.

How did you take the ankle bones apart?

• The ankle bones were taken apart "virtually"using 3D scanners, like C'I' scanners, separatingthe bones. These digital bones were then printedout so that they could be studied by scientists. Theteam did thus not damage the articulated ankle.

• This is indirectly related to the position of theknee required for upright walking.

• In addition, there is evidence of a longitudinalarch and strong Achilles tendon insertion at theback of the heel, both being requirements of

•

Homo sapiens sapiens Au sediba

MH1The pelvisWhat is special about the pelvis?

• The pelvis (hip bone) of Au. sediba is acombination of earlier hominin shapeand form, and later human shape andform.

• It is short and broad like a humanpelvis, creating more of a bowl shapethan in australopiths like Lucy.

• It retains some features of earlierhominins, particularly in the size of thejoint that links the sacrum with thevertebral column and the length of thefront part of the pelvis.

• Some parts of the pelvis areindistinguishable from the human pelvis,and it has a sigmoid shape (s-shape) alongthe top of the blades.

• It is surprising to discover such anadvanced pelvis in such a small-brainedcreature hOCfU1RO of prrwim lA lnooA OAto

the origin of the shape of the humanpelvis.

So what does this mean?

• The Obstetric Hypothesis is a scientifictheory developed over three decades agothat suggested that the evolution of thelarger brains of early Homo were thereason the human pelvis is shapeddifferently to early hominins like Lucy,which are broader, flatter and moreflaring.

• Au. sediba, with its small brain, provesthat at least in this lineage, the ObstetricHypothesis for the origins of the human-shaped pelvis is wrong, and it is thereforeprobably a hypothesis that has beenrefuted in the entire human lineage.

• The shape and form of the Au. sedibapelvis suggests that there is a need to lookat other explanations for the origins of'tho rnorlm-n polvlr shnno.

MH2