New australopithecine described

by Greg Mayer

Lee Berger of the University of the Witwatersrand and several colleagues will be describing a new species of Australopithecus, A. sediba, from 1.78 to 1.95 million-year-old deposits in South Africa, in tomorrow’s issue of Science. The issue will also have a geological article on the find by Paul H.G.M. Dirks of James Cook University, Queensland, and colleagues, and a news item, all available now at Science‘s website (plus a podcast and video). The description is based on two partial skeletons, including a well preserved juvenile skull, most of the right arm and shoulder girdle, parts of the hip and leg, and various other bits.

Skull of juvenile Australopithecus sediba. Image from University of the Witwatersrand.

The new species has a long arm, but the pelvis and leg indicate that it was bipedal (i.e. it could both climb and walk upright). The general evolutionary conclusion the authors draw is the mosaic nature of the origin of Homo features: some Homo-like characters evolved before others, e.g. bipedality preceding cranial enlargement. They find specific features linking the new species to Homo, and posit it to be intermediate between earlier australopithecines and Homo:

The age and overall morphology of Au. sediba imply that it is most likely descended from Au. africanus, and appears more derived toward Homo than do Au. afarensis, Au. garhi, and Au. africanus.

Something I rather liked about the paper is that it is quite data rich, having tables of comparison of traits and measurements of the new find and several other fossil hominids. Such data-richness is unusual for papers in Science, which prefers short papers, with data often being relegated to electronic appendices or other papers; the Berger et al. paper is an unusual ten pages long.

The news has already reached media websites (e.g. the New York Times, the BBC and the Telegraph). Unlike the case of Darwinius masillae, however, in which premature press coverage, which included the name and its diagnostic characters, and web posting of the description, led to questions about the proper authorship and publication of the name, the authors and journalists in this case have done everything right. The news accounts are appearing coincident with the name being published (i.e. printed on paper), not prior to its publication. (The newspaper pieces linked to above are online now, but they won’t be published in the sense of the International Code of Zoological Nomenclature until tomorrow, when the scientific paper itself will be published.) There will thus be no questions about the publication of the name; the authors have made sure that, as the ICZN recommends, Australopithecus sediba is “self-evidently published within the meaning of the Code” (ICZN, Rec. 8B)

17 Comments

  1. Posted April 8, 2010 at 12:10 pm | Permalink

    Must…resist….obvious….oh hell, I’ll just say it:

    Damn! Two more gaps!

  2. KP
    Posted April 8, 2010 at 12:32 pm | Permalink

    I just skimmed the paper and it was quite interesting. Those fossils are getting more transitional than ever — i.e. a more direct ancestor of Homo may have been found. An australopithecine with some erectus-like postcranial features, but, for example, a cranial capacity of 420. Will Answers in Genesis call this one an “ape” or a “human?”

    My favorite bit vis-a-vis preempting the predictable creationist canard that an ancestor can’t be found more recently in the fossil record than a descendant: “The discovery of a <1.95-million-year-old (16)australopith that is potentially ancestral to Homo is seemingly at odds with the recovery of older fossils attributed to the latter genus (5) or of approximately contemporaneous fossils attributable to H. erectus (6, 30). However, it is unlikely that Malapa represents either the earliest or the latest temporal appearance of Au. sediba, nor does it encompass the geographical expanse that the species once occupied. We hypothesize that Au. sediba was derived via cladogenesis from Au. africanus (≈3.0 to 2.4 Ma), a taxon whose first and last appearance dates are also uncertain (31). The possibility that Au. sediba split from Au. africanus before the earliest appearance of Homo cannot be discounted."

    • Posted April 8, 2010 at 3:03 pm | Permalink

      Forgive my ignorance, but are they dating this find based on the surrounding material that it was found in?

      • Torbjörn Larsson, OM
        Posted April 8, 2010 at 4:02 pm | Permalink

        Yes. I just browsed, but they seem to use both radiometric and paleomagnetic (if that is the term) data to box the layers in. Those are fluvial, but rapid burial is posed based on the close relationships of the found parts. You may be the judge.

  3. NewEnglandBob
    Posted April 8, 2010 at 12:32 pm | Permalink

    This is not just a potential gap filler, It is potentially a bridge from Australopithecus to Homo.

  4. Posted April 8, 2010 at 2:22 pm | Permalink

    OK, why is Russell Blackford popping up as a possible link to this australopithecine find?

    Seriously, this is really neat and potentially hugely important.

    • Artikcat
      Posted April 8, 2010 at 3:48 pm | Permalink

      It woule explain plenty. Refreshing:-) In the meantime run for cover Moscow, Good luck in the aftermath.

      • Posted April 8, 2010 at 5:46 pm | Permalink

        I’m a great admirer of Russell and his writing (which I think he knows). I was just wondering why his name pops up twice as possibly related links.

        • Artikcat
          Posted April 8, 2010 at 5:54 pm | Permalink

          Come along now Dr Moscow, didnt imply anything “bad”.. we all have something like 99 % australo genes, right..? Proud of our ancestry. At least me, maybe others dont like to be reminded. All is cool..

          • articulett
            Posted April 8, 2010 at 8:38 pm | Permalink

            I wondered about his name in the links too– Russel is Australian, not Austalopithecean (though I can see how an automated generator might get confused). –Plus, I’m quite sure his cranial capacity is much more than 420.

            • articulett
              Posted April 8, 2010 at 8:40 pm | Permalink

              (‘good save, eh Moscow?– I’ll put it on your tab.)

            • Posted April 9, 2010 at 12:37 am | Permalink

              Ah, that must be it. “Austral -”

              And call me Ray.

  5. MadScientist
    Posted April 8, 2010 at 3:44 pm | Permalink

    Any links to their press releases? The press have got the story all wrong of course – it’s as if they have creationist editors who look at what’s written and make sure there can be nothing sensible written.

  6. Torbjörn Larsson, OM
    Posted April 8, 2010 at 3:59 pm | Permalink

    Intriguing. The S3 figure cladistics show A. sediba splitting H. habilis/H. rudolfensis and H. erectus. I would love to see an analysis with later species used such as the H.habilis related H. floresienis. Alas, Berger is claiming that the later doesn’t exist.

    Also, it means that A. sediba is (near) the root of Homo.

    Tim White doesn’t believe it is: “The characteristics shared by A. sediba and Homo are few and could be due to normal variation among australopithecines or because of the boy’s juvenile status, argues Tim White,” But the juvenile status as nearly fully grown is shored up by analysis from both human and ape side, and they use many characters in the analysis.

    In the end, the authors opt out too: “The team thought long and hard about putting the fossils into Homo but decided that given the small brain and other features, the hominin was “australopithecine-grade,” says team member Steven Churchill”.

    Aaargh! I really don’t like when earlier theories corrupt data analysis.

  7. James F
    Posted April 8, 2010 at 5:17 pm | Permalink

    On a report on NPR today, they noted that there are two more skeletons at the site. Exciting!

  8. This Supid Lamb
    Posted April 8, 2010 at 6:40 pm | Permalink

    very nice post!

  9. Microraptor
    Posted April 11, 2010 at 9:01 am | Permalink

    I saw this in the local newspaper.

    I was quite pleased that the article contained a quote from Dr Berger explaining how the term “missing link” was inaccurate and no longer in use after the paper used the headline “New Missing Link Found.”


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