New fossil hominid find to be released this week

Just the other day a friend of mine in Austin asked, rather skeptically, "where's the missing link," referring to human evolution. I tried to explain, not only do we have an embarrassment of riches when it comes to "missing links" in human evolution between our earliest ancestors and anatomically modern humans, they are even found in the precise temporal order predicted by evolutionary biology. We even have footprints! The one on the far left courtesy of Nature Magazine comes from a transitional hominid that trudged through a muddy East African plain almost four million years ago. The one right next to it courtesy of NASA was made by a much later hominid model on the Sea of Tranquility. That's a sobering illustration that we've come a long way, baby!

Well, speak of the devil, now we may have one more 'missing link'. The field of human and primate origins is all a'twitter, literally, about a new set of fossil hominids which reportedly includes a nearly complete skeleton and bones from several indviduals:

Scientists say the two million-year-old fossilised skeleton is from a previously unknown type of hominid, the evolutionary branch of primates that led to humans. The new species could be an intermediate stage between ape-like hominids and the first species of advanced humans, Homo habilis.

Recall that a few months ago, anthropologists released new details about Ardipithecus ramidus or Ardi, a possible link between apes that walked mostly on four limbs and the earliest known habitually bipedal hominids.

   Chimp                                               Ardipithecus                                     A. Afarensis (Lucy)       

Shown above, the skeleton of a modern chimp included just for comparison (Chimps have been evolving for millions of years as well), a front and side view of Ardi, and Lucy aka Australopithecus afarensis. For scale, Ardi is just over one-meter or a little over three feet in height. But a tantalizing handful of scraps and lots of speculation are all that linked Lucy's kind to the first, more recognizable modern human ancestor Homo habilis. The scientific name is Latin for handy man, so named because H. habilis is the first hominid found in close proximity to the earliest flaked stone tools, an example of which are shown left in schematic.

In brief, two specimens of Ardi appear in the fossil record at 5.6 and 4.4 million years ago respectively. Lucy and other gracile austalopithicines show up between 4 and 3 million. H. habilis  lived about two-million years ago, and is followed in the fossil record by Homo ergaster which thrived between 1.8 and 1.2 million years ago. Ergaster apparently sired a number of robust variations such as the far-flung, classic Homo erectus and later, Homo heidelbergensis. The latter, or again something very much like it, is believed to have given rise both to the well known European Neandertals beginning about 400,000 years ago and anatomically modern humans in Africa which first appear around 200,000 years ago.

That's a lot of links, and I've left out several others, enough that any first year physical anthropology student reading this is probably rolling their eyes at my brevity right about now. The term missing link is actually an anachronism anyway. It originates from a time over fifty years ago when anthropologist were looking for a large brained slouching "ape-man" that it turns out didn't exist. The great finds of the 60s and 70s demonstrated that upright bipedal locomation came before the brain begin swelling. And no matter how many gaps are filled, each new find only creates two more gaps on either side of it.

Of course the media is using the old missing link and 'scientists stunned' mantra. I'd like to note for the record scientists wouldn't be "stunned" by a link between apish-like Lucy and a more human like habilis. Nor would it rewrite our understanding of human evo. Quite the contrary, such a transitional critter would have had to exist if gracile australopithicines like Lucy evolved into something like H. habilis. Scientists "thrilled to uncover fossil hominid that the prevailing consensus on human evolution predicted' would be more like it. The discoverers are keeping the new find[s] under tight wraps for now. But if, as preliminary reports indicate, it links gracile Australopithecus like Lucy to H. habilis,  one primary diagnostic trait to look for would be in brain size: Lucy had the brain volume of a modern chimp whereas habilis averaged about 50 percent more.

Any hominid fossil find as old and as complete as this one appears to be is tremendously exciting to physical anthropologists. Fossils are incredibly rare, only by a quirk of geology and chemistry do they exist at all. Whether or not this one fits nicely between Australopithecus afarensis and Homo habilis, remains to be seen. That news may be available in a few more days. There will be a full diagnosis here on the Austin Science Policy Examiner, if and when that happens.