Long ago a wise king solved an interfamily dispute with a simple solution: split the baby. Now paleoanthropologists are fighting–with little resolution in sight–about how to interpret newly discovered hominid fossils, which comprise about 130 bones from multiple individuals. Focused on a single juvenile specimen, the debate is over whether the fossils represent human evolutionary ancestors, just a new species that split off and went extinct, or another previously known species of little significance to human evolution. While many news articles are touting the fossil as a human ancestor or even a “missing link” (see, for example, AOL news or the London Telegraph), what’s encouraging is a couple sources in the mainstream media (though just a couple) are functioning like actual real journalism outlets and citing a variety of credible authorities who dissent from the standard line that this fossil is a link in human evolution.
Perhaps unsurprisingly, the paleoanthropologist who just happened to have discovered the fossils had this to say:
- “They make a very good candidate ancestor” (Lee Berger, quoted in the Wall Street Journal)
But even Dr. Berger offered a noteworthy retroactive confession of evolutionist ignorance about the paucity of fossils prior to this find:
- “Before this discovery, you could pretty much fit the entire record of fossils that are candidates for the origin of the genus Homo from this time period onto a small table.” (Lee Berger, in ScienceDaily)
Then come the real critics. Tim White, who last year released and promoted a competitor fossil, “Ardi,” with much fanfare, had this to say:
- “It doesn’t reveal the means by which our genus arose. It does not reveal the earliest members of our genus.” (Tim White, as quoted in the Wall Street Journal)
One voice of reason in paleoanthropology, Bernard Wood, urged caution about getting too excited over a couple traits which could often evolve independently, leading to homoplasy:
- Some of the creature’s most human traits may be misleading clues, … “This sort of face may have evolved more than once,” he said. “I think these fossils are evidence that the tree of human evolutionary history had lots of twigs, all but one of which became extinct.” (Paleoanthropologist Bernard Wood at George Washington University, quoted in the Wall Street Journal)
Some critics, such as this one, were quick to point out that this fossil is “surrounded by hype and over-interpretation”–a caution sign to scientists critically evaluating the data:
- “These remarkable facts would usually be enough to secure researchers a place in the history of science. Unfortunately, they seem not to have been enough in this instance, as the discovery is surrounded by hype and over-interpretation, in terms of its significance. To claim that these new fossils represent an ancestor of living humans is misleading and founded in error. Australopithecus sediba is the wrong species, in the wrong place, and at the wrong time. It is way too primitive to be the ancestor of the human genus Homo, one of our direct ancestors. For a start, fossil Homo is known from East Africa to be almost half-a-million years older. The skull, tooth and limb bone anatomy of the older Homo also looks very different from those of sediba. Finally, a number of key skulls compared to the new sediba remains have been incorrectly described, leading to false conclusions about its place in human evolution.” (Dr Darren Curnoe, specialist in human at the University of New South Wales, Australia, quoted in The Independent)
Speaking to Nature, critics implied the fossils’ discoverers are overhyping their claims to the media and have “not undertaken any competent analysis” of some very important data:
- White says that the suggestion by Berger and his team that this lineage split before the emergence of Homo is “fossil-free speculation”, adding that “the obsession with Homo in their title and text is difficult to understand outside of a media context”. (Tim White, quoted in a Nature news blurb)
- [T]he authors have “not undertaken any competent analysis of variation within A. africanus — something I do not understand in the context that three further skeletons have been found by the same team at Malapa”. (Anthropologist Fred Grine of Stony Brook University in New York quoted in a Nature news blurb)
- Both Grine and White are critical of the fact that most of the diagnosis of A. sediba is on the basis of a single immature individual, and point out that because anatomy changes during growth, the jury will be out until more complete adult remains are described. (Nature news blurb)
Even those who thought the fossil had transitional features had their doubts about its importance, and downplayed the importance of the small brain size:
- “They are a mixture of Australopithecus and human characters indicating a transitional form to Homo. Finding of such form is entirely expectable for this time period and the location in Southern Africa. I am not sure, however, whether a designation of a new separate species is necessary. In the human lineage there is a natural range of variation of characteristics of individuals and the new finds fit into this range. One of the features used by the authors as indicating a new species is the relatively small cranial capacity 420 ml. Hominid cranial capacity is highly variable, it does not correlate with intelligence and thus some individuals within the same species may have smaller, others larger, cranial capacity. No need to use it as a trait separating species.” (Professor Maciej Henneberg, the Wood Jones Professor of Anthropological and Comparative Anatomy at the University of Adelaide, quoted in The Independent)
And of course the Smithsonian Institution, known for claiming evolution is proved, no matter what evidence is found, tried to claim that all the disagreement is just more evidence for evolution:
- “Evolution is wonderfully messy,” said paleoanthropologist Richard Potts, director of the Smithsonian Institution’s Human Origins program, and such technical disputes are the norm.
I agree: “technical disputes” like these over questions like whether it’s a human ancestor, whether it’s a member of the genus Homo, and whether it’s even a new species are the norm. Which is precisely why overhyped claims of transitional status and human ancestry must be taken with great caution.
Update, 4/11/10: Carl Zimmer has an article at Slate Magazine with a good analysis of the situation after this find, quoting Harvard Professor of Human Evolutionary Biology Daniel Lieberman stating: “The origins of the genus Homo remain as murky as ever.”