Press Welcomes "Lucy Neighbor"
Another species of Australopithecus has been named. But does the evidence justify the big to-do in the media?
First, the facts. The discovery was announced in Nature by Yohannes Haile-Sellasie’s team (cf. 6/22/10). The find, in the Afar province of Ethiopia, consists of four fragments of jaws and teeth (no postcranial remains) from scattered locations meters apart, another over two km away in different geological strata. The fragments were found above and below a basalt layer, in layers of sand, silt, and tuff varying in depth by over 30 meters. The team linked these fragments with a partial foot (“Burtele foot”) over two km away that they announced in 2012. Magnetic readings throughout the layers show no magnetic reversals. Argon-argon dating of some sediments yielded radiometric ages between 3.3 to 3.5 million years for the sedimentary column containing the specimens.
So it’s not clear the fragments are associated with the same individual or group in space or time. Nevertheless, they gave this collection of bones a new species designation, Australopithecus deyiremeda [“southern ape, close relative”] calling it a “sister” to Australopithecus afarensis (“southern ape from Afar”, a.k.a. “Lucy”) and other “human ancestors.” But is it not a southern ape? Ancestry to Homo sapiens is an assumption, not a fact emerging from a few scattered teeth.
What does the evidence mean? Warning: some interpretation required:
The taxonomy and phylogenetic relationships among early hominins are becoming more complicated as new taxa are added to the Pliocene fossil record, and the temporal range and systematics of early Homo are reconsidered. A phylogenetic analysis of the preserved morphological features of Au. deyiremeda fails to produce a single most-parsimonious cladogram. However, the results are fairly consistent in placing this species as a sister taxon to a clade including Au. africanus, Paranthropus and Homo (Fig. 6 and Supplementary Notes 6,7,8). There are many alternative phylogenies consistent with this topology, but the fact that Au. deyiremeda is positioned outside the Paranthropus and Homo clade implies that some features associated with one or both of these taxa are homoplastic [i.e., convergent]. Therefore, the addition of Au. deyiremeda reinforces questions about dentognathic [tooth and jaw] homoplasy in later Pliocene and early Pleistocene hominins.
Haile-Selassie has been somewhat of a gadfly in paleoanthropology circles, claiming for years that ape diversity in Africa was greater than expected 3-4 million years ago, with several species of “hominins” living side-by-side (for definition of “hominin,” see 3/25/15). This smudges the neat, iconic image of human progress from the apes (see 5/15/15 parodies). In another Nature commentary, Fred Spoor wonders whether these bones, containing a mosaic of primitive and derived features, warrant a new species designation. “Finding such taxonomic diversity raises the question of how multiple species could have coexisted over a long period in a stable ecosystem,” he adds, “particularly when they live in close geographic proximity, as seems to be the case with A. deyiremeda and A. afarensis.”
Nevertheless, the news media all accepted the team’s nomenclature and cheerfully welcomed a new “sister” into the human ancestral family. Too bad it didn’t have a catchy name (try saying “deyiremeda” five times real fast). Reporters, though, have long been habituated to the protocol. Armed with prepared boilerplate and press photos in hand, they started the party songs with gusto:
- “Found: our 3m-year-old forebear who lived alongside ‘Lucy’ …. There are few things more exciting to a palaeontologist than the discovery of a new species” (John McNabb, U of Southampton, in The Conversation)
- “New species of early human was Lucy’s neighbour in Africa” (Penny Sarchet in New Scientist)
- New human ancestor species from Ethiopia lived alongside Lucy’s species…. A new relative joins “Lucy” on the human family tree (PhysOrg and Science Daily)
- New human ancestor was Lucy’s cousin and neighbor (Michael Balter in Science Magazine)
- ‘New species’ of ancient human found (Rebecca Morelle in the BBC News).
This press ritual is old and predictable. It’s apparently too tedious for the public to be told that the traits of these bones “fail to produce a single most-parsimonius cladogram,” or that “many alternative phylogenies” are “consistent with this topology,” that the bones were scattered over a wide area in multiple levels of sediments, that mosaics of traits are inconsistent with the picture of progress from ape to man, or that homoplasy (convergent evolution) is unexpected for separately-evolving groups.
Under the bold headlines, a few of the articles did point out problems with the claims. Michael Balter in Science took leave of the party early enough to notice, “some skeptics argue that the new fossils might be variant individuals of Lucy’s own species.” McNabb urged a measure of caution: “Exactly where A. deyiremeda fits in among our ancestors is, however, hard to know.” And in a Nature piece accompanying the paper, Ewen Callaway captured Fred Spoor’s dramatization:
The distinct jaw shapes of A. deyiremeda and A. afarensis could mean that they used their teeth on different kinds of food. But with so little evidence to hand, Spoor warns against jumping to conclusions about the relationship between the two species. “We shouldn’t suddenly think they stood at the Awash River, shook hands and said, ‘What are you doing here?’”
Veteran paleoanthropologists like Haile-Selassie know better than to expect calm acceptance of his new bones. Here he is quoted in Science Daily:
“This new species from Ethiopia takes the ongoing debate on early hominin diversity to another level,” said Haile-Selassie. “Some of our colleagues are going to be skeptical about this new species, which is not unusual. However, I think it is time that we look into the earlier phases of our evolution with an open mind and carefully examine the currently available fossil evidence rather than immediately dismissing the fossils that do not fit our long-held hypotheses,” said Haile-Selassie.
Hardly anyone could disagree with that. But by calling it “this new species,” has he shown open-mindedness about whether it is a species at all? Has he, by referring uncritically to “the earlier phases of our evolution,” shown open-mindedness about evolution? Does he dismiss fossils such as the Cambrian explosion and soft-tissue dinosaur evidence that might not fit his own long-held hypotheses? As Darwin himself advised, “A fair result can only be obtained by fully stating and balancing the facts and arguments on both sides of each question.” Unfortunately, he next stated in his Introduction to The Origin of Species that he didn’t have time to do that: “and this cannot possibly be here done.” After the party’s over, maybe.
Update 5/28/15: Casey Luskin evaluates the claim in Evolution News & Views, focusing on the trivial nature of the fragments leading to overblown interpretations.
Man, does this get tiresome. It’s like watching an irrational cultural ritual play itself out every few months, each time the head honcho of the competing teams gets the spotlight. Haile-Selassie knows that he’s only going to get fame if he can call it a new species, so to the Rift with the facts; let’s give these puzzling fragments a new name! How about “close relative”— What? Not jargony enough? Hurry, translate it into an Ethiopian dialect so we can Latinize it for Nature. One thing he forgot was to personalize his bones (e.g., Lucy, Ardi, Ida, Handyman) for the low-information reporters.
Dead apes tell no tales. Their handlers do. The ape(s) that left behind a few teeth back there aren’t able to jawbone about what a bunch of hype this is. Nor can they demonstrate the intelligent design of those molars and jaws that allow us mammals to traverse God’s green earth and gain sustenance from the rich habitat provided for us. That will be the job of our better-informed readers of Creation-Evolution Headlines.