Australopithecus saltationis

I found ID palaeontologist Günter Bechly’s article on the newly announced fossil hominid Australopithecus anamensis extremely thought provoking.

As usual the science itself is a lot more interesting than the press articles shoehorning it into the tired old “missing link” narrative with headlines about being “our direct ancestor” and text about it being the direct ancestor of Lucy (Australopithecus afarensis) who is also our direct ancestor.

Readers who have kept up with the field of human origins will know that there is a great ongoing debate about the relationship between the Australopithecines and the Homo line, and that evolutionary discussion nowadays never talks about direct ancestry, but only “sister groups.” Everybody has siblings, but the parents have all gone AWOL.

As Bechly’s piece points out, the interesting story is not about human emergence as such, but about the Australopithecine/Homo story being an example of an “evolutionary series” at the fine scale. It’s true that fossil remains of this series are scarce, but because of our personal interest in our beginnings, they are sought intensively and studied exhaustively.

We are looking, remember, at the changes between a few very closely-related forms over the last 4 million years. Or, to put it genetically, we are looking to explain the final 2% of changes since we are said to have diverged from the chimps. To use the genealogical analogy it’s about you and your grandad, not your descent from the Emperor Charlemagne.

Yet even at this small scale, the water is muddy. Grandad might actually be his half-brother. Bechly quotes the researcher Haile-Selassie (has anybody done his phylogeny with respect to the emperor of the same name?):

MRD has a mix of primitive and derived facial and cranial features that I didn’t expect to see on a single individual.

Bechly explains the anatomical detail that causes the problem here:

Because the new skull showed for the first time what the frontal bone of A. anamensis looked like, and how it differed from that of A. afarensis, scientists could finally determine the specific affinities of an isolated frontal bone (known as the “Belohdelie frontal”) that was discovered in 1981, also in the Afar region of Ethiopia (Asfaw 1987). It turned out to belong to A. afarensis, even though it is reliably dated to 3.9 million years, thus 100,000 years older than the new skull of A. anamensis. This implies that both species did overlap for a considerable period. Consequently, A. anamensis cannot have just transformed and dissolved into A. afarensis.

And so, he goes on to say, even at this near micro-scale of overlapping populations of similar creatures, the specialists are arguing about the relationships, because the evidence is mixed. That means that the fossils do not unequivocally show evidence for the gradualist transition of A. anamensis into A. afarensis, or vice versa.

This is a blow to the gradualist hypothesis because, as Bechly points out, this transition is one of only three “gradualist series” usually seen in textbooks, the other two being Steinheim freshwater snails, and Globorotalia foraminifers. This is pretty poor pickings from the rich fossil record of the entire world. But I think I may have mentioned in previous blogs the serious doubt that hangs over the latter two of these three, as Bechly goes on to recount.

Broadly, research has suggested that much of the variation in plankton is minor and intra-specific, and has also shown that cryptic diversity, rather than transition over time, explains much of what is found in the record. Furthermore Bechly cites a study that re-analysed the data on Globoratalia and concluded that it actually shows an example of “abrupt speciation.” Et tu, Brute.

As for the snails, it seems that most modern palaeontologists reject the series proposed way back in 1979, but that a rigorous cladistic analysis has still not been done to help settle the matter. Jury still out on the last exceptional case: hard cases make bad law.

And so the fossil record, as Gould and Etheridge (discussed by Bechly) pointed out decades ago, even more overwhelmingly than then shows stasis and saltation, rather than directional gradualism. Bechly, from within the palaeontology field, says that their punctuated equilibria theory has not fared as well as we might think amongst the majority, but Gould’s reminder that “stasis is data,” rather than an anomaly, is still to be taken seriously. There is fossil evidence for stasis and saltation – there is little fossil evidence for gradualism. That’s the lie of the land.

Meanwhile the essential completeness of the fossil record has been demonstrated in a number of ways. The Australopithicines are themselves one strand of the evidence – how many lost transitional species do we really think existed in the very same geographical area and time period between Australopithecus anamensis and Homo erectus? Or amongst the Australopithecines themselves, come to that?

This is not to deny that transitions occurred: biologically, it is most parsimonious to believe that one Australopithecine derived from another. What is at issue is the mechanism, understood in the broadest terms as a mechanism of cumulative gradual, directional changes. These are fundamental not only to classic Darwininian theory, but to any naturalistic theory currently extant.

For the crux is this, rightly pointed out by Richard Dawkins in 2009:

Evolution not only is a gradual process as a matter of fact; it has to be gradual if it is to do any explanatory work.

Whatever ones scientific theory of evolution, whether by natural selection, neutral change or even Lamarckian purposeiveness, it must be a process of gradual change. A saltation is not a process, but an event, which is necessarily as opaque to scientific explanation as any of Ovid’s sudden metamorphoses. Saltation into a novel form is, pretty much by definition, indistinguishable from creation by divine fiat. Indeed, it only becomes rationally coherent by assuming the divine.

But saltation is overwhelmingly the pattern of the fossil record, even when it comes to the finest level distinguishable. Punctuated equilibria theory simply accelerates gradualism beyond the resolution of fossils, and places it somewhere out of sight in small populations. “Maybe an assistant switched the wine jars” is not a scientific explanation of the miracle of Cana, but the application of a metaphysical assumption, ie that natural that is, gradual, explainable) changes must be happening even if there’s no evidence.

My minimal conclusion from all this is that the most complete Australopithecus skull so far discovered leaves us significantly less informed about how species transitions occur in nature than we were before. That doesn’t just mean a blow against “Darwinism” (in the ID shorthand), but against any genuinely explanatory theory, in Dawkins’s scientistic terms, of which I am aware.

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About Jon Garvey

Training in medicine (which was my career), social psychology and theology. Interests in most things, but especially the science-faith interface. The rest of my time, though, is spent writing, playing and recording music.
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