Falconry and parrotry

I always seem to be picking on Springwatch, whose last programme of the season I watched from a recording yesterday. But the show exemplifies the “we now knowism” of popular science, in which all the uncertainties and frank contradictions are air-brushed away to produce a religious faith in Science™. In this case the subject was birds of prey.

There was a great selection of these in this series, from peregrines to goshawks, and ospreys to white-tailed eagles. So it was not surprising to have a “science item” on them. The story the venerable Chris Packham chose was how, in the bad old days when we were only able to judge by appearances, the hawks (broad wings) and the falcons (narrow wings) were believed to be closely related. But now that we have genomic studies (he said) they have been shown to have diverged 60 million years ago, in the Cretaceous period of T. rex etc.

He then proceeded with an “it’s not too surprising after all” section, in which the broad-winged goshawk, twisting through impossibly small gaps in the undergrowth to out-manoeuvre its prey, was contrasted with the peregrine stooping from the open sky at 200mph to knock out an unsuspecting pigeon. The distinction, though, is not always so clear, if you’ve ever had trouble distinguishing a kestrel (falcon) hovering on the lookout for prey with a buzzard (hawk) doing the same on a windy day.

The piece continued with the surprising genetic finding that the falcons are much more closely related to parrots than to hawks (and then Packham shows diagrams of how much a parakeet’s bill designed for fruit resembles that of a peregrine designed for flesh – the two really are more alike than you’d expect).

Finally, he explained the close resemblances between the actually only distantly related falcons and hawks as evolutionary convergence, and so nature was neatly explained for us all.

There are many things to question in this. The first is that pre-genetic morphological classification was never simply based on appearance, but on the supposed homologies that form the whole foundation of evolutionary theory. Thus my 1935 Cambridge Zoology text, although distinguishing the sub-order Cathartae (falcons) from the Accipitres (hawks), seals their relatedness thus:

All agree in the strong “raptorial” bill with basal cere, the U-shaped furcula, the large crop, the carnivorous habits, the great powers of flight, the superior size of the female, and the long nest-occupation of the young; but the Cathartae differ in having previous nostrils, no syringeal muscles, less flattened metatarsal, and so forth.

Then Packham has glossed over the major problem in evolutionary science of tree-disparity between palaeontological evidence, and genomic and molecular-clock evidence, and also of disparity between molecular phylogenies themselves, depending on the criteria chosen.

One common instance of this is that molecular-clock calculations regularly show the origin of groups to be millions of years earlier than the fossil record indicates, and that is so in this case: Packham’s source places the split in the Cretaceous, but no fossil representative of either group is found before the Eocene. In fact, only the chicken and duck clades of modern birds have ever been found in the Cretaceous. Wikipedia is more honest about the uncertainty. Speaking of the Accipitridae it says,

Accipitrids are known since Early Eocene times, or about from 50 mya onwards, but these early remains are too fragmentary and/or basal to properly assign a place in the phylogeny. Likewise, molecular methods are of limited value in determining evolutionary relationships of and within the accipitrids.

The same uncertainty is also hinted at in an article about the falcons, which alludes to the re-assignment of the group to the household of parrots rather than hawks as it says:

…most current molecular analyses recover them in a clade together with seriemas (Cariamiformes), parrots (Psittaciformes), and passerines (Passeriformes) [citations omitted, my emphasis].

This indicates that some molecular analyses tell a different story, and that is why some authorities disagree with the new classification. Slam dunk it is not – but the question is why the story is unclear. Shouldn’t different methodologies result in more or less the same tree?Even at higher resolution, molecules seem to tell variable stories. To quote, once again, the Wikipedia article on Accipitridae:

The accipitrids have been variously divided into some five to ten subfamilies. Most share a very similar morphology, but many of these groups contain taxa that are more aberrant. These are placed in their respective position more for lack of better evidence than anything else. The phylogenetic layout of the accipitrids has thus always been a matter of dispute.
The accipitrids are recognizable by a peculiar rearrangement of their chromosomes. Apart from this, morphology and mtDNA cytochrome b sequence data give a confusing picture of these birds’ inter-relationships.

We can’t sort out the recent history, then, but we tell the origin story confidently. To me, that sounds a little like not being able to forecast tomorrow’s weather correctly, but being certain about the climate in 2050. So the close morphological affinities between hawks and falcons are, it seems, illusory, whereas the real relatives of falcons are the parrots and passerines, of which my already-quoted falcon article says:

These taxa exhibit very disparate morphologies and none is particularly close to falcons in anatomy, behavior, or ecology.

We should, therefore, be more than a little suspicious of Chris Packham’s comparisons of peregrine and parrot beaks, for it means nothing in evolutionary terms. We could play the same game by comparing the beak of the parrot with that of a goshawk to claim kinship. The resemblance in either case is no more to do with homology than is the duck-bill of the platypus a sign of relationship to mallards.

The goshawk’s bill is similar to that of the peregrine, we are told, only through tens of millions of years of convergent evolution. Though since both groups have typical representatives in the Eocene, the convergence actually seems to have been far more sudden, if not saltational.

Packham puts convergence down, in almost teleological terms, to the requirements of being a raptor (begging the question of how and why you become a raptor before the necessary adaptations occur). Evolutionary biologists are prone to attributing convergence to a whole raft of other, hypothetical, accidents, such as horizontal gene transfer (how much of that has been shown to in higher animals, and how would it happen?) “ghost lineages” or “incomplete lineage sorting.”

And therein lies the rub of the whole issue. You discover that the homologies that led biologists to propose evolutionary theory bear little resemblance to what you now believe may have taken place in evolution, so that peregrines are first cousins of sparrows and only sixth cousins several times removed of the eagles and hawks they resemble most to the morphologist, the bird-watcher and the falconer. Then of what value is evolutionary theory? It explains nothing, it predicts nothing and it cannot even produce agreement between its various methodologies. Which is more interesting – that you and I may share a common ancestor who was a pikeman in Latvia a thousand years ago, or that we both like C. S. Lewis or study archaeology?

Evolution thereby becomes merely a belief system that enables the atheist to claim some intellectual respectability, as Dawkins famously said. Maybe undermining religion is its only real function. And yet, what intellectual credibility can come from a theory that tells us that the very patterns in nature that led to the theory are really just coincidences? Evolution can produce parrots and peregrines from the same parents, or alternatively it can transmute strangers into brothers. In neither case have we any decent explanation for how, why or even when. In what way is that more explanatory than special creation?