Friday, June 19, 2015

"Mr Darwin's 'Researches' abound in misstatements"

By total serendipity, I recently learned from an ornithologist friend of a fascinating letter in an 1870 issue of the Proceedings of the Zoological Society of London.  It's from a Mr W.H. Hudson, addressed to the secretary of the Society, concerning the ornithology of Buenos Aires, and it is one parry in a wonderful example of scientific disagreement in action.

WH Hudson; Wikipedia

Hudson was a prolific author, naturalist and ornithologist born in Argentina in 1841 to English parents.  He published a lot of his ornithological work in the Proceedings of the Zoological Society, and would have been well-known to readers.  In the letter I happened to stumble across, Hudson writes of four species of woodpecker found in and around Buenos Aires. After describing the first three species, Hudson goes on to the Carpintero, the bird that is really of interest to him, because he believes he can reveal Charles Darwin to be a sloppy scientist or worse, with serious implications for Darwin's theory.  I quote at length because rewording would do it injustice.
The fourth species is the 'Carpintero;' more widely distributed and better known than the other members of the genus to which it belongs, and also of great interest in reference to the erroneous account of its habits in Mr. Darwin’s work, which makes it worthy of particular attention. However close an observer a naturalist may be, it is not possible for him to know much of a species from seeing perhaps one or two individuals in the course of a rapid ride across the pampas. Certainly, if Mr. Darwin had truly known the habits of the bird, he would not have attempted to adduce from it an argument in favour of his theory of the origin of species. In Chap. VI. of his well-known work on this subject the author speaks of the altered habits, caused by change of habitat and other extraneous circumstances, and infers that it would be an easy matter for natural selection to step in and alter an animal’s structure so as to make a new species of it, after its habits have been so altered. He then proceeds to ask whether 'there can be a more striking instance of adaptation given than that of a Woodpecker for climbing trees and for seizing the insects in the chinks of the bark;' and, in reference to this, states that there is a Woodpecker inhabiting the plains of La Plata, ‘where not a tree grows,’ and which is consequently a Woodpecker which never climbs a tree’ (Origin of Species, 4th ed. ch. vi. pp. 2 12, 2 13).
Mr. Hudson continues,
The perusal of the passage quoted by one acquainted with the bird referred to and its habits might induce him to believe that the author had purposely wrested the truth in order to prove his theory; but as Mr. Darwin’s ‘Researches’ were written long before the theory of natural selection was conceived, and abound in similar misstatements when treating of this country, the error must be attributed to other causes. The facts are, that besides orchards, and groves of willow, poplar, etc, which have been planted wherever the plains are settled, there is also the continuous wood, which I have already described, growing on the shores of the La Plata.
Hudson goes on to describe in even more detail the woody habitat in which this woodpecker lives.  And then the coup de grace.
It is not only the erroneous account of this bird’s habits that makes Mr. Darwin’s mention of it peculiarly unfortunate, but also because this bird rather affords an argument against the truth of Mr. Darwin’s hypothesis. Mr. Darwin describes it as a perfect Woodpecker, not only in conformation, but in its colouring, undulatory flight, and shrill obstreperous cries.  It is plain then that natural selection has left it unaltered...
My my.  So, Darwin was wrong in his observations of the Buenos Aires region of Argentina, wrong about this woodpecker, and wrong about the role of natural selection in this bird's evolution.  If Hudson was right, one would have to conclude that Darwin was so driven to prove his theory of evolution by natural selection correct that he filtered all his observations though this light, altering them when they didn't fit his theory. Or, that because his ideas about evolution and natural selection were only beginning to percolate as he roamed the pampas of Argentina, and he hadn't recorded his observations with natural selection in mind, he had to rework them in light of his theory, thus forcing them to fit.  Either of these are perfectly plausible.

Magellenic woodpecker from Southern Argentina and Chile; probably not the species Darwin and Hudson disagreed about, but a South American woodpecker, on the ground, so it will have to do (Hudson doesn't note the species in his letter); Source: "Magellanic Woodpecker Male (Campephilus magellanicus)" by Butterfly austral - Serge Ouachée - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons

But there's another interpretation.  Here's the entire paragraph about that woodpecker from which Hudson chose just a few quotes:
Can a more striking instance of adaptation be given than that of a woodpecker for climbing trees and seizing insects in the chinks of the bark?  Yet in North America there are woodpeckers which feed largely on fruit, and other with elongated wings which chase insects on the wing.  On the plains of La Plata, where hardly a tree grows, there is a woodpecker (Colaptes campestris) which has two toes before and two behind, a long-pointed tongue, pointed tail-feathers, sufficiently stiff to support the bird in a vertical position on a post, but not so stiff as in the typical wood-peckers, and a straight strong beak.  The beak, however, is not so straight or so strong as in the typical woodpeckers but it is strong enough to bore into wood.  Hence this Colaptes, in all the essential parts of its structure, is a woodpecker.  Even in such trifling characters as the coloring, the harsh tone of the voice, and undulatory flight, its close blood-relationship to our common woodpecker is plainly declared; yet, as I can assert, not only from my own observations, but from those of the accurate Azara, in certain large districts it does not climb trees, and it makes its nest in holes in banks!  In certain other districts, however, this same woodpecker, as Mr. Hudson states, frequents trees, and bores holes in the trunk for its nest. (Origin of Species
This is a bird that mostly looks like a woodpecker, sounds like a woodpecker, but that lives in a variety of habitats, and has a variety of diets, as observed not only by Darwin as naturalist on the Beagle, but also by others.  And, Darwin has evidence of other woodpeckers that don't behave as woodpeckers ought -- they eat fruit and live in river banks!  This is exactly the kind of evidence that he sought to support his theory about adaptation.  What's going on?

Could it be that Mr. Hudson simply doesn't like Mr. Darwin's theory of evolution.  And that's what caused him to pick and choose his own evidence?  He was in fact well-known to Darwin as a good ornithologist, but Darwin also knew that Hudson didn't agree with him.  He stated plainly in his book that "Mr. Hudson is a strong disbeliever in evolution..." (Origin) And, Hudson is known to historians, as well.  He was a strong religious believer and very unhappy with Darwin's theory because it challenged his belief.  He was also unhappy with Darwin himself, because his own faith had been challenged.  According to Novoa and Divine, he was happier with Lamarck's explanations of evolution because they allowed for religious belief.

So, in the end, it seems this is not an honest disagreement between two scientists evaluating the evidence with nothing but curiosity about which interpretation is correct.  This is one scientist unhappy with another's ideas, even willing to go to the brink of accusing him of lying, something Darwin had no respect for, as he wrote in the Zoological Society Proceedings in 1870: "I should be loathe to think that there are many naturalists who, without any evidence, would accuse a fellow worker of telling a deliberate falsehood to prove his theory."  He did slightly expand on his description of the woodpecker in the 6th edition of Origin, saying that "in certain large districts it does not climb trees".  So, he took Hudson's critique to heart enough to clarify his observations, but it is clear that Hudson's critique was wrong, and driven by motives other than science.  

Still, there's a lesson here, and that is that science being a human pursuit, the same motives, blindnesses, conceits, passions and adherence to belief can drive what is in theory supposed to be objective evaluation of observations as they drive politics or religion.  Darwin was surely affected by his own interpretive frame when viewing nature, as we all are.  Even had he made a blinkered mistake, that in itself would not count against his theory. But he was very honorable and an extremely careful observer, and it would have been surprising if Hudson had been right.  But not unthinkable, Darwin being human too.


Africa Gómez said...

Hudson doesn't directly, but Darwin mentions the species, Colaptes campestris, and Wikipedia supports Darwin on the ground living habits of this woodpecker,

Anne Buchanan said...

Indeed, thank you!

Holly Dunsworth said...

What a fun find, Anne!
Darwin's defensiveness played out in the footnotes of the newer and newer editions is entertaining in a bit of a macabre way I suppose. My favorite bit is in Descent when he was accused of fibbing about a clever baboon that chewed off the annoying sharp claws of a kitten. This was too tall a tale for his detractor so Darwin did the only thing he could. He found a kitten and chewed off its claws to prove that primate incisors could easily do the trick.

Anne Buchanan said...

That's a great story! Darwin was so worried about someone finding some fact that would prove his theory wrong. He must have gotten tired of having to deal with doubters of the trivial stuff, though, like this.

Holly Dunsworth said...

He relied so heavily on second-hand knowledge too. But don't we all?