Saturday, 18 January 2014

Why David Pearce's "Evidence for Design" fails to disprove evolution - 1

David Pearce’s “Evidence for Design”[1] is one of two Christadelphian-authored works of pseudoscience that the Christadelphian Magazine and Publishing Association sells.[2] Given that the fact of evolution has not been in doubt for well over a century[3] it reflects both Pearce’s ignorance of the subject that he criticises, as well as a failure of the CMPA to maintain the quality of material that it sells.

Pearce’s thesis is simply the argument from design dressed up in modern clothing. At heart, it is an argument from ignorance:
I cannot imagine how X evolved. Therefore it never evolved.
The flaw in this argument is painfully easy to see. Just because Pearce cannot imagine a plausible evolutionary pathway for the evolution of a structure does not mean that one does not exist. Anyone with even a nodding acquaintance with the professional literature will be aware that the cumulative effect of mutation and selection is capable of producing design. In fact, evolutionary algorithms, which exploit this Darwinian mechanism are more than capable of producing design without a designer.[4]

Another problem with the argument from design is that creationists such as Pearce are unwilling to accept the fact that suboptimal, flawed design is rife in the natural world. If Pearce is willing to exult in what he thinks is elegant design, then he is obliged to explain why God would create flawed, incompetent structures such as:

  • The male prostate, which stupidly encircles the urethra, resulting in an increased likelihood of urinary obstruction when it enlarges in old age
  • The vertebrate eye, which has the light-sensing cells pointing backwards away from the light. This results in an increased chance of retinal detachment and increases the likelihood of impaired vision from diabetic retinopathy. An eye with the light cells pointing towards the light (such as seen in the octopus) is immune from such problems.
  • The recurrent laryngeal nerve in humans and other mammals, which makes a pointless detour past the larynx, down the neck, under the aorta, then back to the larynx. It does not need to make this path – the nerves innervating the larynx could easily branch off and directly supply the larynx.
  • The human pancreas, which forms from two buds, rather than a single structure. Errors in embryogenesis can result in a ring pancreas which envelopes the duodenum, causing obstruction
  • Human sinuses drain poorly, and are prone to mucous clogging and infection.
  • Human testicles make a stupid descent from inside the abdomen, through the abdominal wall and outside. This creates a weakness in the abdominal wall, resulting in a higher risk of herniation, runs the risk of cryptorchidism (failure of testicle descent) which is a risk factor for testicular cancer and places a vulnerable structure outside.
  • Despite the fact we don’t need a yolk sac, we still make a vestigial version which can persist into post-uterine life as the Meckel’s diverticulum, a condition that can result in perforation and bleeding.[5]
Any creationist who wants to use ‘elegant design’ as proof of a designer needs to realise that the existence of flawed, incompetent, dangerous design could readily be used to prove that the designer is not perfect.

Finally, Pearce’s argument is predicated on a deeply flawed understanding of evolution. Evolution refers both to the fact of common descent and large-scale evolutionary chance, and the theoretical mechanism proposed to explain it. The latter is still a subject of active research, but the former is one of the best attested facts in history. Pearce has no excuse for failing to grasp this difference as Darwin on no less than two occasions made this difference explicit. In 1863 he stated that:
Whether the naturalist believes in the views given by Lamarck, or Geoffroy St.-Hilaire, by the author of the ‘Vestiges,’ by Mr. Wallace and myself, or in any other such view, signifies extremely little in comparison with the admission that species have descended from other species and have not been created immutable; for he who admits this as a great truth has a wide field opened to him for further inquiry.[6]
Creationists forget that in The Origin of Species, Darwin assembled evidence for evolution from comparative anatomy, biogeography and embryology, then proposed natural selection as his explanation for how evolution had occurred. He made this explicit in The Descent of Man:
 Some of those who admit the principle of evolution, but reject natural selection, seem to forget, when criticising my book, that I had the above two objects in view; hence if I have erred in giving to natural selection great power, which I am very far from admitting, or in having exaggerated its power, which is in itself probable, I have at least, as I hope, done good service in aiding to overthrow the dogma of separate creations.[7]
While the lack of a robust theory of inheritance meant that Darwin’s theory of natural selection never really gained traction, and in fact fell out of favour from the late 19th to the early 20th centuries, the fact of evolution very quickly was accepted by professional biologists as Darwin’s evidence for such change was regarded as compelling. Over the 150 years since then, the case for evolution has become overwhelming. As TR Gregory notes:
Over the past 150 years, [Darwin’s] initial list has been supplemented by countless observations in paleontology, comparative anatomy, developmental biology, molecular biology, and (most recently) comparative genomics, and through direct observations of evolutionary change in both natural and experimental populations. Each of thousands of peer-reviewed articles published every year in scientific journals provides further confirmation (though, as Futuyma…notes, “no biologist today would think of publishing a paper on ‘new evidence for evolution’ ... it simply hasn’t been an issue in scientific circles for more than a century”). Conversely, no reliable observation has ever been found to contradict the general notion of common descent. It should come as no surprise, then, that the scientific community at large has accepted evolutionary descent as a historical reality since Darwin’s time and considers it among the most reliably established and fundamentally important facts in all of science.[8]
Problems – real or imagined – in elucidating how an organ or structure may have evolved do not mean the evidence for common descent from multiple independent fields such as biogeography, palaeontology and comparative genomics go away. This is about as ludicrous as asserting that the failure of general relativity to explain quantum gravity means rocks do not fall when dropped, planets do not orbit their sun and gravitational lensing does not exist. Pearce’s failure to recognise these facts means his book is automatically discredited, as it fails to recognise what evolution really means and why mainstream scientists regard it as a fact. It attacks a straw man version of evolution.

There is however some benefit in picking over the book to expose Pearce's errors of fact and logic, if only to ensure that this book becomes little more than an embarrassing footnote in Christadelphian history.

[1] Pearce D “Evidence for Design” (2008: The Christadelphian Magazine & Publishing Association Ltd.)

[2] The other is “Creation or Evolution?” by John Hellawell.

[3] A little over ten years after Darwin first published The Origin of Species, W Bennett notes that “The fascinating hypothesis of [descent with modification] has, within the last few years, so completely taken hold of the scientific mind, both in [Great Britain] and in Germany, that almost the whole of our rising men of science may be classed as belonging to this school of thought. Probably since the time of Newton no man has had so great an influence over the development of scientific thought as Mr. Darwin.”  This consensus has remained solid ever since, and nothing has emerged to throw doubt on the fact of common descent and large-scale evolutionary change. See Bennett AW. The theory of natural selection from a mathematical point of view. Nature (1870) 3:30–33.

[4] Marczyk A “Genetic Algorithms and Evolutionary Computation” (2004: TalkOrigins Archive) Cited 18th January 2014

[5] Mant of these examples are documented in Held, Jr “Quirks of Human Anatomy: An Evo:Devo Look at the Human Body” (2009: Cambridge University Press)

[6] Darwin CR Origin of Species [Letter] Athenaeum. 9 May: 617, 1863

[7] Darwin C. The descent of man, and selection in relation to sex. London: John Murray; 1871.

[8] Gregory TR “Evolution as Fact, Theory and Path” Evo Edu Outreach (2008) 1:46-52