In 2001 Stephen Meyer, Paul Nelson and Paul Chien wrote a lengthy discourse that explored the scientific challenges that the Cambrian Explosion of life poses to the Darwinian account of animal origins (1). Central to their arguments was the idea that biological processes in the organismic context are so tightly integrated that changes in one process invariably require compensatory changes elsewhere (1). Their illustration of this basic premise seemed intuitive enough:
“If an engineer modifies the length of the piston rods in an internal combustion engine, but does not modify the crankshaft accordingly, the engine won’t start. Similarly, processes of development are so tightly integrated temporally and spatially that one change early in development will require a host of other coordinated changes in separate but functionally interrelated developmental processes downstream” (1)
Drawing from examples cited in the biological literature and comments made by opinion leaders, notably geneticist John McDonald and zoologist Soren Løvtrup, the verdict they arrived at was that ”those genes which govern major changes, the very stuff of macroevolution, apparently do not vary, or vary only to the detriment of the organism” (1). In an effort to model the tight integration of biological processes my sons and I teamed up to assemble a functional multi-component machine better known as the K’Nex Drop-N-Swing. Not only did we successfully demonstrate how the operability of the ‘Drop-N-Swing’ mechanism was dependent upon the components having precisely the spatial dimensions that they display but we also showed how adjustments to any one of these required concordant adjustments elsewhere in the machine.
The layout of the Drop-N-Swing resembles the sky drop and swing carousel rides one finds in modern amusement parks (see http://www.youtube.com/watch?v=udr-RxcnUFU). On one side a centrally-located motor drives a series of four sequential gears each of which has just enough gear teeth to crank a chain-linked chair lift up a two foot-tall tower. Because a defined portion of the circumference of the largest gear lacks teeth and can therefore not crank up any weight, the chair drops down immediately upon reaching the top of the tower. This ‘rise and fall’ cycle is made possible through 86 chain links that form a closed chain circuit around two sprockets located at the bottom and top of the tower. The bottom sprocket is connected to the gear system that consequently turns the chain and causes it to lift up the chair.
As my sons toyed around with the Drop-N-Swing they found that they were unable to decrease the chain length and tower height without cutting down on the number of gear teeth. That is, if they were to maintain the rise and fall capabilities of the chair lift, concordant adjustments were needed at more than one location (otherwise the chair would get irreversibly stuck on the top sprocket). Even the tower height could not be facilely altered since the repeating unit of the tower struts did not correspond to an integral number of chain links.
Newsworthy cases in biology testify to the underlying charge brought by Meyer et al that major evo-morphing of structure and anatomy could not have been brought about through random piecemeal changes to already-extant body plans. Famously Nobel Prize winning biologist Ed Lewis elucidated crucial details about the genetics of embryonic patterning in fruit flies (2-4). Focusing on a group of genes known collectively amongst drosophila geneticists as the Bithorax Complex, Lewis built on the pioneering work of his predecessors who had identified homeotic (developmental patterning) mutants in the Bithorax gene that produced insects with an extra pair of wings (2-4). These appeared appended to the front portion of sophisticated flight balance-mediating organs called halteres situated on either side of the flies (2-4). The Bithorax mutant broke thorassic segment identities (ie one segment was replaced by another). But most importantly the mutant larva died early in development (2).
Meyer et al note how this additional wing pair “innovation” was viably unsustainable for the largely self evident reason that “the developmental mutation was not accompanied by the many other coordinated developmental changes that would have been necessary to ensure the production of the appropriate muscles at the appropriate place on the fly’s body” (1). Renowned Cambridge developmental biologist Peter Lawrence made his position clear in a review of the overall findings of homeotic mutation research:
“Homeotic mutations are encouraging because they raise the clarifying prospect of a class of controlling genes responsible for large chunks of the body pattern. They also impress because the mutations produce massive anatomical transformations; it was even thought such mutations could allow the sudden generation of new animal groups during evolution – an idea that looks increasingly implausible (individuals produced by such mutations are very unfit!).” (4)
One cannot help but acknowledge the futility of a story that claims that evolution could have brought about beneficial large scale changes to body plan architecture. The evidence speaks for itself. And simple attempts at modeling do nothing less than support the science.
- Stephen C. Meyer, Paul A. Nelson, and Paul Chien (2001) The Cambrian Explosion: Biology’s Big Bang, See http://www.discovery.org/articleFiles/PDFs/Cambrian.pdf, p.36, This article also appears in the peer-reviewed volume Darwinism, Design, and Public Education published with Michigan State University Press
- Vidyanand Nanjundiah (1996) The 1995 Nobel Prize in Physiology or Medicine, Resonance, http://www.ias.ac.in/resonance/Mar1996/pdf/Mar1996ResearchNews.pdf
- Stephen Jay Gould (2002) The Structure of Evolutionary Theory The Belknap Press of Harvard University Press Cambridge, Massachusetts, p.1096
- Peter Lawrence (1992), The Making of a Fly- The Genetics Of Animal Design, Blackwell Scientific Publications, London, p.211