Science and Creationism 16 Anatomy Colin Frayn 2008

Science and Creationism 16. Anatomy © Colin Frayn, 2008 -2011 www. frayn. net

Homologous structures • Homologous structures are those that appear similar in related species • Evolution predicts that certain organs, over a great deal of time, may change their function as a lineage evolves • Exaptation : The modification of use of an existing organ for a different function in a direct evolutionary descendant. • Do similar features merely propose the same designer? – No, because in most cases the best option for a designer would have been to completely redesign the organ from scratch rather than modify an existing organ to do something that it wasn’t originally ‘meant’ to do – Also, we have intermediate stages for many of these © Colin Frayn, 2008 -2011 www. frayn. net

Haeckel’s Embryos (1) Stages of development A copy (1892) of Ernst Haeckel’s original embryo sketches Different animals © Colin Frayn, 2008 -2011 www. frayn. net

Haeckel’s Embryos (2) • Haeckel faked some aspects of his original drawings – They are nowadays accepted as fraud • Some aspects were accurate and relevant – ‘Recapitulation theory’ – Many aspects of ontogeny (embryo growth) really do echo historical evolutionary stages • Whales have hair and leg bones • A structure resembling the tail of primates recedes to form the human coccyx bone • Swim bladder of fish develops first as a component of the gut, according to its presumed evolution, and then later detaches from the gut completely © Colin Frayn, 2008 -2011 www. frayn. net

Ontogeny recapitulates phylogeny • The ‘subtitle’ of Haeckel’s Recapitulation hypothesis • This theory suggests that embryological stages remind us of the evolutionary history of an organism • This is somewhat true, but is largely discredited in the sense that Haeckel intended it © Colin Frayn, 2008 -2011 www. frayn. net

Gill slits in embryos • Do human embryos have ‘gill slits’ reminiscent of their evolutionary history? • No, though they do have features that resemble gill slits called pharyngeal pouches – In humans, these features have nothing to do with breathing – All vertebrate embryos have these – In fish, these do develop into gills – Common features are strong evidence for common ancestry © Colin Frayn, 2008 -2011 www. frayn. net

Vestigial organs are supposed ‘remnants’ of evolutionary history that have not yet fully disappeared • Tiny leg bones in whales • The human appendix • Eye remnants in blind cave fish These may have minor functions, but certainly not the ‘obvious’ ones. They are remnants of a more prominent organ which has become redundant. © Colin Frayn, 2008 -2011 www. frayn. net

The Eye Is the eye too complicated to have evolved? • The eye could easily have evolved in under a million years – Nilsson & Pelger (1994) • Many different eye types exist in nature – The eye has evolved many times • Maybe from a very simple common ancestor organ • Maybe totally independently • The eye is evidence of poor design – The retinal cells are ‘plugged in’ backwards! – The contrary claims of Michael Denton and others are not plausible © Colin Frayn, 2008 -2011 www. frayn. net

Eye Anatomy Blind spot where the optic nerve crosses the retina © Colin Frayn, 2008 -2011 www. frayn. net

Inverted Retinal Cells Photoreceptive cells in the retina are plugged in backwards • This means that: – Less light gets to the photo receptors – We have a blind spot – We are susceptible to many more blinding diseases • Is this is actually a good design after all? –No, these arguments fail • ID arguments are flawed – An intelligent designer would have designed the eye differently – The eye is forced to solve problems that need not even exist – Squid have retinas wired “correctly” and they see very well • …and no, their eyes don’t overheat! © Colin Frayn, 2008 -2011 www. frayn. net

Darwin and Eye Evolution • Did Darwin write “To suppose that the eye … could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree”? • Yes, and he followed it with the words: “Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real. ” • And then he quoted several pages of suggested evolutionary models. © Colin Frayn, 2008 -2011 www. frayn. net

Irreducible Complexity • Structures that cannot work if any one of their parts is not present – There are many of these, but… • Structures may have had alternate uses before evolving to their current form • Bacterial flagellum – An ‘engine’ for bacteria – A plausible evolutionary model exists – Lots of work has been done in this area • Immune system cascade – This poses no problem whatsoever – Models to explain the origin of chemical pathways are abundant © Colin Frayn, 2008 -2011 www. frayn. net

Behe at Dover • In the trial of Kitzmiller vs. Dover Area School District (2005), Michael Behe testified that several irreducibly complex systems exist. Quotes from Judge Jones’s ruling: “As expert testimony revealed, the qualification on what is meant by ‘irreducible complexity’ renders it meaningless as a criticism of evolution. In fact, theory of evolution proffers exaptation as a well-recognized, well-documented explanation for how systems with multiple parts could have evolved through natural means. ” “We therefore find that Professor Behe’s claim for irreducible complexity has been refuted in peer-reviewed research papers and has been rejected by the scientific community at large. ” “. . . on cross-examination, Professor Behe was questioned concerning his 1996 claim that science would never find an evolutionary explanation for the immune system. He was presented with fifty-eight peer-reviewed publications, nine books, and several immunology textbook chapters about the evolution of the immune system; however, he simply insisted that this was still not sufficient evidence of evolution, and that it was not ‘good enough. ’” © Colin Frayn, 2008 -2011 www. frayn. net