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“Transitional Vertebrate Fossils”

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Kathleen Hunt’s Talk.Origins FAQ on transitional vertebrate fossils has been available for years. The URL for that FAQ is http://www.talkorigins.org/faqs/faq-transitional.html. You might enjoy comparing it with Richard Milton’s response at http://www.alternativescience.com/talk-origins-transitions.htm.

re transitionals I was doing some research trying to track the loss of regenerative capability in most tetrapods. As most people know you can cut the butt off an earthworm and it'll grow a new one. Do that to a human and he's up crap creek without a paddle (so to speak). Amphibians have remarkable regenerative capability as well so it persisted into at least some tetrapods. Molecular homology (which admittedly is all over the map and doesn't jive with the fossil record, morphological taxonomy, or even with molecular homologies conducted on different proteins) places amphibians as ancestors to mammals. That ancestry seems about right from a number of angles (and you thought being descended from a monkey was bad - try Kermit the Frog). Regardless, we obviously we had regenerative capability in our past sometime as we all grew from a single cell that has the complete program in it for our adult form and every descendant cell (red blood cells excepted) has the entire program in it too. It seems to me that regeneration is a terrible thing to lose (fitness wise) and I was wondering what possible natural selection apology was made to explain the loss. I found two that sounded a little lame and of course, like every other Darwinian fairy tale, have no empirical evidence to back them up. Obviously we had regenerative capability in our past 1) someone opined that advanced immune systems shut down the regenerative response (which doesn't go very far in explaining why reptiles lost it) 2) someone else speculated that it was a tradeoff made for tumor suppression as they thought the same regulatory pathway that regenerates limbs can go haywire and generate tumors Anyone know of any other attempts to explain the loss? What got me thinking about it was reflecting on Genesis (I was trying to see if I'd overlooked any other credits). I've entertained the notion from time to time that (if) God created a perfect world with no death in it. Mankind then screwed the pooch with original sin and God cast him out. If that's anywhere near literally true it might mean that at one time there was a perfect genome and rather than evolving over time it has actually been devolving since God said (more or less) you're on your own now and life ain't gonna be a bowl of cherries. So anyhow that got me to thinking about devolution and that got me to thinking about things lost and that got me to thinking about regeneration and why on earth we might've lost that capability if natural selection is operating as advertised. DaveScot
re Transitionals JA Davision makes the same claim that the indisputable testimony of the fossil record is one of saltation - no gradual changes beyond the subspecies or varietal level. Instead he points to chromosomal rearrangments, which by definition must happen instantaneously in one individual, as the real mechanism of speciation. In sexually reproducing species this begs the question of how both male and females that can interbreed are produced since the chromosomal rearrangement bars interbreeding with the parent species. Instead of letting that question hang unanswered, in 1984 he developed and published (in a peer reviewed biology journal) the semi-meiotic hypothesis. Briefly it states that meiosis, a two stage process where the diploid genome of the parent separates into two hapliod strands and in the second stage recombines with a haploid strand from the other parent, can be interrupted so the second stage never happens and two haploid strands from the mother recombine into a homozygous individual. Moreover, he points to experimental evidence showing that these individuals with homozygous female chromosomes can develop into either male or female individuals. Thus a female whose gametes underwent chromsomal reorganization and such reorganization was faithfully replicated in a large number of eggs, can produce male and female offspring of a different species. He points out experiments conducted with frogs where her eggs were stimulated into growth by piercing with a needle instead of piercing by a sperm producing viable offspring - ie virgin birth. Skin grafts were conducted with these offspring and it was found that the mother would accept a skin graft from any progeny as all the DNA was hers and her immune system wouldn't reject them as "not mine". She wouldn't accept a graft from normal meiotic offspring as half the DNA wasn't hers and triggered an immune response. The more interesting thing is that skin grafts between the homozygous offspring weren't always successful indicating that while their DNA was wholly obtained from the mother it wasn't always the same between individual offspring. Further, Davison believes that ontogenesis and phylogenesis are both front-loaded self-terminating processes - pre-programmed sequences where chance and environment played little if any role in the process. Chance and environment play virtually no role in ontogenesis and he sees no evidence that chance and environment played any significant role in phylogenesis with the possible exception that environmental cues trigger saltation events. He believes that sexual reproduction and natural selection serve only to stabilize a species until its eventual extinction. He also has high confidence (if not firm conviction) that evolution (macro evolution) is finished and that rational man is the terminal product of phylogenesis. A stubborn determinist, he believes that phylogenetic evolution was writ in granite (so to speak) at the instant of the Big Bang and chance never played any role in the unfolding of the universe and the life it contains. I spent a long time studying his work and talking with him about it in private correspondence (hundreds of emails) and for the life of me I can't find any fault in it. It's wholly consistent and firmly grounded in empirical evidence. Of course the neo-Darwinists dismiss him as a noisy cantankerous old crank and while I sympathize with the noisy canterkerous old characterization (at least in informal settings) I can't find any justification in the crank part. He's as sharp as a tack, logical to a fault, and exceedingly well informed in biology after a career in it spanning almost 50 years. Sorry for such a long Davison rant. I just think his work deserves far more expert scrutiny than it has received. Anti-Darwinians just don't get any respect in the Darwinian-dominated atheist establishment. DaveScot
Bill, I want to thank you for sharing your mind gratis. I feel like I'm getting an education from a master sans tuition and cost of textbooks. Drexler in his 1986 book "Engines of Creation" predicted the explosive dissemination of information via hypertext and a world wide network. He also predicted that the explosion would be largely mediated by editors such as yourself who sort through the memes separating the wheat from the chaff. I read the book in 1987 and for the next 13 years made the development of low cost networked personal computers, essential infrastructure for the information explosion, the focus of my career. These days I just use PCs as I'm satisfied that the task of making them into an essential commodity was accomplished successfully (tip 'o the hat to another mentor of mine; Michael Dell). Content and discrimination thereof, not hardware, is what it's all about now. The job is now yours. Anyhow, thanks for all the wheat! EoC itself has been translated to hypertext and is available at no cost here. http://www.foresight.org/EOC/ It's worth reading for anyone that hasn't. Many of the predictions are now historical fact and the remaining predictions I believe will come to pass, hopefully in my lifetime. Just for grins I searched the pdf version for the word "meme". 68 occurrences. I guess that explains why I think memes are an important concept. I never read Dawkins' book where the term was first coined. DaveScot

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