LIVEFREEORDIE Recent advances in biotechnology have brought some interesting new facts to light. It has long been known, for example, that humans and other primates lack the ability to synthesize vitamin C. That is why we get scurvy if we don't get enough of it in our diet. Other mammals (except guinea pigs), however, do have the ability to synthesize vitamin C. Scientists have studied those other mammals and understand quite a bit about the process of vitamin C synthesis and have actually identified the genes that control it. Now here is where things get interesting. Scientists took the gene sequences identified by the vitamin C research and searched for them on human and primate genomes. Suprisingly, they found the genetic sequences for vitamin C synthesis on each one, but in an inactive region (the technical term for such a region is a pseudogene). The genetic code to synthesize vitamin C is present on all primate genomes, but is inactivated due to a mutation. But that's not the end of it. Later research was done to identify the specific mutation that inactivated the vitamin C gene. Across all of the primate species studied (humans included), the mutation was identical. So the interesting facts are: 1. Primates cannot synthesize vitamin C, yet primate DNA contains all the genetic instructions to do so. 2. The specific mutation that disables vitamin C synthesis is identical across all primates. Again, evolution explains this quite nicely. Evolution says that all primates have a common ancestor, a proto-primate if you will. It is quite plausible that the proto-primate's diet was rich in natural sources of vitamin C. Thus, a mutation to the vitamin C synthesis machinery would have had no detrimental effect. Without any selective pressure, natural genetic drift over time would tend to increase the frequency of vitamin C-challenged individuals. Whether by chance or due to some unknown benefit, this eventually became the dominant mode and has been inherited by all of the proto-primate's ancestors ever since. Aside from that, however, I'd like to know how creationism explains these facts. Is it just some marvelous coincidence? Why would a creator give primates the genetic instructions to synthesize vitamin C if they were just going to be left non-functional? Why choose the exact same mutation to disable the gene across all primate species when there are probably thousands of possible ways of doing so? Why did the guinea pig get a different mutation? Why did the creator choose to make life harder for innocent monkeys, chimps, and apes? NEMESIS That's just kinda mean I think!!! But, that's an interesting fact nonetheless. I think that's a very good illustration of the randomness of nature and argument that the creator did not create life ... that it was a product of evolution. Maybe humans actually evolved to be able to process Vitamin C. DAVID PLAISTED Some thoughts: Mutations are not random. If there is a lot of vit. C available then it is an advantage to disable this gene so it would tend to spread. Since humans and apes are so similar their favored mutations (hotspots) may be similar as well. It's also hardly true that the pseudogenes are the same -- typical genes differ by one or two percent at least between humans and apes. It would be a surprise if this gene did not differ too. In addition, biologists are looking for common genes between humans and apes. If they spent as much time looking for common genes between humans and chickens, just think what they might find! In general, it needs to be determined whether common pseudogenes parallel accepted evolutionary classifications. Here are some other links dealing with this question: http://www.mhrc.net/pseudogene.htm http://www.grisda.org/origins/21091u.htm http://www.trueorigin.org/pseudogenes01.htm http://aig.smartbusiness.org/home/pdf_notice.asp?pdf=/Home/Area/Magazines/tj/docs/tj14_3-jw_pseudo.pdf ZERATUL Ah, dueling links. Can I play? David has been rebutted directly regarding his unusual ideas on pseudogenes. The link is http://www.talkorigins.org/faqs/molgen/plaisted.html Correct me if I am wrong, David, but I don't believe you have ever responded to this. HELEN Please consider the following on this thread: 1. If a population is getting enough vitamin C from its diet, then any mutation(s) knocking out the ability to code for vitamin C synthesis would not be selected against, and this 'knock out' mutation could spread throughout a population with no deleterious effects. This need not have anything to do with common descent, but rather with available food (and preferred food) for a population over a relatively long period of time. 2. If you look at the essay here: http://www.grisda.org/origins/12096.htm, you will find Table 2 -- very interesting. The conclusion to this short essay reads, "In conclusion, what has the study of many more taxa done? 1) It has greatly enriched our picture: rather than the long-held view that vitamin C is required in the diet of guinea pig, monkeys and man, we now see that it is required also by bats, at least some fish, and many birds; and on the other hand, not by all primates. Further, animals which make their own do so in different organs: the kidney, especially reptiles and birds; or the liver, especially mammals and perching birds. 2) There is evidence for a taxonomic explanation of part of the diversity between classes and between orders, but hardly data at lower taxonomic levels even to carry out a common statistical test. 3) It appears to provide more support for change by loss than by gain of capability. 3. And, in my email file from a geneticist in Europe: >"The identical position of the 1 bp deletion is not necessarily an >indication for the common ancestry. It is possible that a similar mechanism >has produced the frameshifts exactly in the same positions in the GLO genes >of different primates. The high sequence identity between the GLO genes in >primates could mean that there is at this specific site a sequence-based >tendency for a frameshift (i.e. an increased rate for the frameshift(s)). >The same mechanism can explain also other shared mutations in primates." I would suggest then, especially in view of the fact that we know only somewhere around 5-10% of gene sequences from the primates, that the vitamin C argument is mainly wishful thinking. It simply does not hold up well in light of closer examination. A lot more work needs to be done before this argument for common descent can be used in all honesty. DAVID PLAISTED I didn't realize this was a frameshift mutation. Anyway, it could be that the probability of this particular mutation is high compared to that of other mutations of this gene. Furthermore, if Vitamin C is abundant, then it would be an advantage to knock out this gene since the organism would not waste energy synthesizing this protein. So it is not difficult to see how the same mutation could occur in humans and other primates and spread to the whole population in both cases. Originally posted by Zeratul: Correct me if I am wrong, David, but I don't believe you have ever responded to this. I didn't think it needed a rebuttal and that my original post stood as it was. If you think I err, please inform.