In another thread a creationist posted material from a creationist website that made my jaw hit the floor. It read . . .
quote:Actually, the molecular clock has many problems for the evolutionist. Not only are there the anomalies and common Designer arguments I mentioned above, but they actually support a creation of distinct types within ordered groups, not continuous evolution, as non-creationist microbiologist Dr Michael Denton pointed out in Evolution: A Theory in Crisis. For example, when comparing the amino acid sequence of cytochrome C of a bacterium (a prokaryote) with such widely diverse eukaryotes as yeast, wheat, silkmoth, pigeon, and horse, all of these have practically the same percentage difference with the bacterium (64¨C69%). There is no intermediate cytochrome between prokaryotes and eukaryotes, and no hint that the ¡®higher¡¯ organism such as a horse has diverged more than the ¡®lower¡¯ organism such as the yeast.
The same sort of pattern is observed when comparing cytochrome C of the invertebrate silkmoth with the vertebrates lamprey, carp, turtle, pigeon, and horse. All the vertebrates are equally divergent from the silkmoth (27¨C30%). Yet again, comparing globins of a lamprey (a ¡®primitive¡¯ cyclostome or jawless fish) with a carp, frog, chicken, kangaroo, and human, they are all about equidistant (73¨C81%). Cytochrome C¡¯s compared between a carp and a bullfrog, turtle, chicken, rabbit, and horse yield a constant difference of 13¨C14%. There is no trace of any transitional series of cyclostome ¡ú fish ¡ú amphibian ¡ú reptile ¡ú mammal or bird. http://creation.com/...mmon-design-points-to-common-ancestry
I expect less knowledgeable creationists to make this rather obvious mistake, but here is Creation Ministries International just embarrassing themselves.
For those who don't understand just how mistaken CMI is, here is a simple picture to clear things up:
All modern species are equally evolved. All modern species are at the tips of the branches, not at the fork in the branches. A fish shouldn't have DNA more like that of a bacteria. A fungus should not have DNA more like that of a bacteria. Why?
The answer is simple. Just ask what the common ancestor of two species should be, and then see if it is the same common ancestor.
What is the common ancestor of bacteria and humans? What is the common ancestor of bacteria and fish? What is the common ancestor of bacteria and yeast? What is the common ancestor of bacteria and wheat?
The answer to every one of those questions is the same. The common ancestor in every case is the same exact common ancestor, the common ancestor of all eukaryotes. Therefore, all eukaryote species should be equidistant from bacteria, AND THEY ARE!!!!!
CMI points to one of the most striking pieces of evidence FOR evolution, and mishandles it in such a striking and dumfounding way, especially for an organization that is supposed to be at the "cutting edge" of science based creationism. Go figure.
I just found the email from 1997 where I described what Denton wrote. It turns out that Denton had himself discovered the correct interpretation only to spend the rest of the chapter trying to explain it away. BTW, I got the diagrams from the NCSE's Creation/Evolution Newsletter, which I verified from Denton's book:
quote:However, you did make the same mistake as Michael Denton did in misinterpreting the findings. Since proteins continue to change over generational time, we cannot realistically expect comparison of modern proteins to yield the progression of changes from species to species; modern terrestrial vertebrates did NOT descend from modern lampreys, but rather they and modern lampreys descended from a common ancestor. Rather, what we would expect from evolutionary theory would be that the more time that has passed since the two species shared a common ancestor, the greater the differences would be between their proteins and when comparing a member of one such group of species against the members of the second group, we should expect the latter to all have the same degree of difference from the former (unless natural selection had come into play, of course; "molecular clocks" rely on the accumulation of neutral mutations -- see my bullfrog.html file for more on this). Therefore, we would expect to find that humans and apes would be more similar to each other since they shared a more recent common ancestor. We would also expect all felines to be more similar to each other for the same reason. And we would expect the lamprey to be about equally different from terrestrial vertebrates since the terrestrial vertebrates share the same common ancestor with the lamprey just before it split off from that line.
And what does the evidence show? Precisely what we would expect and precisely what would make sense. Your findings are indeed supportive of what evolutionary theory would lead us to expect.
Indeed, when Denton went through this exercise himself, he sought to discredit the standard phylogenetic trees of evolutionary descent by using these degrees of difference to construct Venn diagrams and assigning the various species considered into their place in that diagram according to their degrees of difference. However, it turns out that his Venn diagrams quite naturally produce the very same standard phylogenetic trees of evolutionary descent that Denton had tried to discredit.
Let me explain (something that would be impossible on the phone, since it involves graphical aids).
It seems that Denton made the typical creationist mistake of using "Ladder of Life" thinking (which, BTW, is Lamarckian, not Darwinian) -- i.e. assuming that all modern "primitive" organisms are identical to the earliest copies and that neither they nor their proteins have evolved since that group first appeared in the fossil record. Then he proceeds to compare the proteins of various groups of species looking for a linear progression and complaining when he does not find it.
For example, on page 284 of his book, Denton compares hemoglobin sequences of the lamprey and five other species (carp, frog, chicken, kangaroo, and human) and fails to find the linear progression of [cyclostome --> fish --> amphibian --> reptile --> mammal] that HE expects. The same thing happens when he makes the comparison based on cytochrome c.
But based on the cytochrome c data, he also constructs a Venn diagram which divides the species into classes and subclasses -- a set of nested areas which are not supposed to be a phylogenetic tree. I have copied that diagram here from page 286 (rendered in text graphics -- if your e-mail viewer uses a proportional font, then it will probably garbles this up; change the font to a monospace font, like Courier New):
Very interesting. Both trees fit the evolutionary view to a "T".
Of course, the linear view, the "Ladder of Life," is both wrong and unwarranted. Why should we expect ALL change to stop for the "more primitive" forms? The more correct way to view the data, the way in which biologists actually view it, is as I have told you already and as Denton finally describes it on page 294:
"The only way to explain this [pattern of protein differences] in evolutionary terms is to propose that since all the different lines of a group diverged each particular protein, such as haemoglobin or cytochrome C, has continued to evolve in each of the lines at its own characteristic uniform rate."
Scientists have known that all along. Even Darwin said the same thing, that the longer it has been since two organisms shared a common ancestor, the greater would be the differences between them. Furthermore, this is what we find in "green" fossils, fossil leafs which have not petrified and which still contain their proteins and DNA: while the form (morphology) of the fossil leaves was virtually indistinguishable from modern leaves, their biochemistry was very different and those differences are very orderly and allow scientists to construct phylogenetic trees.
Also on page 294, Denton plots a phylogenetic tree based on cytochrome sequence differences and for which the numbers fit very well. But now that Denton has finally stumbled onto a correct explanation, he spends the rest of the chapter trying to explain it away. For example, he discounts the possibility that the proteins could have continued to change because he cannot think of a mechanism that would direct those changes, even though he does mention, and discount out of hand, the "molecular clock" idea of the accumulation of neutral mutations. My problem is the opposite of Denton's; I cannot think of a mechanism outside of natural selection that would freeze a protein's sequence, which would not happen in the case of neutral mutations (ie, by definition a neutral mutation would not change the expression of that gene, thus giving natural selection nothing with which to distinguish the mutated gene from the unmutated gene).
At the time, it was reported that Denton learned a lot from the responses to his book, mainly that he actually knew a lot less than he had thought he did. He is supposed to have said that if he were to write it again, the book would be a lot different. However, he had no intention to revisit the subject. From 2000 I stated that he had reportedly changed his position to theistic evolution, but I do not remember the details nor what my source was.
Still, it can be fun to watch an opponent to an interpretation arrive at that interpretation entirely on his own and then try to explain it away. Though it does demonstrate how well the branching tree interpretation fits the data so well.
Just to clear up any confusion in the opening post, I am not saying that the common ancestor of modern bacteria and eukaryotes is necessarily a eukaryote. What I am saying is that if you start with any modern bacteria and any modern eukaryote and trace their lineages to where they meet, they will always meet at the same common ancestor. If I start with an E. coli and a human they will meet a specific node in the tree of life. If I start with a Streptococcal bacterial species and an elm, those lineages will meet at the very same node as humans and E. coli met at.