cb@hlwpc.UUCP (Carl Blesch) (10/09/84)
>I read yesterday an article which discussed an idea put forth >by some scientist that birds and mammals are more closely related than >birds and reptiles. Anyway, one of the comments was that some research >about protein comparisons had indicated the closest relative to man >for the particular protein was a chicken. >However, I went back today and was unable to find the magazine again. >I was merely browsing among the periodical shelves and have no idea >where to find the magazine. I do remember that the reason I picked >it up was an article by Stephen Hawkings ( spelling? , The british >physicist confined to a wheelchair) about space and time and >singularities and the origin of the univerise. >Also, the magazine struck me as using "British" (as opposed to American) >english. >Rich Hammond The magazine was New Scientist -- I just read the Hawking interview myself a few days ago. Sorry I can't give you the date of the issue, because I just had a clip of the Hawking article -- not the whole magazine, and I've passed the clip along to someone else. I'd venture to say that it was sometime within the past two months, however. Carl Blesch
bill@utastro.UUCP (William H. Jefferys) (10/11/84)
> >I read yesterday an article which discussed an idea put forth > >by some scientist that birds and mammals are more closely related than > >birds and reptiles. Anyway, one of the comments was that some research > >about protein comparisons had indicated the closest relative to man > >for the particular protein was a chicken. > > >Rich Hammond > > The magazine was New Scientist -- I just read the Hawking interview > myself a few days ago. Sorry I can't give you the date of the issue, > because I just had a clip of the Hawking article -- not the whole > magazine, and I've passed the clip along to someone else. I'd venture > to say that it was sometime within the past two months, however. > > Carl Blesch Thanks to Carl Blesch for finding the magazine. The article is in the 16 August 1984 issue. The proteins discussed are hemoglobins and myoglobins, for which there exists abundant evidence that the more closely related a mammalian species is to humans (according to traditional taxonomy), the more similar these proteins are. For example, chimpanzee hemoglobin is nearly identical to human hemoglobin. An algorithm was applied to known sequences of hemoglobin from various species, and the result was that "man (the mammal) and chicken (the bird) were paired off as closest relatives, with the crocodile as the next nearest relative." It appears from the wording and the context of the sentence that only one mammalian and one avian hemoglobin were considered, but the sentence quoted above could have been worded better. In any case, it is demonstrably NOT true that human hemoglobin is more similar to chicken hemoglobin than it is to the hemoglobin of most other mammals. According to theory, the amount of dissimilarity between proteins in two different species is a measure of the length of time that has elapsed since they had a common ancestor. For example, even though kangaroos are more "primitive" than humans, EVOLUTION THEORY PREDICTS that the genetic distance of kangaroo hemoglobin from chicken hemoglobin should be about the same as that of human hemoglobin from chicken hemoglobin. Therefore it is legitimate to use any one mammalian species (e.g., human) as a proxy for them all when determining the relationships between large groups such as mammals, birds, crocodiles, turtles, amphibians, etc. Gish's claim was quite different, that for some proteins, the human version is closer to a chicken's than it is to a chimpanzee's, and for others, the human version is closer to a bullfrog's than to a chimpanzee's. So Dr. Gish is not let off the hook. As my original article pointed out, all he has to do to show that he was telling the truth is to (a) specify the sequences he claims exist, (b) state who did the sequencing and (c) state in which scholarly journal the sequences appear. -- "Biblical signoffs are for the smug." Bill Jefferys 8-% Astronomy Dept, University of Texas, Austin TX 78712 (USnail) {allegra,ihnp4}!{ut-sally,noao}!utastro!bill (uucp) bill%utastro.UTEXAS@ut-sally.ARPA (ARPANET)