On Fri, 22 Sep 2000 10:01:45 -0400, Ben Balzer <[log in to unmask]> wrote: >.. As for U-turns- they are very difficult- as you >say, it is easy to lose a gene, but to reproduce it is awesomely difficult. > >For a 30 amino acid protein (takes a 90 DNA sequence) to be randomly >produced - with 4 different DNA codes, this makes 4 to the power of 90= 10 >to the 54 = a billion billion billion billion billion billion. Makes the >odds of being hit by an asteroid look good. It appears to me that most genetic changes change more the adjustments of shape and extent in which already existing metabolic mechanisms are used. We share 84% of our genes with cows. We have identical genes to over 93% with mice and some 97% idendity with chimps. The primary mammal metabolism, particularly which enzymes are used, which nutrition pathways are possible, how cells are built and destructed is not so much different. But some genes -which weren't necessary for long- may have been *lost* during the time. Like the ability to synthesize Vitamin C or some function with folacin (as you noted). As you outline, the probability that a *new* enzyme or smallest components of our digestion apparatus emerge, is *very* small. What does differ significantly is the size of various organs. Brain of course which increased our intellect and glucose requirement. Muscles, liver, kidney, pancreas, gall have smaller differences and tend to adapt short term and to individual needs. The length of various parts of the gut (intestine, ileum, stomach) have been stressed much by both the veg*an and meatatarian believers. As gut length doesn't change during the life gorillas, cows, cats and humans are variedly fit for varying food sources. A longer gut is capable to house more of the symbiont bacteria which break down cellulose walls. Longer guts exploit heavy cellulose food (like leaves) better than shorter guts. Shorter guts protect better from putrefying bacteria in quick digested food. I leave it to scientists or to some charts where humans should be classified in. Humans are somewhere between gorilla and cat, but much nearer to gorillas as far as i recall. Maybe someone can provide a chart with gut lengths of more animals as just wolfs and sheep (e.g. cats and chimps). But in general all these animals (and our animal body) are capable to rely on the most food sources. Cows *can* be fed meat (and are), chimps eat baby monkeys. As a conclusion of all this, I think it's wise to keep more attention on the *real* physiological constraints. 1.The essentials (vitamins) are known most effective constraints. The most striking field in this area are for me the energy vitamins - the vitamins necessary to metabolize food fuel (Vitamin b1, b2, b3). They are *guaranteed* in all paleolithic and pre-industrial food items. And unavailable in *most* food items of today. 2.The varying capability to cope with disturbing substances (toxins) too. Cats are capable to deal with purin and botulinus, humans less or not. Some birds can easily deal with phytin, humans much less. Btw.... this was from the paleo-religion thread.... Something I'd like to say. I personally never felt a big contradiction between creationists and evolutionists. If God has created the earth why shouldn't he do it by means of evolution. And the 7 days... What is a day of God anyway? Especially before the sun and earth was created, which defines a "day". Cheers Amadeus S.