jho@ihu1m.UUCP (Yosi Hoshen) (09/04/85)
[I got a message that this article didn't make it to some nodes. Probably due to divine intervention. So here it is again] > I've seen a figure floating around that I'd like to hear some sort of > comment on. A guy with a masters in biochemistry from Michigan (I > think) gave the figure of 10^450 as the odds of life having been created > by evolution. I don't know how the guy came up with this number. To evaluate the application of probability to evolution, it is necessary to address two basic questions: (1) What is the probability that earth's particular life form has evolved? (2) What is the probability that any life form can evolve? One can make an assumption that all combinations of amino acids are equally probable, enumerate these combinations, and come up with a number, which is presumably 10^(-450). The assumption that all possible configurations are equally probable is probably not accurate, but let us accept it. So we can assume that the probability for question (1) is extremely small. However, to discuss the probability of evolution one has to answer question (2). And I don't think anyone can really answer this question. We don't know how many amino acid combinations would lead to life, and it is not known whether life's building blocks can only be based on the set of 20 amino acids, 4 RNA nucleotides, and 4 DNA nucleotides. Without answering this question, we cannot make any useful statement on the probability of evolution. If we somehow could determine the probability for question (2), say, to be 10^-8. This is a small probability value but not negligibly small. In this case it would not matter whether the probability for question (1) is 10^-450 or 10^-900, since it would be one of many possible outcomes. > A second question this guy brought up is that the basic formulation of > amino acids and proteins is possible and has been experimentally proven, > but according to him, the next step, the polypeptide chains (forgive any > glaring errors, I'm an expert in neither biology or chemistry) are almost > impossible to account for. Given the nature of the complexity of the > reactions (the need for a complex linking of singled handed chains in > order to carry genetic information) and the fact that most of the > reactions breakdown 10^5 times faster in water than they take place it > would seem difficult to assume organic evolution is how it actually > happened. Let me note: Proteins are polypetide chains. They are polymers of constructed out of 20 different amino acids. At present, the mechanism for the formation of the first self replicating molecules is not known. There are various assumptions related to this issue, but the mechanism is very speculative. It can be stated, that the formation of the first living organisms does not violate the laws of nature, (mechanics, electricity, thermodynamics, etc) even if the mechanism is unknown. The answers to the type of questions raised here requires more research in molecular biology. Although we have seen considerable advances in this field, it is still in its infancy. We have only partial answers to these questions, and probably many of these answers are inaccurate. Scientific theories are evolving constantly till they reach some kind of pseudo plateau. Take for example the atomic theory. The Thompson model viewed the atom as a cherry pie, where the nucleus occupies the entire volume of the atom while the electrons were stuck in it like cherries on a pie. This model answered many questions till Ratherford demonstrated by alpha particle experiments that the nucleus is very dense and occupies only small fraction of the atomic volume. In the past, natural events were attributed to supernatural forces (e.g. gods are responsible for thunder and lightning). As science progressed it turned out that there excellent naturalistic explanations for these phenomena. We should learn from our past experience and be patient, and not necessarily invoke the supernatural whenever we don't have an immediate answer. I don't think we want to return to the middle ages. -- Yosi Hoshen, AT&T Bell Laboratories Naperville, Illinois, Mail: ihnp4!ihu1m!jho