At Uncommon Descent, “niwrad” has posted a link to a Sequences Probability Calculator. This webserver allows you to set a number of trials (“chemical reactions”) per second, the number of letters per position (20 for amino acids) and a sequence length, and then it calculates how long it will take for you to get exactly that sequence. Each trial assumes that you draw a sequence at random, and success is only when you exactly match the target sequence. This of course takes nearly forever.
So in effect the process is one of random mutation without natural selection present, or random mutation with natural selection that shows no increase in fitness when a sequence partially matches the target. This leads to many thoughts about evolution, such as:
- Do different species show different sequences for a given protein? Typically they do, so the above scheme implies that they can’t have evolved from common ancestors that had a different protein sequence. They each must have been the result of a separate special creation event.
- If an experimenter takes a gene from one species and puts it into another, so that the protein sequence is now that of the source species, does it still function? If not, why are people so concerned about making transgenic organisms (they’d all be dead anyway)?
- If we make a protein sequence by combining part of a sequence from one species and the rest of that protein sequence from another, will that show function in either of the parent species? (Typically yes, it will).
Does a consideration of the experimental evidence show that the SPC fails to take account of the function of nearby sequences?
The author of the Sequences Probability Calculator views evolution as basically impossible. The SPC assumes that any change in a protein makes it unable to function. Each species sits on a high fitness peak with no shoulders. In fact, experimental studies of protein function are usually frustrating, because it is hard to find noticeable difference of function, at least ones big enough to measure in the laboratory.