Monthly Archives: January 2013

Is evolution of proteins impossible?

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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.

ID, ENCODE and the Happy Isles of Fitness

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As Neil Rickert was foolish enough to grant me posting rights, I had better take advantage of the offer before the sysops sensibly change their minds.

Consider an argument used consistently by the ID community: that the natural processes of genetic mutation and environmental selection acting upon the resultant variation are incapable of generating speciation.

Their recurring metaphor is of improbable islands of fitness separated by unbridgeable seas of non-functionality. Even if the hill-climbing capability of “random mutation plus natural selection” is real (and even incorporating unselected allele frequency changes), evolution can’t work because “you can’t get there from here”. For brevity, let me acronymise this argument as CANTSWIM.

CANTSWIM has a great many shortcomings as a metaphor for how evolutionary processes actually work, and you don’t need me to enumerate them. But let me hand over the title deeds to the evolutionary farm, and assume that CANTSWIM is factual.

At the same time, the ID community has adopted the claim made by the leadership of the ENCODE program that >80 per cent of the human genome is functional. The devil, of course, is in the detail of how “functional” is defined.

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David B. Hart and the problem of evil

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Why do evil and suffering exist if the world is presided over by a God who is all-knowing, all-powerful and perfectly loving? That is the “problem of evil” in a nutshell.  In an earlier post (and in the comments) I explained and argued against two common theistic responses to the problem of evil.  Now I’ll tackle a third response from Eastern Orthodox theologian David Bentley Hart.

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