David Turell writes, under Definitions, 15.37, 10 April: "The tree [of life] does not 'advance' without the effects of selection, removing the less effective results of change in the organisms." - But there can be no 'advance' without the changes that selection works on. The two factors are interdependent. You go on to say: "The mystery comes from the fact that most beneficial mutations are recessive. Two organisms must have the same recessive mutation, then must meet each other and mate." Presumably you're talking here of reproductive changes, but that just doubles what for me is the overall mystery, which is how new organs can come into being through random mutations. Darwin did not tackle this problem ("how a nerve comes to be sensitive to light, hardly concerns us more than how life itself first originated") but since he repeatedly talks of the Creator, perhaps at that stage of his career it wasn't a problem for him. It is, though, for me! - You pointed out in your reply to whitecraw at 01.50, 7 April that "Darwin favored a gradual step by step change in organisms, and eventually a new species would appear." Whereas in fact: "New complex organisms appear suddenly, explosively, with no 'somewhat less' complex precursors." I'm not sure to what extent you and Darwin are talking about organs and/or organisms, although I suppose the one will lead to the other. Darwin says categorically: "If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down" (Difficulties on Theory). What I would like to know from our scientists is (a) what are the odds that random mutations can produce the first primitive but still astonishingly complex organs on which natural selection gets to work, and (b) is the evidence on organs in favour of Darwin's theory or not? But (c) even if it isn't, why does the theory "absolutely break down"? We are still confronted with the fact that we are here and we came much later than bacteria and millions of other species. We have so many features in common with comparatively recent preceding species that the "tree" of common descent still seems a logical historical pattern ... as does the process of natural selection ... even if organs came into being suddenly. But that remains the key mystery for me (after the origin of life itself): the emergence of complex new systems ... like David Turell's amazing example of blood clotting ... that must have been in working order right from the start or they wouldn't have survived.