Are there evolutionary reasons for reproduction?

As well as making an argument which basically makes no sense, since there can be no evolution without some sort of self-replicating entity, you are making a whole lot of totally unwarranted assertions.The species which adopt your favoured strategy of never reproducing tend to die out very quickly, funny that. Species which adopt the arguably more wasteful reproducing strategy tend to increase in number comparatively. The advantage of reproduction is that the numbers of a particular type increase so they are less likely to be totally extinguished by some chance event.The waste is allowable since there is a continuous influx of energy into the system. If there were only a very limited amount of energy available then a more cautious strategy might be neccessary. Indeed we see trade offs in how much investment an organism makes into its offspring and the number of offspring it has, so limited resources clearly do play their part.I really hope this is some sort of joke.TTFN,WK

Should we also assume that you didn't know such mechanisms are far from perfect and that despite them there is a wealth of hard genetic data showing that genes are continuously being duplicated within the human population (Sharp et al., 2005; Bailey et al., 2008; Zhang et al., 2009). Even between monozygotic twins there are instances of copy number variation (Bruder at al., 2008). This is not really correct, both purines (A,G) and pyrimidines (C,T,U) can be produced from prebiotic precursors without the need for any enzymes, as can ribose. These elements can, in the case of the purines at least subsequently form ribonucleic acids, but these are not stable.There are however a number of alternative chemical routes to RNA production which have yet to be properly explored, for a review of a number of these see Anastasi et al. (2007). So chemical reactions do exist to produce and oligomerise RNA nucleotides, but as yet a fully plausible set of prebiotic conditions which would allow them is not apparent. One paper from last year has shown some success in producing activated pyrimidine ribonucleotides from prebiotic 'feedstock' (Powner et al., 2009).TTFN,WKEdited by Wounded King, : No reason given.Edited by Wounded King, : No reason given.Edited by Wounded King, : Added copy number variation material.

Good for you, but their 'near perfect' is still far from perfect, if you see what I mean. As an error correcting mechanism it is very efficient, but the sheer volumes of genetic material involved mean that mutations are an inevitable result. There is plenty of research on the mutation rate, if you can show me any that says the mutation rate is 0 I'll be very surprised. In fact in Wikipedia the very words 'near perfect' are a link to the wiki article on mutation. Wow, you just totally changed the premise of your argument, nice goal post shift. The most commonly posited explanation for this is that life arose in the oceans, where a depth of ~30 metres would reduce the radiative effects to equivalent to those of the modern day. Did you miss the paper I linked to discussing pyrimidine synthesis? Well this is just nonsense, base pairing is a phenomenon of higher structural levels for RNA. Single stranded RNA doesn't need base pairing so any number of sequences composed of sequences of A's and G's is possible. Or is your argument that without a complementary partner there will be no folding to functional tertiary structures like hairpins? That might be a valid argument, if it were true that pyrimidines couldn't be formed, which it isn't. Not really, you claimed that no chemical reactions to produce ribonucleic acids existed that didn't require enzymes. I gave you a reference to a paper full of non-enzymatic chemical routes, as well as one paper showing such a route in operation. So your claim is false, now you are switching claims, no one is going to be fooled by this into accepting that your initial claim was true.TTFN,WK

Hasn't this exact question been answered for you just a post or two ago?You need to learn that oxygen atoms behave differently in different molecular compounds. Not all oxygen species are as reactive as each other.Atmospheric oxygen tends to have more reactive species due to ionising radiation. As has been pointed out the prebiotic earth essentially had no atmospheric oxygen and water is quite effective at attenuating ionising radiation. So there would not be a high proportion of toxic reactive oxygen species.To some extent this also depends on the exact abiogenesis scenario you are discussing as deep sea vents are obviously even more protected while a surface pool scenario might allow a substantial exposure to ionising radiation but may not consist principally of water.It is also worth noting that a number of proposed abiogenetic pathways rely on ionising radiation, in the form of UV, for certain reactions to occur.TTFN,WK

I think what Barbara is asking is how the, as yet unidentified, retrovirally derived gene maps to a robust phylogenetic tree. Does all the members of our best guess tree showing the placental mammals have this sequence? Are there clades or grades within the placental mammals defined by specific retrovirally derived genes?I'd suggest that a better place for this discussion is the Retroviral role in placental evolution thread I opened for this very topic, where we have still as yet to actually identify what the retroviral gene in question is supposed to be.TTFN,WK