My friend David Haig who happens to be working on a general paper, of which this is a part, points out that reptiles have a natural protection against endoviruses because a fertilized egg goes through at least ten cell divisions before becoming transcriptionally active, sometimes many more, while in marsupials and placentals cells are active at the first or second cell stage. Since retroviruses require an RNA intermediate, delayed zygotic transcription is a good defense against retroviruses. Why then did mammals give up this excellent defense? Perhaps, as he argues, because of dear old parent-offspring conflict, where the offspring benefits from early transcription in its conflict with mother. No such conflict in reptiles.

My friend David Haig who happens to be working on a general paper, of which this is a part, points out that reptiles have a natural protection against endoviruses because a fertilized egg goes through at least ten cell divisions before becoming transcriptionally active, sometimes many more, while in marsupials and placentals cells are active at the first or second cell stage. Since retroviruses require an RNA intermediate, delayed zygotic transcription is a good defense against retroviruses. Why then did mammals give up this excellent defense? Perhaps, as he argues, because of dear old parent-offspring conflict, where the offspring benefits from early transcription in its conflict with mother. No such conflict in reptiles.

Thank you very much Robert for that useful information

My understanding is that there would probably be no marsupials, or especially mammals, without endogenised retroviruses (ERVs) as ERVs seemed to be essential for the evolution of that amazing mammalian novelty the placenta. Perhaps we owe our existence to ancient endogenised retroviruses!

I think you over-emphasise conflict Robert. I think 'selfish gene' is a rather silly metaphore. Genes 'co-operate' (another metaphore) a lot , else we wouldn't be here. One author calls them 'genial genes'! I think perhaps that a gene is just a gene,  not selfish, not genial, just a gene.  

Now you are getting stupid. i do not use the term "selfish gene", never have and did not it in my communication with you; if you wish to argue about the term, i suggest you contact Richard Dawkins

yes, indeed, endogenous retroviruses have been co-adapted in placental evolution at least four times independently, probably because of their ability to break down cell walls, so that a placental wall of 1000 cells has no internal boundaries constraining function—but to then say that there would not be marsupials or placentals because of this fact is feeble on its face—multiple other avenues exist for the evolution of placentae, whether with cell boundaries or without

then you turn around and tell me "Robert" that you think i over-emphasize conflict, to which i say, "f… you buddy"—we are not friends or companions, you are the kind of idiot that wants to take an initially beneficial interaction down the road to insult

so you are unaware of the enormous internal genetic conflict within all eukaryotes? are you aware that your paternal genes are in conflict with your maternal ones? do you actually think that transposable elements transposing within you is good for you?—exactly how f…. ignorant are you ?  why not download from roberttrivers.com a complete pdf of my book with Austin Burt on Genes in Conflict: the Biology of Selfish Genetic Elements (Harvard,, 2006)—you will save the cost of the book but to gain a benefit you will actually have to read it and, yes, concentrate and learn, some of it is complex

yes i mentioned parent-offspring CONFLICT—what kind of an idiot are you, have you had children, were you not raised by parents, are you completely unaware of conflict in this relationship, and its long-term evolutionary importance, including genomic imprinting and numerous counter-adaptations on each side? if you want to hold strong, be advised that there are now 3255 references to the paper in Google Scholar, so you have your work cut out for you

There is absolutely no reason to use such insulting language Robert. Just make your points calmly and clearly, then I will listen and consider. If I agree, you are happy, if I don't agree then that's just how it is. Science is not dogma. I own a copy ofyour book, and did read it a long time ago. 

you are the one that started with stupid insults; i could not care less whether you agree or disagree, my happiness has nothing to do with you

I did not insult you in any way. Let's just leave it at that.