(urth) Mystery of Ascia

[entonio at gmail.com]

No dia 2011/01/22, às 13:11, Lee Berman <severiansola at hotmail.com>  
escreveu:
> *(the main reason humans and chimps cannot interbreed is not genetic  
> dissimilarity but chromosomal
> differences [different number]. I don't know if it has ever been  
> tried but if these species
> attempted to interbreed, the chromosomes would not match up properly  
> during fertilization to allow
> a viable embryo to form)

This is more properly the reason why mules are sterile - their  
maternal and paternal chromatids don't line up for meiosis. When  
populations become too dissimilar to interbreed, it's usually down to  
mechanics and gametal attachment incompatibility before chromosomal  
organisation. The latter of course matters because for a via le  
diploid organism about half the genome has to be deactivated, but  
there's some margin there (aneuploidy syndromes show some of the  
results when that's not possible).

But generally speaking I think these discussions are spurious. Again,  
observational data is usually solid. Explanations for it are ephemeral  
and one shouldn't count on them to understand the Books.