Many of you will have seen the news reports last week about the amazing new discovery that the duck-billed platypus has not two (like humans) but ten sex chromosomes. So human females are XX and human males are XY (and yes, some people do get born with XXY) but a platypus is what, ABCDEFGHIJ?

Well, I was too busy to follow it up at the time, but now I’m starting to, and like most science stories in the media this not really something new. The platypus has five pairs of sex chromosomes (sort of XXXXXYYYYY). Its close relative, the echidna, has something very similar. Here, for example, is a paper from 2007 on the subject. Clearly the prospects for intersex monotremes are enormous, though as with humans such developments are very rare. What really interested me, however, was finding out that birds have an entirely different system of sex chromosomes to mammals. Birds, apparently, are either ZZ or ZW. Nature, as usual, is far more weird and wonderful that most people are aware.

And just to prove how weird and wonderful it is, here is Jennifer Ouellette on why a platypus isn’t a chimera but some humans are.