From “Platypus helps shed new light on mammalian evolution” (Physorg, Oct 20), we learn:
“We have seen many genome sequencing projects over the past decade but until now nobody has tackled the big question of how the regulation of genes has changed during 200 million years of mammalian evolution,” Dr Grützner says.
“In some tissues more changes have occurred than in others. For example, in the brain we observed fewer changes compared to the testes, suggesting that changes were more subtle in the brain.”
Ours sex chromosomes are said to have emerged after the monotremes separated from other mammals. Why? From New Scientist
But in platypuses, XXXXXXXXXX creates a female, while XYXYXYXYXY creates a male. In other words, rather than a single chromosome pair, platypuses have a set of ten-chromosomes that determine their sex.
Not the usual XX vs. XY stuff of mammals.
Here’s a look at the platypus up close: