The present study reveals several interesting evolutionary observations on the HBB gene among the eutherian, dinosaurian and neopterygii taxa.
It is suggested that a number of events including gene conversion have occurred during evolution which has altered the clusters of [beta]-globin gene in specific ways in different eutherian (mammalian) orders.
This means that the platypus XY evolved independently of the eutherian XY and determines sex in a different, still unknown, way.
The platypus XY probably evolved independently of the eutherian XY.
The PEG10 gene arose from a retrovirus-like agent that inserted into mammalian DNA in an ancestor of marsupials and Eutherians
Egg-laying mammals, like the platypus and the echidna; marsupials, like the opossum and the wallaby; and all other mammals - called eutherians
- which include humans, dogs, mice, and giraffes.
For example, humans are included in the following nested clades (using the informal names): eukaryotes, animals, deuterostomes, vertebrates, gnathostomes, tetrapods, amniotes, mammals, eutherians
, primates, monkeys, apes, and great apes (see Dawkins, 2004 for more information on the ancestry of humans).