At least two of the extinct, ancient humans had type O blood, making them the "universal donor", according to a new genetic analysis of remains of 45,000 year old individuals.

That's not to say all Neanderthals were type O--others may have also boasted genes for the A and B blood types, which encode enzymes that sprinkle red blood cells with two different sugar molecules. [Any connection to susceptibility to diabetes?]

Previous research indicated that this mutation occurred about a million years ago, probably in the hominid common ancestor of humans and Neanderthals. Natural selection may sometimes favour a specific blood type. Type O seems to protect against malaria, for example [I have natural immunity to smallpox too], but makes people more susceptible to bacteria that cause cholera and stomach ulcers.

The other group with a high O frequency today is native Americans. They're not closely related, but they may have experienced similar environments to the extent that they might have been isolated from diseases that came from Africa and South Asia.

This information is from the New Scientist online journal. Makes me wonder if I'm a throwback. We have Native American ancestry on my mother's side of the family. Maybe we can even claim a Neanderthal connection. Now that's a throwback!