In elementary school in California in the 60's, I was shown an instructional film called "Hemo the Magnificent". I loved it, and there was this one memorable scene: The animated character "Hemo" (representing some quasi-mythical, Greek-like conception of the "god of blood" or something) is conversing with a real-person "scientist" and a "journalist", and poses a series of questions to challenge mankind's current knowledge and wisdom. One question is: "What other substance in the world is closest to blood?" (or words to that effect). The scientist's immediate and confident answer (causing the journalist to drop his jaw): "Sea water."
The subsequent evolutionary explanation made perfect sense. But there's this other thing about blood (maybe it was explained elsewhere in that film and I missed or forgot it): what about our differences in blood type (A-pos, O-neg, ...)? What might have caused these differences to arise? To what extent are these differences reflected in other mammalian species? What (if anything) do they tell us about human origins and/or development? Do they interact in any way with natural selection, and if so, how?
Elementary school films turned out to be my only exposure to formal instruction in biology (or chemistry), so I apologize in advance for asking questions that are naive/vague, and for not doing very much googling on my own yet. I would be grateful for layman-term descriptions where possible, though I promise to do the necessary wikipedia lookups for technical terms (other instructional links will be appreciated).
Since blood types are of course never mentioned in the Bible, I don't expect Creationists to have much to say on the topic, though if there are any "non-Biblical" ID-ists who would like to postulate some relevant "design features" regarding blood-type differences, that's bound to be interesting.
autotelic adj. (of an entity or event) having within itself the purpose of its existence or happening.
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