How can your slow continent of flesh adapt to create specific defenses for each of the millions of different microorganisms and the millions more that don’t even exist yet? The answer is as simple as it is baffling: The immune system does not so much adapt to new invaders as it already was adapted when you were born. It comes preinstalled with hundreds of millions of different immune cells—a few for every possible threat that you could possibly encounter in this universe. Right now you have at least one cell inside you that is a specific weapon against the Black Death, any variant of the flu,
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