Roaches, that is: Many insects of today are tiny, compared to their ancient ancestors, but the biggest cockroaches that have ever lived are living in your kitchen today–they’re the size of steaks–and scientists are trying to figure out why. Many insects grow larger when the air is more oxygen-rich, because bugs breathe through their skin. The oxygen concentration of air on Earth has varied over the centuries, and so has the size of insects, but roaches defy this biological logic.
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