Recall that unicellular organisms evolved into multicellular organisms—not once, but many independent times. The driving forces that goaded that evolution, we think, were the capacity to escape predation, the ability to compete more effectively for scarce resources, and to conserve energy by specialization and diversification. Unitary blocks—cells—found mechanisms to achieve this specialization and diversification by combining common programs (metabolism, protein synthesis, waste disposal) with specialized programs (contractility in the case of muscle cells, or insulin-secreting capacity in
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