Aliens in our midst

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… ​These similarities reflect two key principles of evolution, factors that are probably important on any world where life has emerged. The first is convergence: these far-flung branches of the evolutionary tree arrived at common designs for a nervous system because they each had to solve the same fundamental problems. The second is shared history: the idea that all of these differently built nervous systems shared at least some element of common origin. On our world, they each evolved from molecular building blocks that were forged in the physical and chemical environments of early Earth. ...