Why can’t people regenerate limbs like salamanders?

Answering a reader's question, researchers explain that salamanders and zebrafish can regrow limbs, fins, and even damaged organs by forming a 'blastema,' a temporary cluster of cells that multiply and remember what tissue type to become. Humans manage smaller feats of regeneration, such as skin renewal, liver regrowth, and, in young children, regrown fingertip tissue, but not whole limbs.

Nerve signals appear essential to triggering regeneration, and scientists studying zebrafish have found that specialized reproductive structures on adult male fins actually suppress their regenerative ability, suggesting evolution sometimes trades regrowth capacity for other features. Labs are now probing whether the biological instructions behind animal regeneration could someday be activated in humans.

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