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New Clues to Why Size Equals Destiny

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Science  04 Jun 1999:
Vol. 284, Issue 5420, pp. 1607-1609
DOI: 10.1126/science.284.5420.1607

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Dueling theories aim to explain why larger organisms tend to live longer; both conclude that the physics of nutrient distribution is key. On page 1677, a research team proposes that the so-called quarter-power law--which states that life-span tends to lengthen in proportion to the quarter power of an animal's body weight--derives from the physical constraints of an ideal system for distributing nutrients, whether it's the blood conduits running through our body or the vascular network nourishing a plant. An alternative theory from a second group (Nature, 13 May, p. 130) differs in details but comes to the same conclusion: The constraints on life-span and metabolism lie within an organism and have nothing to do with outward size and shape.