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Van Valens ‘law’

Van Valen's ‘law’ When plotted as cumulative curves on a logarithmic scale, the duration frequencies of many species tend to show a more or less straight-line relationship with time. In effect, taxa generally become extinct regardless of their age. Duration frequencies vary greatly among different groups, e.g. on average, bivalve genera last ten times longer than mammalian genera. The ‘law’ is named after L. Van Valen, who proposed it in 1973.

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