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 10 times longer than mammalian genera). The ‘law’ is named after its discoverer, L. Van Valen.

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. The ‘law’ is named after its discoverer, L. Van Valen.