Publication: Long-period astronomical forcing
of mammal turnover
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Publication Date
2006
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Nature Publishing Group
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Abstract
Mammals are among the fastest-radiating groups, being characterized
by a mean species lifespan of the order of 2.5 million years
(Myr)1,2. The basis for this characteristic timescale of origination,
extinction and turnover is not well understood. Various studies
have invoked climate change to explain mammalian species
turnover3,4, but other studies have either challenged or only
partly confirmed the climate–turnover hypothesis5–7. Here we
use an exceptionally long (24.5–2.5Myr ago), dense, and welldated
terrestrial record of rodent lineages from central Spain,
and show the existence of turnover cycles with periods of
2.4–2.5 and 1.0Myr. We link these cycles to low-frequency
modulations of Milankovitch oscillations8, and show that
pulses of turnover occur at minima of the 2.37-Myr eccentricity
cycle and nodes of the 1.2-Myr obliquity cycle. Because obliquity
nodes and eccentricity minima are associated with ice
sheet expansion and cooling and affect regional precipitation, we
infer that long-period astronomical climate forcing is a major
determinant of species turnover in small mammals and probably
other groups as well.