ScienceDaily (Oct. 31, 2012) — Since
the age of dinosaurs, most species of day-active mammals have retained the
imprint of nocturnal life in their eye structures. Humans and other anthropoid
primates, such as monkeys and apes, are the only groups that deviate from this
pattern, according to a new study from The University of Texas at Austin and
Midwestern University.
The findings, published in a
forthcoming issue of Proceedings of the Royal Society B, are the first to
provide a large-scale body of evidence for the "nocturnal bottleneck
theory," which suggests that mammalian sensory traits have been profoundly
influenced by an extended period of adaptation to nocturnality during the
Mesozoic Era. This period lasted from 250 million years ago to 65 million years
ago.
To survive in the night,
mammals had a host of visual capabilities, such as good color vision and high
acuity, which were lost as they passed through the nocturnal
"bottleneck."
"The fact that nearly all
living mammals have eye shapes that appear 'nocturnal' by comparison with other
amniotes [mammals, reptiles and birds] is a testament to the strong influence
that evolutionary history can have on modern anatomy," says Chris Kirk,
associate professor of anthropology at The University of Texas at Austin.
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