Speaker 1: Welcome to brain stuff. From how stuff works, Hey, brain stuff,
Speaker 1: Lauren boge obamb here. Many of us have seen a
Speaker 1: turtle tucking itself into its protective shell, pulling in not
Speaker 1: only its four legs, but its head and tail as well.
Speaker 1: But while its shell shields a turtle's tender innards, it
Speaker 1: wasn't originally designed for that purpose, as an international group
Speaker 1: of scientists has found. Instead, they say the turtle shell
Speaker 1: most likely began as a digging tool. Tyler Lison, who
Speaker 1: is the lead author of the studying question and a
Speaker 1: paleontologist at the Denver Museum of Nature and Science, writes
Speaker 1: that when turtles first began developing shells a major evolutionary transition.
Speaker 1: The process included a broadening of the ribs. Broadened ribs
Speaker 1: made the turtles thoraxic region, or chest, more rigid. But
Speaker 1: the puzzling thing is that a rigid chest means it's
Speaker 1: harder for the animal to breathe easily or move swiftly,
Speaker 1: hardly changes that appear to enhance protective capabilities. But that's
Speaker 1: because initially, turtle shells made of more than fifty fused
Speaker 1: bones and their broad ribs were developed not for protection
Speaker 1: but to lend stability to the turtles so it could
Speaker 1: forcefully dig with its forelimbs. The researchers found being able
Speaker 1: to dig into the ground for food and shelter, they
Speaker 1: theorize allowed the turtles to move from the land into
Speaker 1: the water. This may have saved them in their early
Speaker 1: evolutionary history, specifically during the Permian Triassic extinction, the greatest
Speaker 1: mass extinction ever and one which was spurred by hot,
Speaker 1: dry weather. These insights came after two of the studies
Speaker 1: co authors discovered several specimens of a two hundred and
Speaker 1: sixty million year old turtle named Untosaurus africanus, the oldest
Speaker 1: to known partially shelled proto turtle. These specimens, along with
Speaker 1: another partially shelled turtle found by a young boy in
Speaker 1: South Africa, indicate turtles developed shells for use as digging aids.
Speaker 1: The scientists found similarities between these turtles and gopher tortoises,
Speaker 1: which use their heads and next to brace themselves while
Speaker 1: they dig with their forelimbs. The authors believe that the
Speaker 1: turtle's shell as a protective enclosure is an x adaption,
Speaker 1: meaning an evolutionary trait that originally served one function, but
Speaker 1: winds up serving another. Scientists have been arguing for at
Speaker 1: least two hundred years over whether the turtle's shell evolved
Speaker 1: from bony scales like those on an armadillo or certain lizards,
Speaker 1: or as part of its ribs broadening. Thanks to recent
Speaker 1: discovery of partially shelled stem turtles, it now seems that
Speaker 1: the latter theory is more likely. Today's episode was written
Speaker 1: by Melanie red Zeki McManus and produced by Tyler Clang.
Speaker 1: For more on this and lots of other evolutionarily advantageous topics,
Speaker 1: visit our home planet, how Stuff Works dot com