Speaker 1: Welcome to brain Stuff from how stuff works. Hey, brain stuff,
Speaker 1: Lauren Vogel bomb here, where did you get that walk?
Speaker 1: Like many people, you might guess our vertebrate gate originates
Speaker 1: with the first backboned creatures to scramble out of the sea,
Speaker 1: but a study published in the journal cell In indicates
Speaker 1: that the first walkers did it underwater. The Late Devonian
Speaker 1: vertebrate land invasion roughly three two million years ago was
Speaker 1: a big deal in Earth's history. Previously confined to the ocean,
Speaker 1: our tetrapod forefathers took to the surface world and over
Speaker 1: the course of millions of years, traded fins and gills
Speaker 1: for limbs and lungs. A tetrapod, by the way, just
Speaker 1: means vertebrates with two pairs of limbs. The remarkable thing,
Speaker 1: says the team of researchers, is that the neural circuits
Speaker 1: involved an ambulatory limb control were already established millions of
Speaker 1: years before the first tetrapod strutted its stuff. In other words,
Speaker 1: much of the software was in place well before the
Speaker 1: walk about hard wear. The researchers studied the neural circuitry
Speaker 1: of the little skate, This cartilaginous fish might not be
Speaker 1: much to look at, but it's considered one of the
Speaker 1: most primitive vertebrates alive today. Travel back roughly four d
Speaker 1: and twenty million years and you'll find a common ancestor
Speaker 1: of both skates and tetrapods. The little skate is also
Speaker 1: interesting because it's one of several ambulatory fish that walk
Speaker 1: across the sea floor. The skate uses its large pectoral
Speaker 1: fins to swim and smaller pelvic fins to walk with
Speaker 1: alternating left right motions, much like the gate of a
Speaker 1: land animal. This similarity impressed the researchers, but these similarities
Speaker 1: would go beyond movement. The team employed RNA sequencing to
Speaker 1: study the expressed genes in these skates motor neurons. Many
Speaker 1: of these genes pop up in mammals as well, and
Speaker 1: that includes neural subtypes involved in the muscle control of
Speaker 1: bending and straightening limbs. This, according to the study findings,
Speaker 1: constitutes a conserved genetic program for walking. Study co author
Speaker 1: Jeremy S. Dayson says that neither swimming nor walking accurately
Speaker 1: describe the skates movements, but perhaps this isn't too surprising
Speaker 1: given the human centric nature of our language. He said,
Speaker 1: via email. The skate ray mode I would call ambulatory swimming,
Speaker 1: whereas the axial tail based is more like spinal swimming.
Speaker 1: The ambulatory swimming mode is really the one which made
Speaker 1: walking possible in both skates and tetrapods. The study sheds
Speaker 1: light on the underwater history of walking, but the researchers
Speaker 1: hope that it will lead to an improved understanding of
Speaker 1: motor neurons and even the treatment of human neurological disorders.
Speaker 1: Jason stresses that while the neural complexity of higher organisms
Speaker 1: does hinder our study of animals such as mice, the
Speaker 1: little skates archaic simplicity makes it a perfect starting point.
Speaker 1: He said, I think one of the advantages of studying
Speaker 1: neural circuits and skates is that they can accomplish this
Speaker 1: behavior using a relatively simple set of connections between neurons
Speaker 1: and muscle. We hope we can exploit the simplicity to
Speaker 1: understand the basic architecture of the circuits controlling walking. The
Speaker 1: exact wiring of these circuits is still not fully understood
Speaker 1: in humans or other tetrapods, but such knowledge could one
Speaker 1: day aid in the treatment and repair of human spinal
Speaker 1: cord injuries. And motor neuron diseases such as amyotrophic lateral
Speaker 1: sclerosis or a LS. But as the saying goes, you
Speaker 1: have to crawl before you can walk or should we say, swim.
Speaker 1: Today's episode was written by Robert Lamb and produced by
Speaker 1: Tristan McNeil. For more on this and lots of other
Speaker 1: topics on the go, visit our home planet, how Stuff
Speaker 1: Works dot com