WEBVTT - BrainStuff Classics: What Can We Learn from Fish about Walking?

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<v Speaker 1>Welcome to brain Stuff production of I Heart Radio. Hey

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<v Speaker 1>brain Stuff, I'm Lauren vogel Bomb and this this is

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<v Speaker 1>a classic episode from our archives. We humans tend to

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<v Speaker 1>think of ourselves as being at the top of the

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<v Speaker 1>evolutionary ladder, but the truth is that we exist on

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<v Speaker 1>more of a continuum alongside countless other creatures with features

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<v Speaker 1>worth exploring. One that surprised us is how much fish

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<v Speaker 1>can teach us about walking. Hey, brain Stuff, Lauren vogel Bomb. Here,

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<v Speaker 1>where did you get that walk? Like many people, you

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<v Speaker 1>might guess our vertebrate gate originates with the first backboned

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<v Speaker 1>creatures to scramble out of the sea, but a study

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<v Speaker 1>published in the journal Cell indicates that the first walkers

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<v Speaker 1>did it underwater. The Late Devonian vertebrate land invasion roughly

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<v Speaker 1>three eight two million years ago, was a big deal

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<v Speaker 1>in Earth's history. Previously confined to the ocean, our tetrapod

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<v Speaker 1>forefathers took to the surface swirld and over the course

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<v Speaker 1>of millions of years, traded fins and gills for limbs

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<v Speaker 1>and lungs. A tetrapod, by the way, just means vertebrates

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<v Speaker 1>with two pairs of limbs. The remarkable thing, says the

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<v Speaker 1>team of researchers, is that the neural circuits involved an

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<v Speaker 1>ambulatory limb control were already established millions of years before

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<v Speaker 1>the first tetrapod strutted its stuff. In other words, much

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<v Speaker 1>of the software was in place well before the walk

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<v Speaker 1>about hardware. The researchers studied the neural circuitry of the

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<v Speaker 1>little skate. This cartilaginous fish might not be much to

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<v Speaker 1>look at, but it's considered one of the most primitive

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<v Speaker 1>vertebrates alive today. Travel back roughly four and twenty million

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<v Speaker 1>years and you'll find a common ancestor of both skates

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<v Speaker 1>and tetrapods. The little skate is also interesting because it's

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<v Speaker 1>one of several ambulatory fish that walk across the sea floor.

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<v Speaker 1>The skate uses its large pectoral fins to swim and

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<v Speaker 1>smaller pelvic fins to walk with alternating left right motions,

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<v Speaker 1>much like the gate of a land animal. This similarity

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<v Speaker 1>impressed the researchers, but these similarities would go beyond movement.

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<v Speaker 1>The team employed RNA sequencing to study the expressed genes

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<v Speaker 1>in these skates motor neurons. Many of these genes pop

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<v Speaker 1>up in mammals as well, and that includes neural subtypes

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<v Speaker 1>involved in the muscle control of bending and straightening limbs. This,

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<v Speaker 1>according to the study findings, constitutes a conserved genetic program

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<v Speaker 1>for walking. Study co author Jeremy S. Dayson says that

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<v Speaker 1>neither swimming nor walking accurately described the skates movements, but

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<v Speaker 1>perhaps this isn't too surprising given the human centric nature

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<v Speaker 1>of our language, he said via email. The skate ray

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<v Speaker 1>mode I would call ambulatory swimming, whereas the axial tail

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<v Speaker 1>based is more like spinal swimming. The ambulatory swimming mode

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<v Speaker 1>is really the one which made walking possible in both

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<v Speaker 1>skates and tetrapods. The study sheds light on the underwater

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<v Speaker 1>history of walking, but the researchers hope that it will

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<v Speaker 1>lead to an improved understanding of motor neurons and even

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<v Speaker 1>the treatment of human neurological to orders. Jason stresses that

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<v Speaker 1>while the neural complexity of higher organisms does hinder our

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<v Speaker 1>study of animals such as mice, the little skates archaic

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<v Speaker 1>simplicity makes it a perfect starting point. He said, I

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<v Speaker 1>think one of the advantages of studying neural circuits and

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<v Speaker 1>skates is that they can accomplish this behavior using a

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<v Speaker 1>relatively simple set of connections between neurons and muscle, we

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<v Speaker 1>hope we can exploit the simplicity to understand the basic

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<v Speaker 1>architecture of the circuits controlling walking. The exact wiring of

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<v Speaker 1>these circuits is still not fully understood in humans or

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<v Speaker 1>other tetrapods, but such knowledge could one day aid in

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<v Speaker 1>the treatment and repair of human spinal cord injuries and

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<v Speaker 1>motor neuron diseases such as a myotrophic lateral sclerosis or

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<v Speaker 1>a l S. But as the saying goes, you have

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<v Speaker 1>to crawl before you can walk, or should we say swim.

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<v Speaker 1>Today's episode was originally produced by Tristan McNeil and is

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<v Speaker 1>based on the article ain't fish strutted the sea floor

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<v Speaker 1>before land Animals? On How stuff Works dot Com, written

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<v Speaker 1>by rob Bert Lamb. To hear more from Robert about

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<v Speaker 1>things strutting to see floor, check out his weird fiction

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<v Speaker 1>podcast mini series The second oil Age. You'll hear a

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<v Speaker 1>familiar voice in the first episode. Brain Stuff is production

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<v Speaker 1>of I Heart Radio in partnership with how Stuffworks dot

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<v Speaker 1>Com and is produced by Tyler clang Or more podcasts

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<v Speaker 1>from my heart Radio, visit the iHeart Radio app, Apple podcasts,

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