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

Some fish that strut the seafloor share a common ancestor with humans, so researchers are hoping that studying these fish could help us understand how we walk. Learn how in this classic episode of BrainStuff, based on this article: https://animals.howstuffworks.com/extinct-animals/ancient-fish-strutted-seafloor-before-land-animals.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of I Heart Radio. Hey
brain Stuff, I'm Lauren vogel Bomb and this this is
a classic episode from our archives. We humans tend to
think of ourselves as being at the top of the
evolutionary ladder, but the truth is that we exist on
more of a continuum alongside countless other creatures with features

(00:23):
worth exploring. One that surprised us is how much fish
can teach us about walking. Hey, brain Stuff, Lauren vogel Bomb. Here,
where did you get that walk? Like many people, you
might guess our vertebrate gate originates with the first backboned
creatures to scramble out of the sea, but a study

(00:43):
published in the journal Cell indicates that the first walkers
did it underwater. The Late Devonian vertebrate land invasion roughly
three eight two million years ago, was a big deal
in Earth's history. Previously confined to the ocean, our tetrapod
forefathers took to the surface swirld and over the course
of millions of years, traded fins and gills for limbs

(01:04):
and lungs. A tetrapod, by the way, just means vertebrates
with two pairs of limbs. The remarkable thing, says the
team of researchers, is that the neural circuits involved an
ambulatory limb control were already established millions of years before
the first tetrapod strutted its stuff. In other words, much
of the software was in place well before the walk

(01:25):
about hardware. The researchers studied the neural circuitry of the
little skate. This cartilaginous fish might not be much to
look at, but it's considered one of the most primitive
vertebrates alive today. Travel back roughly four and twenty million
years and you'll find a common ancestor of both skates
and tetrapods. The little skate is also interesting because it's

(01:46):
one of several ambulatory fish that walk across the sea floor.
The skate uses its large pectoral fins to swim and
smaller pelvic fins to walk with alternating left right motions,
much like the gate of a land animal. This similarity
impressed the researchers, but these similarities would go beyond movement.
The team employed RNA sequencing to study the expressed genes

(02:07):
in these skates motor neurons. Many of these genes pop
up in mammals as well, and that includes neural subtypes
involved in the muscle control of bending and straightening limbs. This,
according to the study findings, constitutes a conserved genetic program
for walking. Study co author Jeremy S. Dayson says that
neither swimming nor walking accurately described the skates movements, but

(02:30):
perhaps this isn't too surprising given the human centric nature
of our language, he said via email. The skate ray
mode I would call ambulatory swimming, whereas the axial tail
based is more like spinal swimming. The ambulatory swimming mode
is really the one which made walking possible in both
skates and tetrapods. The study sheds light on the underwater

(02:53):
history of walking, but the researchers hope that it will
lead to an improved understanding of motor neurons and even
the treatment of human neurological to orders. Jason stresses that
while the neural complexity of higher organisms does hinder our
study of animals such as mice, the little skates archaic
simplicity makes it a perfect starting point. He said, I
think one of the advantages of studying neural circuits and

(03:14):
skates is that they can accomplish this behavior using a
relatively simple set of connections between neurons and muscle, we
hope we can exploit the simplicity to understand the basic
architecture of the circuits controlling walking. The exact wiring of
these circuits is still not fully understood in humans or
other tetrapods, but such knowledge could one day aid in
the treatment and repair of human spinal cord injuries and

(03:35):
motor neuron diseases such as a myotrophic lateral sclerosis or
a l S. But as the saying goes, you have
to crawl before you can walk, or should we say swim.
Today's episode was originally produced by Tristan McNeil and is
based on the article ain't fish strutted the sea floor

(03:56):
before land Animals? On How stuff Works dot Com, written
by rob Bert Lamb. To hear more from Robert about
things strutting to see floor, check out his weird fiction
podcast mini series The second oil Age. You'll hear a
familiar voice in the first episode. Brain Stuff is production
of I Heart Radio in partnership with how Stuffworks dot
Com and is produced by Tyler clang Or more podcasts

(04:18):
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