Welcome to brain Stuff from how stuff works. 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 published in the journal cell In indicates that the first walkers did it underwater. The Late Devonian vertebrate land invasion roughly three two million years ago was
a big deal in Earth's history. Previously confined to the ocean, our tetrapod forefathers took to the surface world and over the course of millions of years, traded fins and gills for limbs 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 about hard wear. 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 d 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 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 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 describe the skates movements, but 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 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 disorders.
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 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 motor neuron diseases such as amyotrophic lateral sclerosis or a LS. But as the saying goes, you have to crawl before you can walk or should we say, swim. Today's episode was written by Robert Lamb and produced by
Tristan McNeil. For more on this and lots of other topics on the go, visit our home planet, how Stuff Works dot com