1 00:00:01,920 --> 00:00:06,360 Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey 2 00:00:06,440 --> 00:00:09,360 Speaker 1: brain Stuff, I'm Lauren vogel Bomb and this this is 3 00:00:09,400 --> 00:00:13,319 Speaker 1: a classic episode from our archives. We humans tend to 4 00:00:13,400 --> 00:00:15,600 Speaker 1: think of ourselves as being at the top of the 5 00:00:15,640 --> 00:00:19,079 Speaker 1: evolutionary ladder, but the truth is that we exist on 6 00:00:19,320 --> 00:00:23,720 Speaker 1: more of a continuum alongside countless other creatures with features 7 00:00:23,720 --> 00:00:28,120 Speaker 1: worth exploring. One that surprised us is how much fish 8 00:00:28,320 --> 00:00:33,880 Speaker 1: can teach us about walking. Hey, brain Stuff, Lauren vogel Bomb. Here, 9 00:00:34,400 --> 00:00:37,479 Speaker 1: where did you get that walk? Like many people, you 10 00:00:37,600 --> 00:00:41,199 Speaker 1: might guess our vertebrate gate originates with the first backboned 11 00:00:41,240 --> 00:00:43,920 Speaker 1: creatures to scramble out of the sea, but a study 12 00:00:43,920 --> 00:00:47,639 Speaker 1: published in the journal Cell indicates that the first walkers 13 00:00:47,760 --> 00:00:51,960 Speaker 1: did it underwater. The Late Devonian vertebrate land invasion roughly 14 00:00:52,000 --> 00:00:54,880 Speaker 1: three eight two million years ago, was a big deal 15 00:00:54,920 --> 00:00:58,640 Speaker 1: in Earth's history. Previously confined to the ocean, our tetrapod 16 00:00:58,680 --> 00:01:01,520 Speaker 1: forefathers took to the surface swirld and over the course 17 00:01:01,560 --> 00:01:04,600 Speaker 1: of millions of years, traded fins and gills for limbs 18 00:01:04,600 --> 00:01:07,600 Speaker 1: and lungs. A tetrapod, by the way, just means vertebrates 19 00:01:07,640 --> 00:01:11,240 Speaker 1: with two pairs of limbs. The remarkable thing, says the 20 00:01:11,319 --> 00:01:14,560 Speaker 1: team of researchers, is that the neural circuits involved an 21 00:01:14,560 --> 00:01:18,559 Speaker 1: ambulatory limb control were already established millions of years before 22 00:01:18,600 --> 00:01:22,240 Speaker 1: the first tetrapod strutted its stuff. In other words, much 23 00:01:22,240 --> 00:01:25,120 Speaker 1: of the software was in place well before the walk 24 00:01:25,120 --> 00:01:29,480 Speaker 1: about hardware. The researchers studied the neural circuitry of the 25 00:01:29,560 --> 00:01:33,039 Speaker 1: little skate. This cartilaginous fish might not be much to 26 00:01:33,080 --> 00:01:35,560 Speaker 1: look at, but it's considered one of the most primitive 27 00:01:35,640 --> 00:01:39,440 Speaker 1: vertebrates alive today. Travel back roughly four and twenty million 28 00:01:39,520 --> 00:01:42,200 Speaker 1: years and you'll find a common ancestor of both skates 29 00:01:42,400 --> 00:01:46,160 Speaker 1: and tetrapods. The little skate is also interesting because it's 30 00:01:46,160 --> 00:01:49,800 Speaker 1: one of several ambulatory fish that walk across the sea floor. 31 00:01:50,400 --> 00:01:53,240 Speaker 1: The skate uses its large pectoral fins to swim and 32 00:01:53,520 --> 00:01:57,680 Speaker 1: smaller pelvic fins to walk with alternating left right motions, 33 00:01:57,760 --> 00:02:00,520 Speaker 1: much like the gate of a land animal. This similarity 34 00:02:00,560 --> 00:02:03,920 Speaker 1: impressed the researchers, but these similarities would go beyond movement. 35 00:02:04,600 --> 00:02:07,800 Speaker 1: The team employed RNA sequencing to study the expressed genes 36 00:02:07,840 --> 00:02:11,079 Speaker 1: in these skates motor neurons. Many of these genes pop 37 00:02:11,200 --> 00:02:13,960 Speaker 1: up in mammals as well, and that includes neural subtypes 38 00:02:14,040 --> 00:02:17,720 Speaker 1: involved in the muscle control of bending and straightening limbs. This, 39 00:02:17,840 --> 00:02:21,840 Speaker 1: according to the study findings, constitutes a conserved genetic program 40 00:02:22,000 --> 00:02:26,160 Speaker 1: for walking. Study co author Jeremy S. Dayson says that 41 00:02:26,240 --> 00:02:30,480 Speaker 1: neither swimming nor walking accurately described the skates movements, but 42 00:02:30,639 --> 00:02:33,960 Speaker 1: perhaps this isn't too surprising given the human centric nature 43 00:02:33,960 --> 00:02:37,359 Speaker 1: of our language, he said via email. The skate ray 44 00:02:37,480 --> 00:02:41,960 Speaker 1: mode I would call ambulatory swimming, whereas the axial tail 45 00:02:42,000 --> 00:02:46,120 Speaker 1: based is more like spinal swimming. The ambulatory swimming mode 46 00:02:46,240 --> 00:02:48,760 Speaker 1: is really the one which made walking possible in both 47 00:02:48,800 --> 00:02:52,959 Speaker 1: skates and tetrapods. The study sheds light on the underwater 48 00:02:53,080 --> 00:02:55,320 Speaker 1: history of walking, but the researchers hope that it will 49 00:02:55,400 --> 00:02:58,360 Speaker 1: lead to an improved understanding of motor neurons and even 50 00:02:58,360 --> 00:03:01,840 Speaker 1: the treatment of human neurological to orders. Jason stresses that 51 00:03:01,919 --> 00:03:04,840 Speaker 1: while the neural complexity of higher organisms does hinder our 52 00:03:04,880 --> 00:03:07,880 Speaker 1: study of animals such as mice, the little skates archaic 53 00:03:07,960 --> 00:03:11,640 Speaker 1: simplicity makes it a perfect starting point. He said, I 54 00:03:11,639 --> 00:03:14,080 Speaker 1: think one of the advantages of studying neural circuits and 55 00:03:14,160 --> 00:03:16,840 Speaker 1: skates is that they can accomplish this behavior using a 56 00:03:16,880 --> 00:03:20,360 Speaker 1: relatively simple set of connections between neurons and muscle, we 57 00:03:20,440 --> 00:03:23,040 Speaker 1: hope we can exploit the simplicity to understand the basic 58 00:03:23,120 --> 00:03:27,280 Speaker 1: architecture of the circuits controlling walking. The exact wiring of 59 00:03:27,320 --> 00:03:29,960 Speaker 1: these circuits is still not fully understood in humans or 60 00:03:30,000 --> 00:03:32,880 Speaker 1: other tetrapods, but such knowledge could one day aid in 61 00:03:32,880 --> 00:03:35,440 Speaker 1: the treatment and repair of human spinal cord injuries and 62 00:03:35,560 --> 00:03:39,160 Speaker 1: motor neuron diseases such as a myotrophic lateral sclerosis or 63 00:03:39,280 --> 00:03:41,920 Speaker 1: a l S. But as the saying goes, you have 64 00:03:41,960 --> 00:03:50,520 Speaker 1: to crawl before you can walk, or should we say swim. 65 00:03:50,520 --> 00:03:53,600 Speaker 1: Today's episode was originally produced by Tristan McNeil and is 66 00:03:53,640 --> 00:03:56,240 Speaker 1: based on the article ain't fish strutted the sea floor 67 00:03:56,400 --> 00:03:59,560 Speaker 1: before land Animals? On How stuff Works dot Com, written 68 00:03:59,600 --> 00:04:02,640 Speaker 1: by rob Bert Lamb. To hear more from Robert about 69 00:04:02,640 --> 00:04:05,960 Speaker 1: things strutting to see floor, check out his weird fiction 70 00:04:06,040 --> 00:04:09,280 Speaker 1: podcast mini series The second oil Age. You'll hear a 71 00:04:09,280 --> 00:04:12,480 Speaker 1: familiar voice in the first episode. Brain Stuff is production 72 00:04:12,520 --> 00:04:14,800 Speaker 1: of I Heart Radio in partnership with how Stuffworks dot 73 00:04:14,840 --> 00:04:18,000 Speaker 1: Com and is produced by Tyler clang Or more podcasts 74 00:04:18,040 --> 00:04:21,280 Speaker 1: from my heart Radio, visit the iHeart Radio app, Apple podcasts, 75 00:04:21,320 --> 00:04:23,160 Speaker 1: or wherever you listen to your favorite shows.