1 00:00:01,920 --> 00:00:06,960 Speaker 1: Welcome to Brainstuff, a production of iHeart Radio, Hey brain Stuff, 2 00:00:07,000 --> 00:00:12,680 Speaker 1: Lauren Bobo bomb Here. Mammoths, mastodons, and sabretooth cats weren't 3 00:00:12,720 --> 00:00:16,959 Speaker 1: the only giants roaming ancient America. The Palistocene was a 4 00:00:17,000 --> 00:00:20,520 Speaker 1: global epoch that kicked off two point six million years ago. 5 00:00:21,079 --> 00:00:23,880 Speaker 1: It lasted right up until Earth's most recent ice age, 6 00:00:24,000 --> 00:00:28,240 Speaker 1: ended about eleven thousand, seven hundred years before the present day. 7 00:00:29,120 --> 00:00:32,240 Speaker 1: When you live in a cold environment, being big has 8 00:00:32,240 --> 00:00:36,440 Speaker 1: its advantages. Large animals tend to conserve body heat more 9 00:00:36,479 --> 00:00:39,199 Speaker 1: easily than smaller ones, and this is one of the 10 00:00:39,240 --> 00:00:42,839 Speaker 1: major reasons why colossal mammals were so widespread during the 11 00:00:42,880 --> 00:00:48,640 Speaker 1: frigid Pleistocene. Castroides was very much a product of its time. 12 00:00:49,479 --> 00:00:53,760 Speaker 1: The largest rodent in Pleistocene North America, this very big 13 00:00:53,800 --> 00:00:56,800 Speaker 1: beaver grew to more than seven ft long from tail 14 00:00:56,840 --> 00:00:59,520 Speaker 1: to snout that's over two meters, and could have weighed 15 00:00:59,520 --> 00:01:01,440 Speaker 1: as much as two hundred and twenty pounds or a 16 00:01:01,520 --> 00:01:07,040 Speaker 1: hundred kilos or more, rivaling the American black bear in size. 17 00:01:07,440 --> 00:01:12,400 Speaker 1: Casteroids utterly dwarfed the beavers that live today. Modern Eurasian 18 00:01:12,400 --> 00:01:15,400 Speaker 1: and American beaver species clock in it just around three 19 00:01:15,440 --> 00:01:18,160 Speaker 1: ft long, a bit less than a meter, and weigh 20 00:01:18,240 --> 00:01:21,440 Speaker 1: somewhere between twenty nine and seventy seven pounds that's about 21 00:01:21,480 --> 00:01:26,640 Speaker 1: thirteen to thirty five kilos. Proportionately, Casteroids had a narrower 22 00:01:26,680 --> 00:01:30,200 Speaker 1: tail and shorter legs, albeit with bigger hind feet than 23 00:01:30,280 --> 00:01:34,120 Speaker 1: it's extant relatives. We also know that it didn't eat 24 00:01:34,160 --> 00:01:37,920 Speaker 1: the same foods. Woody plants are a crucial part of 25 00:01:38,000 --> 00:01:42,600 Speaker 1: every living beaver's diet. The critters used chisel like incisors 26 00:01:42,640 --> 00:01:45,600 Speaker 1: that's their front teeth to gnaw through bark and take 27 00:01:45,640 --> 00:01:50,240 Speaker 1: down trees. But even though casteroids incisors grew to be 28 00:01:50,240 --> 00:01:54,280 Speaker 1: a whopping six inches or fifteen centimeters long, the teeth 29 00:01:54,360 --> 00:01:58,920 Speaker 1: had duller edges. By comparison, dental differences would have made 30 00:01:58,920 --> 00:02:01,800 Speaker 1: it a lot harder for casteroids to eat tree bark, 31 00:02:02,440 --> 00:02:05,360 Speaker 1: and indeed, it looks like this was not really on 32 00:02:05,400 --> 00:02:10,960 Speaker 1: their menu. Using isotropic signatures in casteroid's teeth from Ohio 33 00:02:11,080 --> 00:02:14,760 Speaker 1: and the yukon En study found that the giant beaver 34 00:02:15,080 --> 00:02:19,239 Speaker 1: mostly ate softer aquatic plants. The findings say a lot 35 00:02:19,280 --> 00:02:22,520 Speaker 1: about the rodents ecological niche and why it might have 36 00:02:22,600 --> 00:02:28,280 Speaker 1: died out For starters casteroids probably didn't build dams, not 37 00:02:28,400 --> 00:02:32,120 Speaker 1: that there's anything unusual about that. The earliest known beavers 38 00:02:32,160 --> 00:02:36,079 Speaker 1: appeared during the Eocene epoch, which lasted between about fifty 39 00:02:36,120 --> 00:02:40,000 Speaker 1: six and thirty four million years ago. New evidence suggests 40 00:02:40,040 --> 00:02:43,600 Speaker 1: that the wood harvesting specialists came along much later, perhaps 41 00:02:43,600 --> 00:02:47,320 Speaker 1: around twenty million years ago. In all likelihood, these bark 42 00:02:47,400 --> 00:02:50,400 Speaker 1: fanciers used wood as a food source before any of 43 00:02:50,400 --> 00:02:56,079 Speaker 1: them started constructing dams. Since casteroids fed on aquatic plants, 44 00:02:56,400 --> 00:03:00,360 Speaker 1: its survival would have depended on wetland habitats. The animal 45 00:03:00,400 --> 00:03:04,520 Speaker 1: was highly successful for a time. Casteroids fossils representing at 46 00:03:04,600 --> 00:03:08,000 Speaker 1: least two distinct species have been documented in the Great Plains, 47 00:03:08,120 --> 00:03:15,520 Speaker 1: the Great Lakes, the American South Alaska, and numerous Canadian provinces. Unfortunately, 48 00:03:15,560 --> 00:03:19,120 Speaker 1: for the mega sized beaver, North America became warmer and 49 00:03:19,320 --> 00:03:23,040 Speaker 1: drier after the Last Ice Age ended, wetlands grew scarcer 50 00:03:23,120 --> 00:03:27,360 Speaker 1: as a result. Today's beavers used their logging skills to 51 00:03:27,480 --> 00:03:29,760 Speaker 1: reshape the land around them so that it meets their 52 00:03:29,760 --> 00:03:33,400 Speaker 1: own needs. With some well placed wood in the nearest stream, 53 00:03:33,440 --> 00:03:38,480 Speaker 1: a determined beaver can engineer brandon new ponds. Yet, if 54 00:03:38,520 --> 00:03:42,160 Speaker 1: casteroids didn't harvest wood or build dams. It couldn't have 55 00:03:42,200 --> 00:03:46,760 Speaker 1: followed suit. So theoretically, the decline in natural wetlands left 56 00:03:46,800 --> 00:03:50,360 Speaker 1: the giant beaver more susceptible to extinction. The last of 57 00:03:50,400 --> 00:03:58,880 Speaker 1: these creatures perished around ten thousand years ago. Today's episode 58 00:03:58,880 --> 00:04:01,360 Speaker 1: was written by Mark man Scene and produced by Tyler Clang. 59 00:04:01,760 --> 00:04:03,880 Speaker 1: For more and listen lots of other big topics, visit 60 00:04:03,920 --> 00:04:06,640 Speaker 1: how stuff works dot com. Brain Stuff is production of 61 00:04:06,680 --> 00:04:09,040 Speaker 1: I Heart Radio. For more podcasts to my heart Radio, 62 00:04:09,200 --> 00:04:11,800 Speaker 1: visit the i heart Radio app, Apple Podcasts, or wherever 63 00:04:11,840 --> 00:04:13,160 Speaker 1: you listen to your favorite shows.