1 00:00:01,920 --> 00:00:06,360 Speaker 1: Welcome to brain Stuff, a production of iHeart Radio, Hey 2 00:00:06,480 --> 00:00:10,600 Speaker 1: brain Stuff Lauren Bogle bomb here. Sue is the largest, 3 00:00:10,720 --> 00:00:14,920 Speaker 1: most complete Tyrannosaurus Rex skeleton in the world. Sue is 4 00:00:14,960 --> 00:00:18,160 Speaker 1: an impressive specimen, standing more than thirteen feet that's four 5 00:00:18,200 --> 00:00:21,520 Speaker 1: meters tall and forty two ft or thirteen meters long. 6 00:00:22,200 --> 00:00:25,680 Speaker 1: Many dinosaur fossils have missing or broken bones, but Sue 7 00:00:25,800 --> 00:00:29,760 Speaker 1: is more than complete, so it was also often displayed 8 00:00:29,800 --> 00:00:32,800 Speaker 1: as a real skeleton, not a cast. The bones that 9 00:00:32,840 --> 00:00:35,680 Speaker 1: you can see are the real sixty seven million year 10 00:00:35,720 --> 00:00:41,280 Speaker 1: old deal. Paleontologist Sue Hendrickson discovered the dinosaur's bones in 11 00:00:41,320 --> 00:00:45,840 Speaker 1: South Dakota on August twelfth of nine. Since then, researchers 12 00:00:45,840 --> 00:00:49,200 Speaker 1: have figured out a lot about Sue's life. In spite 13 00:00:49,240 --> 00:00:52,080 Speaker 1: of breaking some ribs, Sue lived to a relatively old 14 00:00:52,080 --> 00:00:54,560 Speaker 1: age for a dinosaur, at least according to signs of 15 00:00:54,560 --> 00:00:57,920 Speaker 1: wear on the bones. A Researchers also estimate that the 16 00:00:57,960 --> 00:01:01,080 Speaker 1: dinosaur weighed about seven tons, which is around as much 17 00:01:01,120 --> 00:01:04,880 Speaker 1: as a male African elephant. But what scientists don't know 18 00:01:05,080 --> 00:01:09,600 Speaker 1: is whether Sue was male or female. With just about 19 00:01:09,640 --> 00:01:13,440 Speaker 1: all living animals that use sexual reproduction, it's pretty easy 20 00:01:13,520 --> 00:01:16,200 Speaker 1: to figure out which sex is which, all you have 21 00:01:16,280 --> 00:01:18,520 Speaker 1: to do is observe their behavior or take a look 22 00:01:18,560 --> 00:01:21,280 Speaker 1: at their sex organs. Figuring out the sex of a 23 00:01:21,319 --> 00:01:25,039 Speaker 1: dinosaur is a little trickier though there aren't any around today, 24 00:01:25,120 --> 00:01:28,559 Speaker 1: so you can't observe their behavior, and since sex organs 25 00:01:28,560 --> 00:01:31,920 Speaker 1: are made of soft tissue, they don't fossilize well. On 26 00:01:32,000 --> 00:01:36,080 Speaker 1: top of that, most paleontologists believe that dinosaurs, like birds, 27 00:01:36,480 --> 00:01:39,960 Speaker 1: used one opening called a cloaca for both reproduction and 28 00:01:40,040 --> 00:01:44,319 Speaker 1: expulsion of liquid and solid waste, so even if researchers 29 00:01:44,360 --> 00:01:47,720 Speaker 1: find a dinosaur fossil with well preserved skin, they still 30 00:01:47,760 --> 00:01:52,840 Speaker 1: may not know it's sex for sure. DNA master reference 31 00:01:52,880 --> 00:01:56,160 Speaker 1: for figuring out what's what isn't much help with dinosaurs either. 32 00:01:56,680 --> 00:01:59,559 Speaker 1: While you can usually tell male and female mammals apart 33 00:01:59,640 --> 00:02:03,560 Speaker 1: by their X and Y chromosomes, reptiles don't follow those rules. 34 00:02:04,000 --> 00:02:07,400 Speaker 1: In many reptilian species, the temperature of the egg, not 35 00:02:07,720 --> 00:02:12,359 Speaker 1: the chromosomes inside it, determines the sex. Plus DNA breaks 36 00:02:12,400 --> 00:02:17,800 Speaker 1: down during fossilization, leaving little for researchers to analyze. But 37 00:02:18,080 --> 00:02:20,560 Speaker 1: that doesn't mean figuring out the sex of a dinosaur 38 00:02:20,560 --> 00:02:24,680 Speaker 1: fossil is impossible. Every once in an extremely long while, 39 00:02:24,880 --> 00:02:28,200 Speaker 1: researchers might find a skeleton with eggs inside it a 40 00:02:28,280 --> 00:02:31,680 Speaker 1: pretty good clue that one was female. One such find 41 00:02:31,720 --> 00:02:35,200 Speaker 1: cropped up in China in two thousand five, but eggs 42 00:02:35,240 --> 00:02:38,720 Speaker 1: aren't always the best indicator. It might seem likely that 43 00:02:38,760 --> 00:02:41,360 Speaker 1: a skeleton perched to top a nest of eggs belonged 44 00:02:41,400 --> 00:02:44,040 Speaker 1: to a female, but it's just as likely that male 45 00:02:44,080 --> 00:02:47,720 Speaker 1: dinosaurs like male EMUs and ostriches were the ones that 46 00:02:47,840 --> 00:02:52,359 Speaker 1: did the brooding. Another potential way of dividing males from 47 00:02:52,400 --> 00:02:56,440 Speaker 1: females is through studying sexual dimorphism. To think of male 48 00:02:56,480 --> 00:03:00,560 Speaker 1: peacocks that display huge ornate tails to attempt to impress 49 00:03:00,680 --> 00:03:05,320 Speaker 1: relatively nondescript female p hens. It could be that differences 50 00:03:05,360 --> 00:03:07,639 Speaker 1: in neck frills and head crests had to do with 51 00:03:07,720 --> 00:03:10,760 Speaker 1: the dinosaurs need to attract a mate. The size and 52 00:03:10,760 --> 00:03:13,600 Speaker 1: proportion of a dinosaur's body may have been sex related 53 00:03:13,639 --> 00:03:18,800 Speaker 1: to Paleobiologist Phil Center hypothesizes that the ultralong necks of 54 00:03:18,840 --> 00:03:22,720 Speaker 1: animals like a patosaurus may have evolved through sexual selection, 55 00:03:23,000 --> 00:03:27,600 Speaker 1: with longer necked dinosaurs attracting more or better mates. The 56 00:03:27,639 --> 00:03:30,040 Speaker 1: only trouble with this theory is that even if there 57 00:03:30,080 --> 00:03:33,440 Speaker 1: are sex differences in dinosaurs, we still don't know which 58 00:03:33,480 --> 00:03:37,440 Speaker 1: sexes which. Did a female triceratops use its neck frill 59 00:03:37,480 --> 00:03:40,040 Speaker 1: to attract a mate or was it the other way around, 60 00:03:40,400 --> 00:03:43,880 Speaker 1: where horns and tail spikes for defense against predators or 61 00:03:43,920 --> 00:03:47,880 Speaker 1: for combat with rival males. Without preserved samples of sex 62 00:03:47,960 --> 00:03:51,360 Speaker 1: organs or a time traveling look at dinosaur behavior, it's 63 00:03:51,400 --> 00:03:56,560 Speaker 1: impossible to say. Aside from the serendipitous find of a 64 00:03:56,600 --> 00:04:00,080 Speaker 1: dinosaur fossil filled with eggs or researchers have found and 65 00:04:00,200 --> 00:04:02,600 Speaker 1: one way to figure out if a dinosaur is female, 66 00:04:02,880 --> 00:04:04,720 Speaker 1: at least if she was pregnant at the time of 67 00:04:04,760 --> 00:04:08,600 Speaker 1: her death. In two thousand five, in the journal Science, 68 00:04:08,840 --> 00:04:11,720 Speaker 1: a team of researchers reported the discovery of what's called 69 00:04:11,840 --> 00:04:16,359 Speaker 1: medillary or medillary bone and a Tyrannosaurs rex fossil. In 70 00:04:16,520 --> 00:04:20,520 Speaker 1: birds which have hollow bones, medillary bone lines the interior 71 00:04:20,600 --> 00:04:24,480 Speaker 1: cavity of females bones. Birds use this type of bone 72 00:04:24,520 --> 00:04:28,080 Speaker 1: as a reservoir for the calcium they need to produce eggshells. 73 00:04:28,760 --> 00:04:31,600 Speaker 1: In all likelihood, the t rex whose bones the team 74 00:04:31,640 --> 00:04:36,680 Speaker 1: was studying was both female and pregnant. Unfortunately, Researchers can 75 00:04:36,720 --> 00:04:39,440 Speaker 1: only determine the sex of dinosaurs this way by breaking 76 00:04:39,480 --> 00:04:42,520 Speaker 1: into the interior of the bone. On top of that, 77 00:04:42,680 --> 00:04:45,400 Speaker 1: it only works that the dinosaur was pregnant when she died. 78 00:04:46,800 --> 00:04:50,880 Speaker 1: With groundbreaking discoveries like this and well preserved fossils still 79 00:04:50,880 --> 00:04:53,880 Speaker 1: being unearthed, it may one day be possible to make 80 00:04:53,920 --> 00:04:57,240 Speaker 1: a pretty good guess about a dinosaurs sex, but for 81 00:04:57,360 --> 00:05:04,920 Speaker 1: right now, it's a shot in the darkness m Today's 82 00:05:04,920 --> 00:05:07,360 Speaker 1: episode was written by Tracy V. Wilson and produced by 83 00:05:07,360 --> 00:05:09,720 Speaker 1: Tyler Clang. For more on this and lots of other 84 00:05:09,800 --> 00:05:13,120 Speaker 1: curious topics, visit how stuff works dot com. Brain Stuff 85 00:05:13,120 --> 00:05:15,520 Speaker 1: is production of I Heart Radio. Or more podcasts. To 86 00:05:15,560 --> 00:05:18,560 Speaker 1: my heart Radio, visit the I heart Radio app, Apple Podcasts, 87 00:05:18,600 --> 00:05:20,400 Speaker 1: or wherever you listen to your favorite shows.