WEBVTT - Can We Tell Whether a Dinosaur Was Male or Female? 0:00:01.920 --> 0:00:06.360 Welcome to brain Stuff, a production of iHeart Radio, Hey 0:00:06.480 --> 0:00:10.600 brain Stuff Lauren Bogle bomb here. Sue is the largest, 0:00:10.720 --> 0:00:14.920 most complete Tyrannosaurus Rex skeleton in the world. Sue is 0:00:14.960 --> 0:00:18.160 an impressive specimen, standing more than thirteen feet that's four 0:00:18.200 --> 0:00:21.520 meters tall and forty two ft or thirteen meters long. 0:00:22.200 --> 0:00:25.680 Many dinosaur fossils have missing or broken bones, but Sue 0:00:25.800 --> 0:00:29.760 is more than complete, so it was also often displayed 0:00:29.800 --> 0:00:32.800 as a real skeleton, not a cast. The bones that 0:00:32.840 --> 0:00:35.680 you can see are the real sixty seven million year 0:00:35.720 --> 0:00:41.280 old deal. Paleontologist Sue Hendrickson discovered the dinosaur's bones in 0:00:41.320 --> 0:00:45.840 South Dakota on August twelfth of nine. Since then, researchers 0:00:45.840 --> 0:00:49.200 have figured out a lot about Sue's life. In spite 0:00:49.240 --> 0:00:52.080 of breaking some ribs, Sue lived to a relatively old 0:00:52.080 --> 0:00:54.560 age for a dinosaur, at least according to signs of 0:00:54.560 --> 0:00:57.920 wear on the bones. A Researchers also estimate that the 0:00:57.960 --> 0:01:01.080 dinosaur weighed about seven tons, which is around as much 0:01:01.120 --> 0:01:04.880 as a male African elephant. But what scientists don't know 0:01:05.080 --> 0:01:09.600 is whether Sue was male or female. With just about 0:01:09.640 --> 0:01:13.440 all living animals that use sexual reproduction, it's pretty easy 0:01:13.520 --> 0:01:16.200 to figure out which sex is which, all you have 0:01:16.280 --> 0:01:18.520 to do is observe their behavior or take a look 0:01:18.560 --> 0:01:21.280 at their sex organs. Figuring out the sex of a 0:01:21.319 --> 0:01:25.039 dinosaur is a little trickier though there aren't any around today, 0:01:25.120 --> 0:01:28.559 so you can't observe their behavior, and since sex organs 0:01:28.560 --> 0:01:31.920 are made of soft tissue, they don't fossilize well. On 0:01:32.000 --> 0:01:36.080 top of that, most paleontologists believe that dinosaurs, like birds, 0:01:36.480 --> 0:01:39.960 used one opening called a cloaca for both reproduction and 0:01:40.040 --> 0:01:44.319 expulsion of liquid and solid waste, so even if researchers 0:01:44.360 --> 0:01:47.720 find a dinosaur fossil with well preserved skin, they still 0:01:47.760 --> 0:01:52.840 may not know it's sex for sure. DNA master reference 0:01:52.880 --> 0:01:56.160 for figuring out what's what isn't much help with dinosaurs either. 0:01:56.680 --> 0:01:59.559 While you can usually tell male and female mammals apart 0:01:59.640 --> 0:02:03.560 by their X and Y chromosomes, reptiles don't follow those rules. 0:02:04.000 --> 0:02:07.400 In many reptilian species, the temperature of the egg, not 0:02:07.720 --> 0:02:12.359 the chromosomes inside it, determines the sex. Plus DNA breaks 0:02:12.400 --> 0:02:17.800 down during fossilization, leaving little for researchers to analyze. But 0:02:18.080 --> 0:02:20.560 that doesn't mean figuring out the sex of a dinosaur 0:02:20.560 --> 0:02:24.680 fossil is impossible. Every once in an extremely long while, 0:02:24.880 --> 0:02:28.200 researchers might find a skeleton with eggs inside it a 0:02:28.280 --> 0:02:31.680 pretty good clue that one was female. One such find 0:02:31.720 --> 0:02:35.200 cropped up in China in two thousand five, but eggs 0:02:35.240 --> 0:02:38.720 aren't always the best indicator. It might seem likely that 0:02:38.760 --> 0:02:41.360 a skeleton perched to top a nest of eggs belonged 0:02:41.400 --> 0:02:44.040 to a female, but it's just as likely that male 0:02:44.080 --> 0:02:47.720 dinosaurs like male EMUs and ostriches were the ones that 0:02:47.840 --> 0:02:52.359 did the brooding. Another potential way of dividing males from 0:02:52.400 --> 0:02:56.440 females is through studying sexual dimorphism. To think of male 0:02:56.480 --> 0:03:00.560 peacocks that display huge ornate tails to attempt to impress 0:03:00.680 --> 0:03:05.320 relatively nondescript female p hens. It could be that differences 0:03:05.360 --> 0:03:07.639 in neck frills and head crests had to do with 0:03:07.720 --> 0:03:10.760 the dinosaurs need to attract a mate. The size and 0:03:10.760 --> 0:03:13.600 proportion of a dinosaur's body may have been sex related 0:03:13.639 --> 0:03:18.800 to Paleobiologist Phil Center hypothesizes that the ultralong necks of 0:03:18.840 --> 0:03:22.720 animals like a patosaurus may have evolved through sexual selection, 0:03:23.000 --> 0:03:27.600 with longer necked dinosaurs attracting more or better mates. The 0:03:27.639 --> 0:03:30.040 only trouble with this theory is that even if there 0:03:30.080 --> 0:03:33.440 are sex differences in dinosaurs, we still don't know which 0:03:33.480 --> 0:03:37.440 sexes which. Did a female triceratops use its neck frill 0:03:37.480 --> 0:03:40.040 to attract a mate or was it the other way around, 0:03:40.400 --> 0:03:43.880 where horns and tail spikes for defense against predators or 0:03:43.920 --> 0:03:47.880 for combat with rival males. Without preserved samples of sex 0:03:47.960 --> 0:03:51.360 organs or a time traveling look at dinosaur behavior, it's 0:03:51.400 --> 0:03:56.560 impossible to say. Aside from the serendipitous find of a 0:03:56.600 --> 0:04:00.080 dinosaur fossil filled with eggs or researchers have found and 0:04:00.200 --> 0:04:02.600 one way to figure out if a dinosaur is female, 0:04:02.880 --> 0:04:04.720 at least if she was pregnant at the time of 0:04:04.760 --> 0:04:08.600 her death. In two thousand five, in the journal Science, 0:04:08.840 --> 0:04:11.720 a team of researchers reported the discovery of what's called 0:04:11.840 --> 0:04:16.359 medillary or medillary bone and a Tyrannosaurs rex fossil. In 0:04:16.520 --> 0:04:20.520 birds which have hollow bones, medillary bone lines the interior 0:04:20.600 --> 0:04:24.480 cavity of females bones. Birds use this type of bone 0:04:24.520 --> 0:04:28.080 as a reservoir for the calcium they need to produce eggshells. 0:04:28.760 --> 0:04:31.600 In all likelihood, the t rex whose bones the team 0:04:31.640 --> 0:04:36.680 was studying was both female and pregnant. Unfortunately, Researchers can 0:04:36.720 --> 0:04:39.440 only determine the sex of dinosaurs this way by breaking 0:04:39.480 --> 0:04:42.520 into the interior of the bone. On top of that, 0:04:42.680 --> 0:04:45.400 it only works that the dinosaur was pregnant when she died. 0:04:46.800 --> 0:04:50.880 With groundbreaking discoveries like this and well preserved fossils still 0:04:50.880 --> 0:04:53.880 being unearthed, it may one day be possible to make 0:04:53.920 --> 0:04:57.240 a pretty good guess about a dinosaurs sex, but for 0:04:57.360 --> 0:05:04.920 right now, it's a shot in the darkness m Today's 0:05:04.920 --> 0:05:07.360 episode was written by Tracy V. Wilson and produced by 0:05:07.360 --> 0:05:09.720 Tyler Clang. For more on this and lots of other 0:05:09.800 --> 0:05:13.120 curious topics, visit how stuff works dot com. Brain Stuff 0:05:13.120 --> 0:05:15.520 is production of I Heart Radio. Or more podcasts. To 0:05:15.560 --> 0:05:18.560 my heart Radio, visit the I heart Radio app, Apple Podcasts, 0:05:18.600 --> 0:05:20.400 or wherever you listen to your favorite shows.