WEBVTT 00:00:00.000 --> 00:00:17.230 align:middle line:90% 00:00:17.230 --> 00:00:21.580 align:middle line:84% The creature’s full scientific name is Carcharocles megalodon. 00:00:21.580 --> 00:00:26.690 align:middle line:84% “Megalodon” means simply, “giant tooth,” derived from Greek. 00:00:26.690 --> 00:00:32.610 align:middle line:84% Fossil evidence of the megalodon occurs most often as giant shark teeth. 00:00:32.610 --> 00:00:35.940 align:middle line:84% Adult megalodon teeth may be as big as one’s palm. 00:00:35.940 --> 00:00:39.510 align:middle line:90% Some are even larger. 00:00:39.510 --> 00:00:45.160 align:middle line:84% Fossils suggest that megalodons lived in tropical and temperate oceans worldwide. 00:00:45.160 --> 00:00:48.160 align:middle line:84% The megalodon is often compared to the great white shark, 00:00:48.160 --> 00:00:54.200 align:middle line:84% but both species have descended along different, albeit closely related lineages. 00:00:54.200 --> 00:00:57.020 align:middle line:84% Sharks are known for their stability through evolution. 00:00:57.020 --> 00:01:02.910 align:middle line:84% And so, scientists believe that a day in a megalodon’s life would resemble that of other 00:01:02.910 --> 00:01:04.260 align:middle line:90% top predator sharks. 00:01:04.260 --> 00:01:18.240 align:middle line:84% Here, the Isthmus of Panama – the land that would connect North America with South America 00:01:18.240 --> 00:01:22.560 align:middle line:90% – has not yet emerged from the ocean. 00:01:22.560 --> 00:01:25.230 align:middle line:90% A female megalodon surveys the area. 00:01:25.230 --> 00:01:26.750 align:middle line:90% She’s pregnant. 00:01:26.750 --> 00:01:28.920 align:middle line:90% She came here to give birth. 00:01:28.920 --> 00:01:34.870 align:middle line:84% While we don’t know for how long, her pregnancy could have taken over a year. 00:01:34.870 --> 00:01:42.850 align:middle line:84% As some other large sharks do today, the mother shark gives birth to live young. 00:01:42.850 --> 00:01:47.020 align:middle line:84% The mother shark is truly giant, about the size of a bus. 00:01:47.020 --> 00:01:53.780 align:middle line:84% And so these infant sharks are similarly big, about 2 meters or more from nose to tail. 00:01:53.780 --> 00:01:59.980 align:middle line:84% The mother may stay near her young, but her actions may not be about mothering. 00:01:59.980 --> 00:02:05.000 align:middle line:84% Instead, she’s more about defending an area she may have used as a feeding ground. 00:02:05.000 --> 00:02:07.540 align:middle line:90% Hammerhead sharks feed here, too. 00:02:07.540 --> 00:02:11.599 align:middle line:84% And so, as she keeps territory for herself, she also 00:02:11.599 --> 00:02:13.390 align:middle line:90% keeps her babies safe from the hammerheads. 00:02:13.390 --> 00:02:16.210 align:middle line:90% 00:02:16.210 --> 00:02:19.560 align:middle line:90% Even at birth, the infant sharks are formidable. 00:02:19.560 --> 00:02:26.390 align:middle line:84% They’ll prey on smaller fish, mollusks, and on small marine mammals if they’re present. 00:02:26.390 --> 00:02:28.780 align:middle line:90% The mother, however, seeks larger prey. 00:02:28.780 --> 00:02:32.780 align:middle line:84% She is easily capable of killing sizeable marine mammals, 00:02:32.780 --> 00:02:36.480 align:middle line:84% like whales, because she is far bigger than they are. 00:02:36.480 --> 00:02:43.550 align:middle line:84% Tooth marks on fossil whale bones indicate deep megalodon bites. 00:02:43.550 --> 00:02:46.790 align:middle line:90% The female bites and then shakes her prey. 00:02:46.790 --> 00:02:50.745 align:middle line:84% The serrated edges of her teeth cut heavy flesh like giant steak knives. 00:02:50.745 --> 00:02:54.010 align:middle line:90% 00:02:54.010 --> 00:02:57.650 align:middle line:84% If megalodons behaved like other large predatory sharks, 00:02:57.650 --> 00:03:01.750 align:middle line:84% her male mate likely remained apart and independent. 00:03:01.750 --> 00:03:05.760 align:middle line:84% While he is still larger than the great white sharks we know today, 00:03:05.760 --> 00:03:08.920 align:middle line:90% he is only about half the female’s size. 00:03:08.920 --> 00:03:14.170 align:middle line:84% Among megalodons, if sheer size was any indication, females rule. 00:03:14.170 --> 00:03:16.900 align:middle line:90% 00:03:16.900 --> 00:03:22.530 align:middle line:84% The cycle of mating, birth, and hunting continued in these shallow seas until about 2.6 00:03:22.530 --> 00:03:23.940 align:middle line:90% million years ago. 00:03:23.940 --> 00:03:27.910 align:middle line:84% In the time of the megalodons, continents drifted together. 00:03:27.910 --> 00:03:31.670 align:middle line:90% Sea currents and sea levels changed. 00:03:31.670 --> 00:03:35.480 align:middle line:84% The abundance of prey rose and fell throughout megalodon’s reign. 00:03:35.480 --> 00:03:41.950 align:middle line:84% But as the Pliocene epoch went on, sharks became more competitive, possibly even quicker 00:03:41.950 --> 00:03:43.400 align:middle line:90% and more agile. 00:03:43.400 --> 00:03:47.680 align:middle line:84% These factors, and perhaps others, spelled the end of the megalodon. 00:03:47.680 --> 00:03:51.800 align:middle line:90% 00:03:51.800 --> 00:03:56.130 align:middle line:84% Why is there so little material evidence of megalodons today? 00:03:56.130 --> 00:04:00.300 align:middle line:84% Well, they were sharks, and all sharks are cartilaginous fish. 00:04:00.300 --> 00:04:06.230 align:middle line:84% Megalodon skeletons had few hard bones, and were mostly cartilage. 00:04:06.230 --> 00:04:09.090 align:middle line:90% A dinosaur leaves bones when it dies. 00:04:09.090 --> 00:04:14.900 align:middle line:84% Bones enable one to estimate a body’s size, structure and function. 00:04:14.900 --> 00:04:18.500 align:middle line:84% But since sharks’ skeletons are almost totally cartilage, 00:04:18.500 --> 00:04:26.390 align:middle line:84% and cartilage decomposes easily after death, almost nothing of a megalodon is left behind. 00:04:26.390 --> 00:04:28.820 align:middle line:90% Shark teeth, however, fossilize easily. 00:04:28.820 --> 00:04:35.110 align:middle line:84% So scientists use fossil megalodon teeth to estimate other details about the animals. 00:04:35.110 --> 00:04:39.360 align:middle line:84% The enormous size of megalodon teeth, compared to teeth of living sharks, 00:04:39.360 --> 00:04:43.595 align:middle line:84% is a significant reason why scientists think the megalodon was so large. 00:04:43.595 --> 00:04:47.260 align:middle line:90% 00:04:47.260 --> 00:04:51.970 align:middle line:84% But fossil teeth paint an incomplete picture of this magnificent animal, 00:04:51.970 --> 00:04:55.825 align:middle line:84% and the scarcity of other hard evidence continues to challenge scientists. 00:04:55.825 --> 00:04:58.390 align:middle line:90% 00:04:58.390 --> 00:05:03.240 align:middle line:84% For now, some ideas about the megalodon are based on assumptions of how it could have 00:05:03.240 --> 00:05:09.300 align:middle line:84% resembled today’s sharks in form, ecology, and behavior. 00:05:09.300 --> 00:05:34.080 align:middle line:90%