1
00:00:02,040 --> 00:00:07,040
Speaker 1: Welcome to brain stuff. From how stuff works, Hey, brain stuff,

2
00:00:07,120 --> 00:00:09,760
Speaker 1: Lauren boge obamb here. Many of us have seen a

3
00:00:09,800 --> 00:00:13,000
Speaker 1: turtle tucking itself into its protective shell, pulling in not

4
00:00:13,080 --> 00:00:15,440
Speaker 1: only its four legs, but its head and tail as well.

5
00:00:16,040 --> 00:00:19,400
Speaker 1: But while its shell shields a turtle's tender innards, it

6
00:00:19,480 --> 00:00:22,840
Speaker 1: wasn't originally designed for that purpose, as an international group

7
00:00:22,840 --> 00:00:26,160
Speaker 1: of scientists has found. Instead, they say the turtle shell

8
00:00:26,280 --> 00:00:30,280
Speaker 1: most likely began as a digging tool. Tyler Lison, who

9
00:00:30,400 --> 00:00:32,720
Speaker 1: is the lead author of the studying question and a

10
00:00:32,760 --> 00:00:36,200
Speaker 1: paleontologist at the Denver Museum of Nature and Science, writes

11
00:00:36,280 --> 00:00:40,800
Speaker 1: that when turtles first began developing shells a major evolutionary transition.

12
00:00:41,120 --> 00:00:44,920
Speaker 1: The process included a broadening of the ribs. Broadened ribs

13
00:00:44,920 --> 00:00:48,559
Speaker 1: made the turtles thoraxic region, or chest, more rigid. But

14
00:00:48,680 --> 00:00:51,360
Speaker 1: the puzzling thing is that a rigid chest means it's

15
00:00:51,400 --> 00:00:54,600
Speaker 1: harder for the animal to breathe easily or move swiftly,

16
00:00:55,080 --> 00:00:59,520
Speaker 1: hardly changes that appear to enhance protective capabilities. But that's

17
00:00:59,560 --> 00:01:02,960
Speaker 1: because initially, turtle shells made of more than fifty fused

18
00:01:03,000 --> 00:01:06,440
Speaker 1: bones and their broad ribs were developed not for protection

19
00:01:06,680 --> 00:01:08,800
Speaker 1: but to lend stability to the turtles so it could

20
00:01:08,840 --> 00:01:12,640
Speaker 1: forcefully dig with its forelimbs. The researchers found being able

21
00:01:12,680 --> 00:01:14,840
Speaker 1: to dig into the ground for food and shelter, they

22
00:01:14,880 --> 00:01:18,199
Speaker 1: theorize allowed the turtles to move from the land into

23
00:01:18,280 --> 00:01:21,039
Speaker 1: the water. This may have saved them in their early

24
00:01:21,080 --> 00:01:26,080
Speaker 1: evolutionary history, specifically during the Permian Triassic extinction, the greatest

25
00:01:26,080 --> 00:01:29,160
Speaker 1: mass extinction ever and one which was spurred by hot,

26
00:01:29,319 --> 00:01:33,000
Speaker 1: dry weather. These insights came after two of the studies

27
00:01:33,040 --> 00:01:35,959
Speaker 1: co authors discovered several specimens of a two hundred and

28
00:01:36,000 --> 00:01:40,400
Speaker 1: sixty million year old turtle named Untosaurus africanus, the oldest

29
00:01:40,440 --> 00:01:44,240
Speaker 1: to known partially shelled proto turtle. These specimens, along with

30
00:01:44,319 --> 00:01:46,959
Speaker 1: another partially shelled turtle found by a young boy in

31
00:01:47,000 --> 00:01:51,240
Speaker 1: South Africa, indicate turtles developed shells for use as digging aids.

32
00:01:51,960 --> 00:01:55,880
Speaker 1: The scientists found similarities between these turtles and gopher tortoises,

33
00:01:56,080 --> 00:01:58,840
Speaker 1: which use their heads and next to brace themselves while

34
00:01:58,840 --> 00:02:01,680
Speaker 1: they dig with their forelimbs. The authors believe that the

35
00:02:01,760 --> 00:02:04,960
Speaker 1: turtle's shell as a protective enclosure is an x adaption,

36
00:02:05,400 --> 00:02:09,000
Speaker 1: meaning an evolutionary trait that originally served one function, but

37
00:02:09,280 --> 00:02:13,080
Speaker 1: winds up serving another. Scientists have been arguing for at

38
00:02:13,120 --> 00:02:15,960
Speaker 1: least two hundred years over whether the turtle's shell evolved

39
00:02:16,000 --> 00:02:19,600
Speaker 1: from bony scales like those on an armadillo or certain lizards,

40
00:02:19,919 --> 00:02:23,200
Speaker 1: or as part of its ribs broadening. Thanks to recent

41
00:02:23,240 --> 00:02:26,680
Speaker 1: discovery of partially shelled stem turtles, it now seems that

42
00:02:26,720 --> 00:02:34,919
Speaker 1: the latter theory is more likely. Today's episode was written

43
00:02:34,919 --> 00:02:38,000
Speaker 1: by Melanie red Zeki McManus and produced by Tyler Clang.

44
00:02:38,320 --> 00:02:42,040
Speaker 1: For more on this and lots of other evolutionarily advantageous topics,

45
00:02:42,160 --> 00:02:56,000
Speaker 1: visit our home planet, how Stuff Works dot com