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  • sometimes in science the answer just isn't where you thought it was gonna be

  • and last week in the journal Science advances an international group of

  • researchers published insight into an age-old problem from a pretty surprising

  • place they analyzed dinosaur eggs to get an idea of the mother dinosaurs body

  • temperature when the egg was formed and the results are giving us a much clearer

  • picture of how dinosaurs evolved from cold blooded reptiles to warm-blooded

  • Birds warm-blooded Mis aka endothermy is a huge part of how birds and mammals

  • have been able to spread all across the world it seems to have evolved

  • separately in each group but the result is the same instead of relying on the

  • sun's warmth to maintain our body temperatures we have the freedom to live

  • in a whole range of climates and keep up fairly consistent energy levels at the

  • same time many researchers are pretty sure that birds warm-bloodedness evolved

  • in their dinosaur ancestors but for a long time they've been trying to figure

  • out exactly how and when that happened these days a lot of researchers argue

  • that many dinosaurs were mesothermal isse um we're in between warm and cold

  • blooded like endotherms mezzo thurman

  • now we endotherms maintain our body temperatures at a set point about 37

  • degrees in humans but living mezzo therms don't have a thermostat they just

  • kind of turn on the heat and hope for the best to learn more about how

  • temperature regulation might have evolved in dinosaurs it's important to

  • know what their internal temperatures were if they were warmer than the

  • weather outside that points to at least some control over their body

  • temperatures previous research on this has involved looking at different

  • dinosaurs growth rates which you can calculate based on marks left in their

  • bones kind of like tree rings cold blooded reptiles with their slow

  • metabolism tend to grow slowly while warm-blooded animals tend to have much

  • higher energy levels and therefore it grow more quickly the problem is the

  • relationship between growth rate and metabolism isn't always that simple

  • which means looking at how dinosaurs grew might not be the most reliable way

  • to figure out if they had control over their body temperatures so the authors

  • of this new paper used a different technique one that's only come into use

  • relatively recently it's called clumped isotope paleo thermometry the paleo

  • thermometry part just means measuring temperature in animals usually extinct

  • ones it's the clumped isotope part of the

  • name that really describes what the technique is isotopes are basically

  • versions of the same element with different weights some are more common

  • than others and their abundances can vary based on a variety of factors so

  • when the rarer isotopes clump together within groups of molecules that can tell

  • you a lot about how they got together and what the conditions were like when

  • those molecules formed like what the temperature was in the past some

  • researchers have used the clumped isotope technique on dinosaur egg shells

  • which allowed them to calculate the temperature inside the dinosaur when the

  • egg was formed but as the authors of this paper pointed out the problem is

  • that they've only done that for dinosaurs that lived in warm climates

  • which means it wouldn't matter if they were endothermic or mesothermal

  • or whatever because their temperature would have been close to that of their

  • warm surroundings no matter what when dinosaurs ruled the world from about 230

  • million years ago to around 65 million years ago earth was much warmer than it

  • is today there were still some places with average temperatures below 30

  • degrees or so and some dinosaurs were adapted to live in those lower

  • temperatures so the team applied the clumped isotope technique to eggshells

  • of dinosaurs that lived in places with cooler climates mainly ancient Canada

  • they looked at three different species and in two of them the temperature

  • inside the dinosaurs when these eggs formed was much warmer than the

  • temperature outside would have been in fact at 36 degrees and 44 degrees both

  • temperatures were in line with what we see in endotherms today so these

  • dinosaurs probably had some control over their body temperature although it's

  • hard to tell from this data whether they were Meza therms or endotherms

  • in the other species called Troodon formosus they actually found a range of

  • body temperatures from about 27 to 38 degrees Celsius that could be a sign

  • that they were able to raise their body temperature but not necessarily control

  • it which would indicate that at the very least they weren't cold blooded and may

  • have been mezzo therms so just from looking at the chemistry of eggshells we

  • now understand a lot more about how certain dinosaurs might have controlled

  • their body temperature and if future studies apply the technique to more

  • species we could get a lot closer to understanding how endothermy evolved

  • over time which just goes to show what we can learn from looking in some pretty

  • unexpected places thanks for watching this episode of size

  • which was brought to you with the help of our amazing patrons if you want to

  • get involved and help us continue making videos about everything from dinosaur

  • eggs to supernovas check out patreon.com/scishow

sometimes in science the answer just isn't where you thought it was gonna be

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B1 中級

恐竜はおそらく冷血ではなかった、卵の殻によると (Dinosaurs Probably Weren't Cold-Blooded, According to Eggshells)

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    林宜悉 に公開 2021 年 01 月 14 日
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