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

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