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
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