14
Science and technology
The Week Junior • 11 June 2022
S
cientists have solved one of the oldest mysteries
about dinosaurs: whether they had cold or warm
blood. The temperature of an animal’s blood is
linked to its metabolism – the rate at which its body
extracts energy from food. Metabolism affects how
much an animal needs to eat, how active it can be
and even where it can survive, so understanding
their metabolisms is a huge breakthrough in learning
about how these extinct beasts lived.
Warm-blooded animals like mammals and birds
have fast metabolisms; they need to eat frequently
but can be active even in cold climates. Cold-blooded
animals such as reptiles have slower
metabolisms and can eat less often
but their activity depends on the
temperatures around them and
they get sluggish when they
cool down too much.
Some experts have
argued that since dinosaurs
were reptiles, they must
have been cold-blooded.
Others suggest that because
warm-blooded birds are
descended from dinosaurs,
at least some dinos might have been
warm-blooded too.Jasmina Wiemann, from California Institute of
Technology in the US, found an ingenious way to
solve the puzzle, by measuring the chemical make-up
of fossils (the remains of ancient life transformed
into rocky minerals after being buried for millions
of years). She realised some of the chemicals that
transport energy in an animal’s body can survive
fossilisation, so the amount of these present in a
dinosaur fossil can reveal the rate of its metabolism.
Working with an international team, Wiemann
used her method to study 55 different species. Their
surprising results suggest that the very first dinosaurs
already had warm-blooded metabolisms
when they evolved 240 million years
ago. So did the
majority of their
descendants,
from predators like
T. rex to plant-eating
giants like Diplodocus.
However, some plant-eaters- such as the duck-billed
hadrosaurs and the horned
Triceratops – later developed
slower metabolisms and colder
blood. The armoured Stegosaurus
had the slowest metabolism of all.
Most dinos had warm blood
When early fossil hunters realised that
dinosaurs were a distinct group of ancient
animals in the early 19th century, they
assumed that because dinos were giant
reptiles, they would have reptile-like shapes
and lifestyles despite their enormous size.
Many early images of dinosaurs showed them
as lumbering, sluggish lizards, like the ones
still on display at Crystal Palace in London. As
later fossil finds revealed that many dinosaurs
had much more agile and varied shapes,
scientists began to consider whether they
could also have had more active lifestyles.Changing views of dinosaurs
Active hunters like Velociraptor
were warm-blooded.Dinosaur statues
at Crystal Palace.ANCI
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1824.The cold-blooded
giant Stegosaurus.