Global warming made an ancient type of horse shrink to the size
of a cat, scientists have said.
Sifrhippus is the earliest known horse. It
lived in the forests of North America more than 50 million years
ago. It was small to start off with, about the size of a small
dog.
Over the next 175,000 years the Earth's temperature rose by
about 12C. During this time, Sifrhippus became even smaller until
it was just the size of a cat!
Scientists from the USA looked at fossils of Sifrhippus's teeth
and found that their change in size exactly matched the change in
temperatures. They concluded that the animal had evolved to cope
with the warmer atmosphere.
Fossilised teeth helped
scientists to understand why ancient horses were
smaller
Larger animals conserve more body heat than small ones. So it is
better to be smaller in a warmer climate.
This explains why in two thirds of mammals, ones that live in
hot countries are smaller than their cousins who live in colder
places.
What will happen to animals in the future?
Now scientists are asking: how will animals and plants react to
climate change in the future?
Experts have already started to notice that the size of some
birds may be decreasing.
The ancient horse had 175,000 years to evolve. But global
temperatures are predicted to rise by as much as 4C over the next
100 years. Will our creatures be able to adapt that quickly?