Ancient cat-sized horse
Earliest known horse shrank because of warmer
climate
Global warming made an ancient type of horse shrink to the size
of a cat, scientists have said.
The earliest known horse, known as Sifrhippus, first appeared in
the forests of North America more than 50 million years ago. It was
small to start off with - it only weighed about five-and-a-half
kilograms! That is about the size of a small dog, like a
terrier.
Over the next 175,000 years Sifrhippus became even smaller until
it was just the size of a cat - weighing in at just under four
kilograms!
During that time, the temperature of the atmosphere had risen by
around 12C.
About one third of all mammal species shrank during the same
period, some by as much as half.
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.
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.
Now the question scientists are asking is: 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?
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Ancient cat-sized horse
Evolution's Missing Chapter on display in
Edinburgh
You can learn a lot from fossils.
By examining ancient fossilised teeth, scientists have been able
to work out what caused the earliest-known horse to shrink to the
size of a cat.
And now fossils found in Scotland that changed scientists'
understanding of evolution on Earth have gone on display in the
National Museum of Scotland in Edinburgh.
Visitors will be able to see the Evolution's Missing Chapter
exhibition until the end of April. It features fossils found in the
Scottish Borders.
The fossils are of plants and animals that lived around 350
million years ago. They were discovered by a palaeontologist, or
prehistoric life expert, Stan Wood.
Before they were found, this period was referred to as a gap in
the fossil record: there had been very little evidence of life on
land between 360 and 345 million years ago.
Some experts believed that there were low levels of oxygen
during the "gap" years, which limited evolution on land. But the
unveiled fossils show that a wide variety of amphibians, plants,
fish and invertebrates existed during this 15 million year
period.
Scientist and broadcaster Sir David Attenborough said the finds
were "wonderful and exciting".
Researchers around the world are excited at the new information
the fossils will provide about the earliest development of life on
land as we know it today.
Nick Fraser, Keeper of Natural Sciences at National Museums
Scotland, said:
"This is a real 'eureka' moment in palaeontology. These fossils
aren't much to look at in and of themselves, but they may prove to
be profoundly important in advancing our understanding of the
earliest development of land-dwelling life as we know it today. For
that reason, we are tremendously excited to be able to give people
the chance to see these fascinating objects first hand."
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