March 8, 2017 by John Long, The
Conversation
About 375 million years ago,
certain fishes had developed powerfully strong paired fins that were capable of
transporting them out of the water and onto land.
These fishes would eventually
evolve into the first truly terrestrial animals, called tetrapods.
They had four limbs bearing digits – fingers and toes – to help them when they
walked around around on land.
But one of the biggest mysteries
for scientists is figuring out what could have driven such fishes out of the
water and onto land in the first place.
Was it availability of new food
sources, or perhaps their need to escape from predators in the water?
A new theory says it was improved
vision, as shown by dramatic increases in eye size and visual acuity, that
enabled fishes peeping upwards at the waterline to spot prey on land.
This would have motivated them to
venture out of the water to hunt for food. The new research is published today by Malcolm MacIver
from Northwestern University in the US and colleagues. They have named this the
"Buena Vista" hypothesis, from the Spanish for "good view".
All the better to see you with
The team measured the eye sizes
of many kinds of fossil fishes
and early tetrapods that
lived between 390 million and 250 million years ago to show a dramatic increase
in eye size just before the most advanced fishes, called elpistostegalians,
left the water to evolve into the first tetrapods.
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