A newly discovered broken tetrapod bone means we’ve been on land longer than scientists
thought!
Don’t you just love it when nature throws science a bone?
Hey guys, Amy making bad jokes for you on DNews today.
But jokes aside, bones are pretty useful, not just for giving us the internal stability
to not be goopy piles of flesh and organs but because when they persist over the ages
they give us vital clues as to the history of various species.
It’s from fossilized dinosaur bones that we’ve been able to reconstruct what the
Earth might have looked like long before humans roamed, and going back further it’s from
bones and fossils that we can trace how species evolved.
The fossil record tells us that life started in primitive oceans before the first species
poked their heads out of the water and crawled onto land.
These are so-called transitional species, and scientists have been able to determine
that they first appeared when limbs evolved from fish fins about 360 million years ago
followed by the first land-based tetrapods that showed up around 330 million years ago.
But there’s a pretty big gap in there scientists needed to fill .
To figure out what happened during this 30 million year gap, researchers from the Queensland
Museum in Hendra, Australia, analysed a rare tetrapod fossil from that time period, a nearly
five-foot long Ossinodus that lived about 333 million years ago.
They found from preserved forearm bones that the species could support itself on land.
Whether or not it did was a different story, and that evidence came from what might be
the oldest known broken bone.
In studying the broken bone, the team used computer software to reconstruct the forces
required to cause the break.
Turns out, it’s a lot of force, much larger than the animal itself.
Because water acts as a cushion, there’s no way such a bad break could happen under
water.
The transitional animal that left that broken bone behind must have been on land.
far too much to have break one of the break, they found the magnitude of the force was
so large relative to the size of the animal that the accident must have occurred on land.
From reconstructing the break, the team concluded that the animal likely fell from a rock or
log about three feet off the ground.
Of course, they can’t be sure, but it’s pretty probable given the bone-based evidence.
So if the Ossinodus broke a bone on land, it must have spent at least some time out
of the water, and that makes it the oldest known tetrapod to be fairly well adapted to
life on the land, getting us one step closer to nailing down the moment when animals first
left the water.
Scientists are always learning more about how we evolved to be the complex creatures
we are today.
But is it possible for evolution to reverse itself?
Julia discusses that idea in
this episode: