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Dinosaur evolution seems pretty straight forward.
Creepy lizardish thing, to creepy raptor thing, to slightly less creepy chicken.
but what if evolution reversed itself?
Hey everyone, Julia here for DNews,
Dollo’s law, named after 19th century Paleontologist Louis Dollo, states that once a structure
is lost in evolution, it’s lost forever.
But sometimes, on a rare occasion, the past pops back up.
Researcher Alexander Vargas and others from the University of Chile who analyzed modern
birds discovered one such case.
They found an ancestral wrist bone may have made a comeback.
The ancestors of some dinosaurs walked on all fours and needed strong wrists with 11
bones to support their weight.
One of these bones is called the PIE ZAH FORM pisiform.
When some dinosaurs started walking on just two legs, the wrists changed.
They weren’t so good for getting around, but they were pretty good at tearing apart
prey.
In the change they lost some weight and some bones.
This wrist had just 3 bones.
The pisiform either disappeared or became so soft it left no trace in the fossil record.
When dinosaurs took to flight, the wrist changed again to be more flexible wing.
These early bird-like raptors evolved a different type of wrist bone, the ulnare.
To figure out the fate of the missing bone, the researchers examined evidence from both
the fossil record and from the development of modern bird embryos.
In developing embryos, they used a tracking technique using stains to see how the bones
formed.
Looking at the more modern birds, the researchers noticed the ulnare was suspiciously present
in the early stages of development but wasn’t present in fully grown birds like previously
thought.
But there was a bone there in adult forms.
Upon closer inspection, it was really the old missing pisiform back again.
The researchers think the reemerging bone is the result of vestigial genes.
Vestigial limbs or organs, like our tailbone or appendix are traces of the past.
They are the remains of parts that are no longer evolutionary advantageous so they either
disappear into our history or become almost useless.
Over the millennia the genes that coded for the pisiform were still there, just dormant.
And when they were expressed again, they were no longer good for walking around on all fours,
but for flying.
So the bone appeared, disappeared and reemerged to perform a different function, which is
a radical concept for scientists.
The idea of evolutionary reversal is still met with resistance.
It goes against Dollo’s law, which treats evolution like a one way street.
Even though several cases of reversal happening have been identified.
Like teeth reemerging in some South American frogs after 200 million years of absence.
This recent research is just one piece of a puzzle that could turn one of the most closely
held scientific concepts on its head.
It’s cool, it’s weird, it’s evolution.
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What do you think?
Can evolution reverse itself?
What if one day our descendents get their tails back?
Leave a comment below.
To learn more about the dinosaur to bird evolution, let trace tell you in this video.
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