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This week in news, a discovery in genetics that was once thought unbelievable, and a parrot so large that it shakes up what we know about avian evolution.

Hosted by: Hank Green

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Sources:

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3000166
https://www.nationalgeographic.com/news/2013/6/130626-ancient-dna-oldest-sequenced-horse-paleontology-science/
https://www.nature.com/scitable/definition/ribonucleic-acid-rna-45

https://royalsocietypublishing.org/doi/10.1098/rsbl.2019.0467
https://www.eurekalert.org/emb_releases/2019-08/fu-nbb080219.php


https://en.wikipedia.org/wiki/File:Giant_Haasts_eagle_attacking_New_Zealand_moa.jpg#/media/File:Giant_Haasts_eagle_attacking_New_Zealand_moa.jpg


https://commons.wikimedia.org/wiki/File:Kakapo_Sirocco_1.jpg
[intro].

In a new study published this week in the journal PLOS Biology, molecular biologists describe something unbelievable: the sequence of the oldest RNA discovered to date. This RNA is estimated to be a little over fourteen thousand years old.

Its very existence challenges the long-held belief that ancient RNA just isn’t a thing. And it suggests there could be lots of RNA waiting to be discovered in ancient remains. Now, fourteen thousand years might not sound that impressive.

After all, a couple of years ago, scientists were able to sequence the entire genome of a seven hundred thousand year-old horse. But that was DNA—the molecular blueprint inside cells. And though DNA starts to break down when a cell dies, under certain circumstances, it can be preserved for thousands of years.

RNA is thought to be much more temporary—and that’s by design. One of its main jobs is to carry the instructions written in DNA to the cell’s protein-making factories— a process which, ideally, is pretty quick. Once those instructions have been delivered, an army of enzymes goes after the RNA to break it down and get it out of the way.

And because it’s chopped up so quickly, many researchers have long assumed there’s no point to looking for RNA in samples that are hundreds or thousands of years old. Except, recent studies have suggested ancient RNA may exist after all. So, the authors of the new study decided to look for it in some exceptionally well-preserved canine remains.

Two of their samples were skins from wolves shot in Greenland in the 1800s and 1900s. The third was a sample of tissue from a “puppy” found in frozen Siberian soil which was carbon-dated to around 14,000 years old. And amazingly, the researchers were able to find and determine the sequences of RNAs from all three specimens.

They could even tell what type of tissue they sampled based on the RNA! The Siberian sample now has the honor of being the oldest RNA known to science by about nine thousand years, and the oldest sequenced by over 13,000 years! And that’s especially exciting because.

RNA can tell us things that DNA can’t. For example, because it reflects what a cell is doing at a given moment in time, it could reveal what conditions an organism was experiencing when it died, and even hint at the cause of death in cases where there’s no obvious physical trauma. There are also some viruses that lack DNA, like HIV and influenza.

These are super significant for modern medicine, so it’d be great to see how their sequences have changed over time or identify their presence in an ancient body. But that’s basically impossible without ancient RNA, because these viruses often don’t leave any other trace in the archaeological record. But it remains to be seen whether ancient RNA is actually all that common.

The authors pointed out that this Siberian sample was particularly well-preserved, and such remains are quite rare. Still, they’re hopeful that there’s more ancient RNA hidden in the frozen soils of places like Canada, Alaska, and Antarctica. And it doesn’t have to come from soft tissues.

Bones, keratin, even plant seeds could potentially be untapped reservoirs for millennia-old RNA. Speaking of big surprises from the past... Paleontologists announced this week that they’ve unearthed a giant parrot in New Zealand— the first giant parrot known to science.

Today, the biggest parrot in the world is the kakapo, a nocturnal flightless species native to New Zealand. You may have seen this bird having sex with Stephen Fry’s camera man’s head. That’s why I know it mostly.

They can weigh up to 3 kilograms, which is about twice the weight of the biggest macaw. But that’s downright wee compared to Heracles inexpectatus, the fossil parrot researchers described this week in a paper in the journal Biology Letters. The fossil was found in rocks dated to the Early Miocene Epoch, between nineteen and sixteen million years ago.

Still, unique features of those bones made it clear they came from a member of the parrot branch of the bird family tree. And the team was able to calculate weight and height estimates based on the relationship between leg proportions and body size in birds. That math suggests this bird weighed a colossal seven kilograms and stood about a meter tall.

Of course, with just leg bones to work with, it’s hard to say much about this Herculean parrot’s daily life. But at that size, it’s a safe bet that it was flightless. And it was probably doing the same thing that most enlarged birds on islands do: taking over unoccupied environmental niches.

You see, evolution does weird things in isolation, and one of them is to make small animals big. It’s a phenomenon known as insular gigantism. And the fossil record is full of examples of birds that got big on islands: oversized ducks in Hawai’i, giant storks in Indonesia, and the dodos of Mauritius, just to name a few.

But New Zealand really takes the cake for big bird diversity. It’s been home to giant geese, humongous eagles, and the famous moas in addition to the world’s biggest parrots. These birds were able to achieve such large sizes because the islands were basically devoid of the sizable predators and plant-eaters that lived on the mainland.

So, in the diverse subtropical forest of Miocene New Zealand, there would have been lots of open opportunities for a big bird to take up browsing on vegetation, or perhaps step into other roles normally filled by medium-sized mammals. Some have even speculated this parrot-zilla may have eaten other parrots! But, there’s no actual evidence of that... yet.

Truth is, we won’t know what they ate or how big they really got until we find more fossils. Such finds could also shed light on the birds’ relatives— researchers aren’t sure if Heracles is a close cousin of the kakapo or a separate instance of gigantism in parrots. Either way, these jumbo parrots shake up what we thought we knew about parrot evolution.

And hopefully, more fossils will help us flesh out this unexpected titan. Thanks for watching this episode of SciShow News! And a special, giant thank you to you, SR Foxley—today’s President of Space.

Your continued support of this channel makes a colossal difference. So does the support of all our patrons— so thanks, all of you! And if you’re not a patron, but you think what we do here is good and would like to help us do it, you can learn more about joining our community of supporters at Patreon.com/SciShow. [ outro ].