This episode is brought to you by the song
Like This Patrick Olsen’s new release single. You can check out the link in the description
to start listening. [♪ INTRO] Imagine taking a nap at a time when woolly mammoths roamed the plains… and then waking up in the twenty-first century. That may sound like a science fiction story, but it might be the real experience of tiny
aquatic animals called rotifers. According to a report in Current Biology, these little creatures can survive being frozen
in ice for at least twenty-four thousand years. Seems like too long. Rotifers are microscopic invertebrate animals, usually less than one millimeter long. They live in wet environments all over the
world, including moist soils. And we already knew that they could survive
being frozen. Experiments have shown that rotifers can remain
frozen for up to ten years before thawing out and just continuing to
live their tiny lives. But maybe ten years is nothing for a frozen
rotifer. Researchers found these Rip Van Rotifers in
a sample of frozen soil, or permafrost, from northeastern Siberia. The soil sample came from three and a half
meters underground, and radiocarbon dating estimated it to be around twenty-four thousand years old. Like, imagine sleeping so long you have to
be radiocarbon dated when you wake up. When the researchers thawed the soil, they
found living rotifers inside. Now, it’s possible for something as small
as a rotifer to have like maybe snuck into the soil after it originally
froze, or even during the sample collection, but the scientists claim this is not the case
here. First, because the icy soil is solid enough that even something as tiny as a rotifer shouldn’t have been able to squeeze in. And second, because they identified fragments
of DNA within the frozen soil that matched with the
rotifers. This evidence seems to suggest that the tiny animals were frozen all that
time. Yet, these rotifers weren’t only able to
keep on living, they began reproducing. Since rotifers reproduce asexually, that meant
the researchers had a convenient culture of rotifer clones
to study. They were able to compare these ancient rotifers’
DNA to more modern specimens, and it looks like they are probably distinct from the rotifers wiggling around today. And they were also able to run a series of
experiments, re-freezing the cloned rotifers and showing
that they are fully capable of surviving being slowly frozen into ice. Like many other rotifers, they appear to have
some sort of mechanism that prevents their cells and tissues from
being damaged or destroyed by ice crystals, though researchers don’t know how that works
yet. Amazing as all of this sounds, these aren’t
the first multicellular organisms reported to survive thousands of
years of deep freeze. A 2018 study reported a pair of nematode worms that survived being frozen in permafrost for
over thirty thousand years. And a 2012 study reported plant seeds that
were able to germinate after being frozen for nearly thirty-two thousand
years. Now, it’s worth pointing out that these
previous studies have drawn skepticism from other scientists, who worry that they haven’t fully ruled
out the possibility of contamination by modern organisms. But it’s definitely true that rotifers and
other organisms can survive being frozen for long periods
of time … possibly very long periods. Scientists are hopeful that studying these
organisms might help us develop better techniques for storing frozen
tissues and organs. So if you’re clinging to the sci-fi dream
of freezing yourself for thousands of years into the future, the secret to success might be held within
these tiny invertebrates. And if those rotifers really were frozen for
twenty-four thousand years, they totally slept through a major historical
event the domestication of goats! That’s right, that was our transition. Humans started domesticating crops and livestock around ten thousand years ago, and it was a pretty big deal for us as a species. Goats were one of the ones we started with. But there’s a lot we don’t know about
the early parts of that process. And now that picture is a little bit clearer. A new study in the journal PNAS reports ancient
goat DNA from a time when they were just beginning
their path to domestication. The DNA samples come from remains of goats in two archaeological sites in the Zagros
mountains of western Iran, dating to about ten thousand years ago. Researchers were able to sequence DNA from thirty-two goats at these sites. To date, these are the oldest livestock genomes
ever sequenced. The results show a group of animals that were
not fully wild, but weren’t fully domesticated yet either. The physical remains of these goats look a
lot like their wild cousins, with large bodies and big, scimitar-shaped
horns. And their DNA is lacking some of the genetic
signs associated with domestication, including changes in genes linked to coat
color. But they were clearly on the way the analysis found that most of these ancient
goats represent an early branch of the domestic
goat lineage. Amazingly, these goats’ DNA held clues to how humans were managing them a mixture of modern and ancient practices. See, some of the sampled goats were genetically very similar to wild goats, so it seems that humans of the time were still
in the habit of capturing wild goats to add to their herds. But on the other hand, the Y chromosomes of
these goats, which are passed down by males, were much less diverse than mitochondrial
genomes, which are passed down by females. This suggests the ancient herders were in
the habit of culling most males and reserving only a select
few for breeding, a practice still used today by goat herders
of that region, and also by animal breeders all over the world. Altogether, this reveals a picture of a transitional
period in goat domestication. Ten thousand years ago, humans were already managing goats as livestock, using some of the same strategies as today. But it would still be some time before they
were the domesticated animals we know today: crucial sources of food, milk, and also hilarious
internet videos. But in addition to hilarious videos, the Internet
also has music. And today’s sponsor, Music for Scientists
by Patrick Olsen, has a bunch of songs you can choose from. Such as the new single, Like This! This is a fun catchy single that focuses on
our place on Earth. It’s a total banger that’s all about seeing very familiar things in new ways. If you want to check this new single out, check out the link in the description to start
streaming Like This by Patrick Olsen. [♪ OUTRO]
