This episode is sponsored by Morning Brew.
Morning Brew is a free daily newsletter Monday through Sunday,
and it gets you up to speed on business news in just 5 minutes.
Click the link in the description to subscribe now.
[♪ INTRO]
Often, the bacteria in our guts go pretty much unnoticed
unless, like, you get a stomach bug and feel sick.
But this week, a kind of bacteria got extra attention,
and not for the reason you might think.
It’s called Helicobacter pylori, and scientists used it
to track how ancient humans spread to the Americas from Siberia.
These bacteria have been around for at least 100 thousand years.
And worldwide, it's estimated that up to half the population
has had an H. pylori infection.
This microbe can cause a stomach condition called chronic gastritis,
so it’s something to pay attention to in medicine.
But it’s also a convenient bacteria for other research.
That’s because its genetic sequence varies slightly depending on where the bacteria lives
or rather, depending on where the human they’re infecting lives.
So, this microbe is a great tool for tracking ancient civilizations.
In a study published in the journal PNAS,
researchers sequenced and then analyzed
H. pylori bacteria strains from samples they’d collected from indigenous people
in Siberia and the Americas.
For the analysis part,
they used a technique called Approximate Bayesian Computation
or just ABC for short.
It’s a way of using statistics to determine the likelihood that a hypothesis is true
based on new evidence.
So, in this case,
the researchers were testing scenarios
about where these bacteria might have come from,
and how they could have spread throughout the world.
And by extension,
they were also testing ideas about what that meant for human migration.
Since their methods were based on statistics,
the researchers can’t definitively say what happened in the past.
But their most likely hypothesis was that H. pylori hitched a ride
from Siberia to North America with a small,
single group of humans some 12,000 years ago.
Then, that founder population eventually became
the indigenous people of the Americas,
whose descendants are around today.
As for how this group traveled
well, back then, sea levels were around 100 meters lower than they are now,
so they probably went over a land bridge between Eurasia and North America.
But it’s hard to know exactly why they moved,
because although the world was in a glacial period,
Beringia, the vast supercontinent that contained north-eastern Siberia, Alaska,
and the western parts of Canada, was relatively hospitable.
In fact, this study also found that other people
toughed out the weather and stayed in the area.
There did seem to be a third option, though:
By analyzing these bacteria,
the researchers proposed that another group chose to hang out
in the warmer parts of Eurasia until the glacial period ended about 300 years later.
Then, they joined up in Siberia
with those descended from the group that had stuck around in the north.
Because the Eurasian populations were separated geographically,
their gut bacteria ended up evolving differently.
And now, more than 10,000 years later,
that’s helping us piece together human history.
In other evolution-related news,
scientists have discovered a new species of hyrax in the forests of Africa,
and they did it by listening.
Hyraxes are mammals that kind of look like tubby, scruffy guinea pigs,
with their rounded ears, lack of tails, and stumpy toes.
And aside from their cuteness,
these creatures are known for their distinctive vocalizations,
which sound like shrieking or barking.
This new species was presented in a paper published Tuesday
in the Zoological Journal of the Linnean Society.
It all started when biologists on a field trip noted that hyraxes
on one side of the Niger river sounded different than those on the opposite side.
So, they took 418 recordings of hyrax vocalizations from 42 locations across Africa,
then analyzed how long they were, their pitch, and how often they repeated.
What the researchers heard was that
calls in the area between the Volta and Niger rivers were more like rattling barks,
while those outside that area were more like short, air-horn like shrieks.
After that, the researchers went to museum collections,
and looked at close to 70 hyrax skulls from animals found either
between or outside the rivers.
Turns out, hyraxes who lived between the rivers had shorter,
broader skulls than those outside.
Also, museum specimens, photos,
and carcasses of the animals killed by hunters
revealed that the hyraxes had different coat colors,
as well, with the between-river animals sporting a lighter,
yellow-brown coat streaked with dark brown.
And their outside-the-river cousins sporting a dark brown to almost black coat.
Finally, the researchers peered at the hyraxes’ genetics.
And, sure enough, the two groups had some noteworthy genetic differences.
All those pieces together lead the researchers
to conclude these were two different species.
They called the new species D. interfluvialis -- or “between rivers” in Latin.
And hyraxes aren’t the only mammals who have different species
living between and outside these rivers.
In fact, rivers act as natural barriers many animals can’t cross.
Over time, populations on either side become more and more different until,
eventually, they’re so different that they’re considered separate species.
In other words, these hyraxes are a classic example
of geographic isolation and speciation
all discovered thanks to some barks in the night.
Both studies just go to show how evolution is constant
happening throughout history and around us right now.
Whether the species are gut bacteria or rock-dwelling mammals,
the environment can play a big part
in influencing genetics over hundreds or thousands of years.
And these studies are just the appetizer for all the great things that have happened
this week in science and in other fields, like business!
And keeping track of all of that can be overwhelming,
but today’s sponsor, Morning Brew can help you with some of that.
Morning Brew is a free daily newsletter Monday through Sunday.
It helps you get up to speed on business news in just 5 minutes!
So you can skip skimming through news websites
or just endlessly scrolling on Twitter.
Morning Brew gets all the need-to-know information from business, finance,
and tech together in an accessible format,
and then sends it promptly every morning right into your inbox!
Like on the morning of filming this episode,
they had some fascinating explainers
on Vermont’s high vaccination rate and Texas’s power grid.
If you would like to give it a roll,
it’s completely free and it takes less than 15 seconds to subscribe.
Just click the link in the description below to subscribe to Morning Brew today.
[♪ OUTRO]