Thanks to Brilliant for sponsoring this whole week of SciShow!
You can learn more at Brilliant.org/SciShow.
[ ♪INTRO ]
We used to think that carbs were a recent addition to the human diet.
I mean, that’s why the so-called “Paleo diet” says you shouldn’t eat wheat or potatoes.
But perhaps unsurprisingly, the fad diet trend doesn’t really capture the science of what people used to eat.
And just last week, a new study published in the Journal of Human Evolution further proved that.
You see, the researchers found smoking-gun evidence that says humans have been eating
starches for over a hundred thousand years.
Up until recently, the general assumption was that early hominins were top-level carnivores
whose diet was mostly meat.
It was thought that our species only started to buck this trend around 10,000 years ago
when agriculture became widespread.
But more recent studies have cast doubt on this idea.
For one thing, our genes seem to suggest we were eating starch a long time ago.
Take the gene AMY1, for example, which encodes the protein amylase.
That’s an enzyme produced in your saliva which helps break down starches into simple sugars.
Great apes, and older lineages of human like Neanderthals and Denisovans, have two copies of this gene.
But you, my friend, have as many as twenty copies of it.
There is no reason for our species to have made and kept so many copies of this gene
if we weren’t consuming starches.
These copies aren’t new, either — an 8,000-year-old hunter-gatherer was found to have 13 copies of this gene.
And that much duplication doesn’t happen overnight.
Analyses suggests they’re hundreds of thousands of years old, which would mean that adaptation
to a starch-rich diet was already happening long before agriculture took hold.
Archaeological studies also lend a bit of support to this idea.
Charred food remains suggest humans cooked oats, wild peas, and root vegetables some
65,000 years ago, for example.
And archaeologists have also found starch granules in the fossilized teeth of both Neanderthals
and modern humans from around 50,000 years ago.
There’s even evidence of people making bread or something like it 4,000 years before the advent of agriculture.
But last week, an international team of archaeologists announced the oldest find yet: charred remains
from plant starches dating as far back as 120,000 years ago.
These were found in ancient hearths from the Klasies River Cave in southern South Africa.
It wasn’t just obvious what the charred bits were, though.
The scientists had to examine them closely with an electron microscope.
That’s an instrument that uses electrons in place of light to look at specimens in
a much higher magnification than traditional light-based microscopes.
With it, the researchers were able to identify burned bits of roots and tubers — vegetable
varieties akin to modern yams and potatoes.
In other words, starches.
This find is the earliest yet showing that humans were cooking and eating starch long
before agriculture was a thing.
This helps explain the existing evidence of ancient starch consumption from our genomes,
and it basically closes the book on other theories.
We weren’t simple meat-eaters back in the Paleolithic.
Humans have loved carbs for a very, very long time.
And judging by how I feel about a can of Pringles, this makes sense.
But while one genetic mystery seems to be solved, on Tuesday, scientists announced that
they’ve uncovered a new one.
They found a lineage of yeast that has lost a bunch of genes supposedly required for life.
And yet...it’s alive.
The yeast in question is a genus called Hanseniaspora, which is used a lot in winemaking.
During the early stages of wine fermentation, Hanseniaspora will multiply like crazy.
And even when winemakers use multiple types of yeast, varieties of this yeast grow so
fast that they can end up being 80% of the final yeast population.
And it’s not just a fast grower — it’s a fast evolver.
When scientists analyzed the genomes of many types of yeast, they found that a lot of the
species in this genus experience rapid genetic changes in a relatively short amount of time.
So scientists at Vanderbilt University and University of Wisconsin-Madison decided to take a closer look.
And they were astonished to find species without really important genes.
You see, from a biological perspective, some genes are considered more important than others.
Like, the genes that code for proteins involved in cell division, for example.
These are really old genes that have changed very little over time — presumably because
changes to them don’t generally work out so well.
So they’re thought to be super important — even essential for life.
And accordingly, they can be found in pretty much every living thing ever — except, for Hanseniaspora.
The researchers identified two varieties of this yeast which had completely lost dozens
of genes, including ones involved in cell division and DNA repair.
One had branched off into a new lineage about 87 million years ago and evolved quickly,
while the other branched off about 54 million years ago and evolved more slowly.
And the fast-evolving lineage lost the most.
For example, both lineages lost WHIskey 5, which helps regulate cell size during cell
division, and MAG1, which plays a role in removing damaged DNA bases.
But the fast-evolving lineage also lost a bunch of other genes that keep cells from mutating.
During the process of cell division, there are various checkpoints that make sure the
steps toward division have been completed correctly before things are allowed to proceed.
The fast-evolving lineage lost several of the genes involved in these checkpoints.
This simply isn’t supposed to happen.
Letting DNA mutate without repair and cells divide without oversight should lead to fatal
changes occurring relatively quickly — but somehow this lineage has survived.
The scientists think that other genes may be picking up the slack for the genes that were lost.
As for why these species would want to mutate so rapidly, the researchers pointed out many
organisms go through periods of rapid mutation when the world they live in changes.
So, it’s possible that a rapidly changing environment in Hanseniaspora’s past gave
the fastest mutators an evolutionary advantage.
And that may mean that, when it comes to evolutionary strategies, losing genes could be as effective
for adaptation as making new ones.
The researchers hope that studying this fast-evolving mutant yeast can teach them more about the
basic processes that govern life.
One thing’s for sure though: many of the genes we thought were essential aren’t.
I guess Ian Malcolm was right: Life, uh, finds a way.
It took some hardcore genomics research to figure out what these yeasts’ genomes looked like.
And if you want to better understand how that research is done, you might want to check
out Brilliant.org.
Their course on Computational Biology, for example, can help demystify genomics research.
You’ll learn the science behind genotyping and ancestry analysis, among other things.
And that’s just one of their in-depth interactive courses — they have dozens covering topics
in math, science, engineering, and computer science.
All of them are designed to be hands-on, with animations and quizzes to help guide your
understanding the whole way through.
And their iOS app lets you download your courses to work through later.
Plus, the first 200 people to sign up at Brilliant.org/SciShow will get 20% off the annual Premium subscription.
That unlocks all of their daily challenges in the archives in addition to the actual courses.
And you’ll be supporting SciShow while you learn.
So, thanks for that!
[ ♪OUTRO ]