In 1973, a fossil hunter discovered the partial skeleton of a female Homo erectus in the Koobi
Fora formation of northern Kenya.
The specimen dated to 1.6 million years ago; today she’s known as KNM-ER 1808.
Her skeleton was pretty complete, given its age, including parts of her skull, limbs,
and pelvis.
And the anthropologists who studied her remains quickly noticed that there was something strange
about the bones of her legs and arms.
The texture of her bones was coarse, with patchy areas of new bone growth.
That coarse layer was evidence that something had seriously disrupted the normal functioning
of her bone cells before she died.
This would’ve been very painful, and ultimately, fatal.
But what could have caused this condition?
Oddly enough, it looks like it might’ve been something she ate.
The researchers who originally studied the bones considered several possibilities, and
no diagnosis was a perfect fit.
But, they eventually settled on one that’s pretty uncommon these days: an overdose of
vitamin A.
While Vitamin A is usually good for us, helping us with color vision and healthy immune systems,
in high doses it can cause toxicity and a painful death.
We’re talking peeling skin, gastrointestinal problems, and an increased risk of seizures,
along with bone pain and swelling.
And those original researchers thought that the most likely way that this poor Homo erectus
got ahold of that much vitamin A was by eating the livers of carnivores.
Now, like us, our hominin ancestors could - and did - eat pretty much everything.
But the downside of this is that it comes with serious risks - as that Homo erectus
found out.
We can track our history of eating just about anything back through the fossil record and
see the impact it’s had on our evolution.
And when we do, we see that our adventurous eating habits allowed us to expand our diets,
and enabled us to live almost everywhere.
So the fact is, there’s never been just one paleo diet.
But throughout time, part of the secret to our success as a species has been our early
- and sometimes fatal - experimentation with food.
A taste for meat was probably disastrous for that Homo erectus in Kenya, but it’s been
a big deal for our genus as a whole.
Our early hominin relatives, like Australopithecus anamensis and Paranthropus boisei, probably
had plant-based diets.
Likewise, our closest living relatives, chimpanzees and gorillas, eat lots of what we consider
“low quality” foods - things that aren’t calorie-dense, like grasses, leaves and unripe
fruit.
And they only get small amounts of animal protein from insects and the occasional bit
of meat.
But we think meat and other “high quality” foods, like fat and bone marrow, probably
became a bigger part of the diet early in the history of our genus, Homo.
But there’s still some debate about who started eating meat first.
The earliest widely-accepted evidence of meat-eating comes from cut-marked bones found at the site
of Gona, Ethiopia from about 2.5 million years ago.
The hominins there - probably members of some early Homo species - were capable of breaking
down animal carcasses.
But we don’t know how much meat they ate, or if they were hunting their own prey or
just scavenging.
So, sites like Gona show us that hominins could get meat, but it’s hard to tell how
often they ate it.
Another site, called Kanjera South in Kenya is the first to show early members of our
genus -- most likely Homo habilis or Homo erectus - eating meat on a regular basis
The site dates back 2 million years, and it includes bones that have been cut into or
broken open with stone tools spanning hundreds of thousands of years.
So our ancestors were clearly eating meat and marrow pretty often by then.
But getting that meat came with serious risks.
Aside from the inherent threat of getting injured during a hunt, there are other dangers
- like wasting precious energy.
Even today, studies of many modern hunter-gatherer groups show that hunts often fail - even when
they’re using things like projectile weapons.
And even if those ancient hominins weren’t hunting the prey, scavenging it from other
predators posed its own problems.
They’d have to get to the carcass quickly enough to steal some meat before it went bad,
or, if they were feeling less patient, they’d have to try to drive the predator off of its
kill.
And neither option was particularly safe.
Okay, so what about fish?
Less risky than trying to scare a lion off a wildebeest carcass, right?
Well in 2010, a site from that same Koobi Fora formation in Kenya showed that, about
1.95 million years ago, the hominins there were fans of seafood.
Among the animal remains found at the site were fossils of catfish and turtles - nice,
safe prey.
But there were also fossils of crocodiles found there.
So getting attacked by a croc while foraging for fish or turtles would’ve been a very
real hazard.
So, in terms of the calories and nutrients
it provided, meat was worth it.
But it was definitely risky to get.
Which is why our ancestors kept eating plants, too.
And while they seem less dangerous to find and eat, plants have their own fun, unexpected
ways of trying to kill us, or at least make us really sick.
Many plants, including things like unripe tomatoes, contain toxins that act as chemical
defenses against being eaten.
But you’d only feel the negative effects if you ate a LOT of it at once.
To avoid this, some animals feed on a lot of different plants in a day.
And one of the hallmarks of our genus, as we’ve evolved, is eating a more varied diet.
For example, one study of carbon isotopes in the fossils of several early Homo species
showed that they sometimes foraged from bigger plants like leafy bushes and trees, but also
ate ground plants like grasses and sedges.
Being willing to eat different plants made us more versatile and helped us avoid getting
poisoned by eating too much of the same thing.
And by continuing to eat our veggies, we gave ourselves some backup options, in case we
failed at hunting or scavenging.
So, many of the plant-based foods we might snack on today -- like cashews or kidney beans
-- came with serious risks in the past if they were consumed raw.
But we managed to survive as a species - somehow.
And there’s one more thing that millions of people all over the world eat today, which
our ancestors probably enjoyed, even though it might’ve been painful to acquire.
I’m talking about insects and the products that some of them make, like honey.
Bugs are often overlooked as a potential meal in the fossil record because they don’t
leave behind a lot of obvious evidence.
Also, since most anthropologists have historically come from cultures that don’t eat insects,
they weren’t thinking of them as food.
And honey is pretty invisible in the fossil record, too, though we do have evidence of
fossil bees’ nests from one hominin site in South Africa.
But we know that our great ape relatives today eat both insects and honey.
And eating bugs has its advantages: they’re pretty easy and safe to get, and they’re
unlikely to give us pathogens the way scavenged meat could.
They’re also a good source of protein, fat, and micronutrients.
And honey is incredibly energy-dense.
But how can we tell if our hominin relatives ate insects?
Researchers have analyzed bone tools from the site known as Swartkrans
in South Africa, which dates back 1.8 million years.
And the patterns of wear on those tools suggest that they may have been used for digging into
termite mounds.
And we know that termites were there because animals that eat termites have been found
there.
And there’s also evidence of termite damage on animal fossils from the site; yeah apparently,
some termites seem to eat bone, maybe for the nitrogen.
But there’s a debate about who made those bone tools, because we’ve found fossils
of both Homo and Paranthropus robustus there.
Now, while bugs are pretty easy to catch, some of them have pretty nasty defenses, like
venom, or vicious stingers or powerful bites - so there was risk for our hominin ancestors,
too.
Like, honey comes with the obvious downside of having to deal with bees.
Not to mention potentially falling out of the tall trees where some African bees make
their hives, which is a real risk for modern hunter-gatherers who collect honey today.
So, both now and in the past, human diets have varied all over the world, based on what’s
available and what different cultures have been like.
But we’ve always been very willing to take risks for anything that might be tasty.
Even in recent history!
For example, a study published in 2020 reported on a series of sites in Norway that dated
from between 6300 and 3800 years ago.
It found that the bones of cod fish there contained huge amounts of naturally occurring
toxic metals -- more than 20 times the amount of cadmium and up to four times as much lead
as is considered safe today.
The fish was toxic, but people ate it anyway.
So, our willingness to eat almost anything is a hallmark of the human story, going back
to our earliest hominin relatives.
We’ve ingested nearly everything we could find, insects, mammals, reptiles, fish, birds,
plants, and animal byproducts like honey.
And so did hominins like Homo erectus.
But it didn’t always work out for us, as KNM-ER 1808 might’ve found out the hard
way
So, anthropologically speaking, there’s no such thing as a single so-called paleodiet.
We’ve made the best with whatever’s been available.
But we also know that, on the individual level at least, being an adventurous eater could
be risky business.
OK if this episode got you hungry for more human evolution content, be sure to check
out our Human Evolution Learning Playlist.
You’ll learn the fundamentals about what we know, and what we’re still discovering,
about the evolution of Homo sapiens.
And a big thank you to this month’s Eontologists:
Patrick Seifert, Jake Hart, Jon Davison Ng, Sean Dennis, and Steve!
And as always I wanna thank you for joining me in the Konstantin Haase Studio.
Be sure to subscribe at youtube.com/eons for more adventures in evolution.