MALE NARRATOR: In 1973, a fossil hunter discovered the partial skeleton of a female Homo erectus in the Koobi Fora formation of northern Kenya.

The specimen was 1.6 million years old.

Today she is known as KNM-ER 1808.

Her skeleton was pretty complete given its age, including parts of her skull, limbs, and pelvis.

And the anthropologist 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 have been very painful, and ultimately fatal.

But what could have caused this condition?

Oddly, it looks like it might have 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.

I'm talking peeling skin, gastrointestinal problems, a risk of seizures, and then bone pain and swelling.

And those original researchers thought that the most likely way that this poor Homo erectus got a hold 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 came with some serious risks, as that poor 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 of our success as a species has been our early and sometimes fatal experimentation with food.

[MUSIC PLAYING] 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 that meat and other high-quality foods, like fat and bone marrow, probably became a bigger part of diets 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 two 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 their prey, scavenging it from other predators posed its own problems.

They'd have to get 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 their predator off of its kill.

And neither option was particularly safe.

OK.

So what about fish?

Less risky than trying to scare a lion off of 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 have 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 that 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 have 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 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.

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 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 6,300 and 3,800 years ago.

It found that the bones of codfish 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 have found out the hard way.

So, anthropologically speaking, there is no such thing as a single so-called "paleo diet."

We've made the best with whatever has been available.

But we also know that, on the individual level, at least, being an adventurous eater could be risky business.

[MUSIC PLAYING]