The Risky Paleo Diets of Our Ancestors

In 1973, a fossil hunter discovered the partial skeleton of a female Homo erectus in the Koobi Fora formation of northern Kenya. The specimen dates back to 1.6 million years ago; Today she is known as KNM-ER 1808. Her skeleton was quite complete, given her age, including parts of her skull, limbs, and pelvis. And 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 rough, with irregular areas of new bone growth. That thick 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 enough, it looks like it may have been something she ate. The researchers who originally studied the bones considered several possibilities and no diagnosis fit perfectly. But they finally settled on one that's pretty uncommon today: an overdose of vitamin A. While vitamin A is usually good for us, helping us with color vision and a healthy immune system, in doses High levels can cause toxicity and a painful death. We're talking peeling skin, gastrointestinal problems, and an increased risk of seizures, plus bone pain and swelling.

And those original researchers thought that the most likely way for this poor Homo erectus to get that much vitamin A was by eating carnivore livers. Now, just like us, our hominid

ancestors

could (and did) eat just about anything. But the downside to this is that it carries serious risks, as Homo erectus discovered. We can trace our history of eating almost anything through the fossil record and see the impact it has had on our evolution. And when we do, we see that our adventurous eating habits allowed us to expand our

diets

and live almost everywhere. The fact is, there has never been a single

paleo

diet.

But over time, part of the secret to our success as a species has been our early – and sometimes fatal – experimentation with food. The taste for meat was probably disastrous for Kenyan Homo erectus, but it has been very important for our genus as a whole. Our earliest hominid relatives, such as Australopithecus anamensis and Paranthropus boisei, likely had plant-based

diets

. Likewise, our closest living relatives, chimpanzees and gorillas, eat many of what we consider "low-quality" foods: things that are not high in calories, such as grasses, leaves, and green fruits. And they only get small amounts of animal protein from insects and occasionally a piece of meat.

But we think that meat and other “high-quality” foods, such as fat and bone marrow, probably became a more important part of the diet early in the history of our genus, Homo. But there is still some debate about who started eating meat first. The oldest widely accepted evidence of meat eating comes from cut-marked bones found at the site of Gona, Ethiopia, about 2.5 million years ago. The hominids there, probably members of some of the earliest species of Homo, were capable of decomposing animal carcasses. But we don't know how much meat they ate, or whether they hunted their own prey or simply foraged for food in the trash.

So sites like Gona show us that hominids could get meat, but it's hard to know how often they ate it. Another site, called Kanjera South in Kenya, is the first to show the earliest 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 includes bones that have been cut. drilled or opened with stone tools over hundreds of thousands of years. So our

ancestors

clearly ate meat and marrow quite frequently by then. But getting that meat carried serious risks. Aside from the inherent threat of being injured during a hunt, there are other dangers, such as wasting precious energy.

Even today, studies of many modern hunter-gatherer groups show that hunts often fail, even when they use things like projectile weapons. And even if those ancient hominids weren't hunting prey, taking it from other predators posed its own problems. They would have to get to the carcass fast enough to steal some meat before it spoiled or, if they were feeling less patient, they would have to try to scare the predator away from its prey. And neither option was particularly safe. Well, what about the fish? Less

risky

than trying to scare a lion away from 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 hominids there were fans of seafood. Among the animal remains found at the site were fossils of catfish and turtles, pleasant and safe prey. But crocodile fossils were also found there. So being attacked by a crocodile while searching for fish or turtles would have been a very real danger. So, in terms of the calories and nutrients it provided, the meat was worth it. But it was definitely

risky

to get it. That's why our ancestors also continued to eat plants.

And although they seem less dangerous to find and eat, plants have their own fun and unexpected ways of trying to kill us, or at least make us very sick. Many plants, including green tomatoes, contain toxins that act as chemical defenses against consumption. But you would only feel the negative effects if you ate A LOT at once. To avoid this, some animals eat many different plants a day. And one of the distinctive characteristics of our gender, as we have evolved, is eating a more varied diet. For example, a study of carbon isotopes in the fossils of several early Homo species showed that they sometimes ate larger plants, such as shrubs and leafy trees, but also ate terrestrial plants such as grasses and sedges.

Being willing to eat different plants made us more versatile and helped us avoid getting poisoned from eating too much of the same thing. And by continuing to eat vegetables, we gave ourselves some backup options, in case we failed at hunting or scavenging. Therefore, many of the plant-based foods that we might consume today, such as cashews or beans, posed serious risks in the past if consumed raw. But we managed to survive as a species, somehow. And there's one more thing that millions of people around the world eat today, and that our ancestors probably enjoyed, even though it would have been painful to acquire.

I am referring to insects and the products that some of them make, such as honey. Insects are often overlooked as potential food in the fossil record because they don't leave much obvious evidence. Additionally, since most anthropologists historically come from cultures that do not eat insects, they did not consider them food. And honey is also pretty invisible in the fossil record, although we do have evidence of fossil bee nests at a hominid site in South Africa. But we know that our great ape relatives today eat insects and honey. And eating insects has its advantages: They are fairly easy and safe to obtain, and they are unlikely to transmit pathogens to us the way meat taken from the garbage would.

They are also a good source of protein, fat and micronutrients. And honey is incredibly energy dense. But how can we know if our hominid 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 wear patterns on those tools suggest they may have been used to dig into termite mounds. And we know that there were termites there because animals that feed on termites have been found there. And there is also evidence of termite damage in animal fossils from the site; Yes, apparently some termites seem to eat bones, perhaps because of the nitrogen.

But there is a debate about who made those bone tools, because there we have found fossils of both Homo and Paranthropus robustus. Now, while insects are pretty easy to catch, some of them have pretty nasty defenses, like venom, or fierce stingers, or powerful bites, so there was also a risk for our hominid ancestors. Honey has the obvious disadvantage of having to deal with bees. Not to mention the possibility of falling from 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 around the world, depending on what is available and what different cultures have been like.

But we have 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 number of sites in Norway dating back to between 6,300 and 3,800 years ago. He found that cod bones contained huge amounts of naturally occurring toxic metals: more than 20 times the amount of cadmium and up to four times more lead than is considered safe today. The fish was toxic, but people ate it anyway. So our willingness to eat almost anything is a hallmark of human history, dating back to our earliest hominid relatives.

We have ingested almost everything we could find: insects, mammals, reptiles, fish, birds, plants and animal by-products such as honey. And so did hominids like Homo erectus. But it didn't always work for us, as KNM-ER 1808 may have found out the hard way. So, from an anthropological point of view, there is no single so-called

paleo

diet. We have done the best with everything that was available. But we also know that, at least on an individual level, being an adventurous eater can be risky business. OK, if this episode made you hungry for more human evolution content, be sure to check out our human evolution learning playlist.

You will learn the basics of what we know and what we are still discovering about the evolution of Homo sapiens. And many thanks to this month's eontologists: Patrick Seifert, Jake Hart, Jon Davison Ng, Sean Dennis, and Steve. And as always I want to thank you for joining me at the Konstantin Haase Studio. Be sure to subscribe at youtube.com/eons for more evolving adventures.