Miki Ben-Dor: The complete and unifying explanation of human evolution (Part 1)
Welcome to Part 1 of our journey!
Here’s a link to Miki’s Google Scholar page so you can grab the paper. Look for the following title:
Strap on your nerd hats, my friends - this is going to be fun!
Starting with the Abstract
We can get a lay of the land by starting with the Abstract. Here’s an excerpt:
Humans consumed megaherbivores, including proboscideans, throughout the Pleistocene. However, there is a high potential for underappreciation of their relative importance to humans’ economy due to their potential relative underrepresentation in Palaeolithic archaeological sites.
Relying on our previous work, we discuss the critical importance of large animals in human prehistory. We review four factors that made megaherbivores critically important to humans: high ecological biomass density, lower complexity of acquisition, higher net energetic return, and high fat content.
We propose a model that intends to overcome the potential underrepresentation bias by multiplying the MNI (Minimum Number of Individuals) of each animal species by its weight and only then determining the relative biomass abundances.
The next step of the model is the accumulation of the relative biomass abundance, beginning with the largest animal. This step enables a comparison of various assemblages in the relative complexity of acquisition, the level of net energetic return, and the level of fat content in the prey.
Let’s cover a few terms that may be unfamiliar:
Zooarchaeological assemblages - Also called a faunal assemblage; this is a group of associated animal fossils found together in a given stratum. (Note that zooarchaeology is the branch of archaeology that studies animal remains at archaeological sites)
Proboscideans - Another term for elephants and their close relatives
Pleistocene - The Pleistocene Epoch is the period of time starting 2.6 million years ago and ending 11,700 years ago. The reason it gets a fancy name is that it describes an ice age.
Fun fact: the word “Pleistocene” is a combination of two Greek words, pleistos (meaning “most”) and kainos (meaning “new” or “recent”). Therefore, the Pleistocene is literally the “most recent” ice age.
Paleolithic - The Paleolithic Period is marked by the development of stone tools approximately 3.3 million years ago and extends until the end of the Pleistocene (11,700 years ago). The term "Paleolithic” is often used interchangeably with “Stone Age” or “Early Stone Age”.
Neolithic - We haven’t encountered this term yet, but the Neolithic Age marks the end of the Stone Age/Paleolithic period with the introduction of farming and the domestication of animals. The Neolithic Age begins approximately 11,000 years ago.
Here’s a timeline to help visualize some of these dates in their historical context:
So, what does all of this mean?
In essence, this paper is going to examine the important role large herbivores played in the human diet over the last 2-3 million years.
Okay, with that as the background, let’s jump into the first section.
The introduction lays out the arguments of the paper. Here are the main points that stand out to me:
We know that human evolution has been heavily dependent upon animals for food as well as "materials for utensils, construction, clothing, and hunting gear”
The extinction of many large herbivores had a significant impact on the direction of human evolution
Current interpretations of human dependence on animals underappreciate the role that large game sources played in our evolution
This oversight resulted from assuming that faunal assemblages at archaeological sites accurately reflect human nutritional trophic preference. In other words, we’ve been assuming that the bones we find in ancient human campsites are a good representation of the types of animals humans mostly ate.
That last point appears to be the crux of the paper. Ben-Dor and Barkai contend that the modern understanding of human history fails to appreciate the impact that large herbivores (and their eventual absence) had on the evolution & development of the human species.
This isn’t just an argument over semantics. Getting the interpretation right has implications on our ability to make sense of numerous lines of evidence:
“A hypothesis regarding the reasons for the importance of acquiring large prey in the Palaeolithic can advance our ability to draw concrete adaptive predictions from identified changes in prey size composition in faunal assemblages. Testing and applying the hypothesis can lead to a better understanding of the role megaherbivores played in the cultural and biological history of humanity.” (pg. 3, emphases mine)
As we’ll see in the rest of the paper, Ben-Dor believes that a proper understanding of the significance of large herbivores can explain developments in the human species ranging from brain size to speech to the domestication of dogs and even agriculture.
12.2 The Importance of Megaherbivores in Paleolithic Subsistence
Ben-Dor goes on to list some of the published archaeozoological and paleontological evidence demonstrating humankind’s long history of hunting large prey.
Our earliest evidence of big-game hunting comes from Homo erectus nearly 2 million years ago. This early human species thrived on large prey, as is evidenced from archaeological sites ranging across Africa, the Levant, Europe, and Asia.
Ben-Dor also notes:
“Additional support for humans’ preference for large prey can be gained from the pattern of the extinction of large but not small animals in association with humans’ introduction to previously unoccupied regions.”
While there appears to be some controversy whether large-animal extinctions were a result of human hunting or climate change (or both), there is no question that human migration to islands (Australia, New Zealand, Hawaii, etc.) quickly & consistently resulted in the extinction of the island’s large animals.
Lastly, Ben-Dor points out that modern-day hunter-gatherer tribes like the Hadza of Tanzania also show a strong preference for large prey when it is available.
A Quick Note on Human Species
Above, we referenced an early human species called Homo erectus. In case you’re unfamiliar, there are several human species in the hominid lineage. Here’s a graphical representation of some of the stops along the way to modern humans (Homo sapiens):
There is a lot of debate about what the human “family tree” should look like, and I wouldn’t worry too much about remembering every detail. As new fossil evidence comes to light, the dates and relationships will change.
However, when talking about our own species, Homo sapiens, the most common names that you will hear & read about are usually:
Australopithecus afarensis (~4 million to 3 million years ago)
Homo habilis (~2.6 to 1.5 million years ago)
Homo erectus (~1.9 million years ago to possibly ~100,000 years ago)
Homo heidelbergensis (~600,000 to 200,00 years ago)
Homo sapiens (~300,000 years ago to the present day)
As I mentioned, these dates are approximations and subject to change, but they give you a rough sense of when each species lived.
Below is an artist’s reconstruction of what a few of these species may have looked like:
I hope that helps make this topic feel more “real”. When we’re talking about Homo erectus hunting big-game on the African savannah, we are talking about an intelligent, highly social species that looked quite similar to a modern-day human.
12.2.1 Why Humans Preferred to Acquire Large Prey
Ben-Dor cites four factors that made megaherbivores a primal target of human predation:
High relative biomass density of megaherbivores
Their tendency to not escape from predators
Higher net energetic return that is gained from their acquisition
Their relatively high fat content
Before we jump into the four factors, allow me a quick aside…
There is an interesting discussion on pages 4-5 that analyzes a paper by two researchers named Lupo and Schmitt (2016). The Lupo & Schmitt paper argues that large animals are actually ranked lowest in terms of net energetic return. However, Ben-Dor and Barkai demonstrate how relatively small changes in initial assumptions can significantly alter those calculations. They go on to provide evidence from an actual case study that flatly contradicts the Lupo and Schmitt hypothesis.
The discussion highlights an all-too-common problem, particularly in nutrition research: the failure to account for confounding variables. Nutritional epidemiology is infamous for drawing conclusions from insufficient or irrelevant data. We always need to be careful about the initial assumptions that we bring to a problem because they can (and will) influence the conclusions we draw.
Okay, back to the paper…
Let’s briefly look at each of the four factors that made large prey the preferred source of human nutrition.
Factor #1: Large Prey Have High Relative Biomass Density
High relative biomass density is another way of saying that large herbivores represent the majority of the physical mass of animals in a given environment. For example, if you could gather up all the elephants, hippos, rhinos, deer, squirrels, rabbits, and other animals and weigh them together, then the large herbivores would represent a disproportionately high % of the total mass.
In most environments, large herbivores represent a majority of the total available calories from animal sources. Therefore, since the majority of the calories in most environments are concentrated in a small niche, it makes sense to take advantage of that niche.
There are a couple more terms used in this section that may be unfamiliar to readers:
Quaternary Period and Holocene epoch - The Quaternary period is the current and most recent of the three periods of the Cenozoic Era. The Quaternary is split into two epochs: the Pleistocene and the Holocene. We already learned about the Pleistocene (~2.6 million years ago to 11,700 years ago). The Holocene began at the end of the Pleistocene and includes the present day.
Here’s a great graphic that demonstrates how epochs, periods, and eras relate to one another:
Factor #2: Large Prey Tend Not to Escape From Predators
Large herbivores are generally slow relative to predators, and escape is usually not their go-to form of protection. Instead, large herbivores tend to cluster together for protection, or else they charge would-be predators.
Ben-Dor and Barkai point out that “The smaller and faster the animal is, the more complex the technology that is used in its acquisition (Churchill, 1993)” (pg 7). In human evolution, the technological demand looked something like this:
Thrusting spears for non-escaping megaherbivores
Throwing spears (with stone tips) for medium size-medium weight animals
Bow and arrow for smaller and faster herbivores
We’ll come back to this point later since it had major implications in the trajectory of human evolution.
Factor #3: Large Prey Provide Higher Energetic Return
Larger animals provide more absolute nutritional calories than smaller animals. Additionally, larger animals also have a proportionally higher fat content than smaller animals. This means, on average, that a single 1,000 kg animal is worth more - in terms of calories - than five 200 kg animals. Check out how fat % scales with weight:
There is a well-known behavioral model called Optimal Foraging Theory that helps predict how an animal will behave in its search for food. In short, animals are constantly balancing two competing desires:
The desire to consume more energy (i.e. more nutrients/calories)
The desire to expend less energy (i.e. move/work less)
Optimal foraging theory helps us understand how an animal will balance those two desires based on its environment.
In the case of humans, they had a wide range of available food sources to choose from: small animals, large animals, fruits, tubers, nuts, seeds, and more. However, when viewing the choices through the lens of Net Calories Per Hour, the choice becomes obvious: large animals are the clear winners.
By comparison, Ben-Dor cites calorie data from Robert Kelly’s book The Lifeways of Hunter-Gatherers for several popular plant foods:
Seeds: 191–13,437 kcal/hr
Berries: 250–4,018 kcal/ hr
Tubers: 267– 6,252 kcal/hr
Ben-Dor’s point is not that humans never ate plant foods. There were certainly times throughout evolutionary history where humans needed to fall back on local vegetal sources for nutrients & energy. But it’s also clear that large animals were always the #1 preferred source whenever they were available.
Factor #4: Large Prey Have Relatively High Fat Content
We already discussed how larger animals have a proportionally higher % of fat mass compared to smaller animals. This little fact is important because of how protein metabolism works in the human body.
When proteins are metabolized, the nitrogen-containing portion is converted into ammonia. Left unchecked, ammonia is toxic to humans, so it is quickly converted by the liver into urea. Urea is then passed to the kidneys for filtering and is eventually excreted in the urine. This process is known as the Urea Cycle.
Humans can metabolize up to 35-50% of their calories from protein without a problem, but any higher and the liver & kidneys become a bottleneck in removing ammonia & urea. Therefore, humans need to get the rest of their calories (50-65%) either from fat or carbohydrate.
This is why large herbivores were so important to the human diet. Large herbivores naturally contain the majority of their calories as fat, so humans don’t have to worry about over-consuming protein. In essence, large herbivores are ready-made “meals on wheels” for humans.
Pass the mammoth steak, please.
12.3 A Method To Correct the Under-Representation of Large Animals in Palaeolithic Archaeological Assemblages
If you want to learn why previous analyses of faunal assemblages have underestimated the contribution of large herbivores in the human diet, then read this section in the paper.
The main argument can be summarized as follows:
Large animals have large bones
Large bones are heavy
Therefore, large animals (more specifically, their bones) often weren’t transported back to camp, thereby skewing the representation of animals in a given faunal assemblage.
The argument is supported by an interesting series of case studies of an African hunter-gatherer group called the Hadza.
Researchers compared the faunal assemblage of several sites with known records of the animals hunted & consumed by the Hadza. The comparison demonstrated that large animals were significantly underrepresented.
For example, one of the samples showed that giraffes only made up 7% of the faunal assemblage, yet cross-comparison indicated that those same giraffes actually constituted 57% of the total weight of the assemblage. That’s a big difference!
I found this section an illustrative example of how easy it is for any of us to be fooled by “the evidence”. I have no reason to doubt that the archaeologists who devised the traditional assemblage formula were doing the best they could with the information they had. I’m sure their formulas were based on excellent laboratory observations.
And yet, they failed to adequately account for the fact that, in the real world, humans don’t want to lug around heavy-a** bones if they don’t have to. Go figure.
I guess the Russians had it right after all: “Trust, but verify.”
12.3.1 Cumulative Presentation of the Biomass Abundance Index
Sections 12.3.1-12.4.3 demonstrate how an understanding of megaherbivore behavioral patterns - and their relation to humans - provide a unique analytical toolset for examining human behavior.
One of the examples that stood out to me was a comparison of Neanderthals versus anatomically modern humans (AMH) in southern France. It appears that Neanderthals obtained about 30% of their diet from non-escaping animals (i.e. megaherbivores), whereas AMH obtained about 15% of their diet from the same. Additionally, Neanderthals obtained over 90% of their calories from high-fat content animals (>200 kg), whereas AMH only obtained 60%.
As Ben-Dor notes:
These differences can shed light on possible physiological and cultural adaptations that allowed modern humans to succeed in handling both these handicaps. It can be hypothesized that lighter bodyweight and advanced agility allowed AMH to acquire smaller escaping animals at reduced locomotion costs (Steudel-Numbers and Tilkens, 2004). Use of projectile hunting tools, which are used mainly on smaller prey, is also sometimes mentioned as a differentiating capability.
It’s interesting to consider that the anatomical structure of modern humans (increased shoulder mobility, improved locomotive ability, lighter bodyweight) may have been selected due to the declining presence of megaherbivores in the environment.
Humans evolved as hypercarnivores, meaning we consumed more than 70% of our calories from animal sources. The extinction of megaherbivores - likely due to human over-hunting - didn’t suddenly change that fact. Humans had to adapt to hunting smaller animals in order to continue getting the fat, protein, vitamins, and minerals that built our species.
In other words, humans didn’t shift to hunting smaller animals because they wanted to. Bow & arrow technology and the domestication of dogs was to help humans cope with hunting smaller, faster, and (most critically) leaner game.
As Ben-Dor notes in another of his papers, man is a “fat hunter”. If fat calories are removed from the environment - like with the extinction of large herbivores - then humans will go to extraordinary lengths to replace it with fat from smaller animals. At some point, however, even that becomes insufficient, which is why we see an increased reliance on plant foods near the end of the Pleistocene and eventually the domestication of plants in the Neolithic. You gotta get your calories from somewhere.
12.5-12.5.1 and 12.6: Discussion, Underrepresentation of Proboscideans, and Conclusions
The paper finishes with a summary of the main points covered and presents several ideas for future lines of research. I want to highlight two points before we wrap up this article:
Underrecognition of the true relative abundance of large prey animals in archaeological sites may blind us to the importance of large prey animals in general, and to specific trends in large prey prevalence that could drive the hypothesized adaptations. (pg. 17)
The question that we tried to answer here was how we could determine the relative importance of large and very large animals in archaeological assemblages. The answer to this question, in general and in particular situations, may have critical implications for understanding human behavior and evolution. (pg. 18)
In my mind, the reason this paper is so important is that highlights the mismatch between our perceptions of the past and the reality of the past. It is easy to assume that the past was essentially the same as today, but that assumption can (and does) lead to erroneous conclusions.
I’m reminded of a nutritional epidemiology paper from the late 1940s/early 1950s that looked at the diet of Okinawans in Japan [Note: if someone can find this paper, please tag me in the comments - it’s been a long time since I’ve read it and my Google skills are failing me]. Specifically, the paper looked at the diets of centenarians in an effort to understand how nutritional habits may have contributed to their extended lifespans. If I recall correctly, the paper concluded that Okinawan centenarians ate a diet very high in carbohydrates (mostly sweet potato) and very low in animal products. Therefore, the authors concluded that must be a contributing factor to the Okinawans’ long lifespans.
Can you see the problem with that conclusion?
The paper failed to account for a little event that occurred in Japan several years earlier: World War II. The war efforts had a significant impact on food supply chains, particularly animal products. I’ve read several accounts that the pig population in Japan was around 100,000-200,000 head prior to the war but dropped as low as 800 head afterward.
Is it any surprise that Okinawan centenarians weren’t eating much pork in the late 1940s/early 1950s?
Ben-Dor’s paper is making the same point regarding our evolutionary past. It is easy today to look at the few remaining hunter-gatherer groups around the world and assume that their lifestyle is an accurate reflection of our ancestral past. However, just as WWII had a significant impact on the dietary habits of post-war Japanese citizens, so too did the extinction of large herbivores have a significant impact on the dietary habits of ancestral humans.
If we fail to account for the role that large herbivores played in human evolution, then we are at risk of drawing false conclusions about the dietary patterns that shaped our development as a species.
Alright, that wraps up our review of the first paper in Ben-Dor’s four-part series.
In the next article, we will look at additional evidence for the primacy of large herbivores in human evolution. We’ll also examine the real-life implications as seen through the lens of several modern-day hunter-gatherer groups, including the Hadza and the San Ju/’hoansi (!Kung).
See you in Part 2!