Has meat really played the starring role in the evolution of the human diet? It is true that early hominins craved meat but it turns out that what our distant ancestors desired and what they actually acquired were not the same.
Observation of present-day hunter-gatherer societies reveals that they have negligible success as hunters, even with bows and arrows in their arsenal. For many of the hundreds of thousands of years that spanned human development, efficient weapons did not even exist. A successful kill to provide meat might happen only a couple of times a month. So how did they survive? (1)
The gathering of food to satisfy the energy needs of early societies was fulfilled by the women, with some help from children, who spent their days foraging for “fallback foods”. Fruits, grasses, tubers and nuts were there for the taking, rooted into the ground and not prone to running away. Even today, plants make up at least 70% of the food for the hunter-gatherer societies that still exist. The Hadza and Kung bushmen in Africa depend on tubers and nuts; the Ada and Baka Pygmies of the Congo River Basin on yams; the Tsimane and Yanomami Indians of the Amazon on plantains and manioc; and the Australian Aboriginals on nut grass and water chestnuts. (1)
Considerable evidence concerning the plant-eating habits of our predecessors is gradually emerging. Starch granules from archaic plants found in caves once inhabited by ancient people in Africa and Spain, traces of tubers and grains on the fossilized teeth of Neanderthals and stone grinding tools tell the story of the diet of early humans (12,13). It appears that plants have been the main food source of most of humankind for least 100,000 years, long before agriculture and the domestication of animals began around 12,000 years ago.
Other new research, published in October 2024 by the University of Buffalo, found evidence of prehistoric humans depending on plant-sourced foods starting even earlier than previously thought. In this analysis, the researchers honed-in on an enzyme, amylase, that is required to metabolize starchy carbohydrates like yams and other tubers, nuts, grasses, grains, potatoes, beans and corn and turn them into calories. Humans are unusual in that we have many more than one copy of the gene responsible for the production of amylase in our DNA. (2,3)
If you hold a starchy food like bread in your mouth for a minute or two, you can experience the result of amylase working when you begin to taste sweetness. The amylase enzyme (AMY) breaks down complex carbohydrates into maltose, a sweet-tasting sugar that is made up of two glucose molecules linked together. Amylase is present both in our mouths (AMY1) and in the pancreas (AMY2). AMY1 gives a head start to the tough task of breaking down carbohydrates by beginning their digestion as soon as they enter the mouth. AMY2 is secreted from the pancreas into the small intestine where it interacts with food carbohydrates resulting in their digestion and absorption. Researchers of this study concluded that, because early human populations were eating a diet high in starches, they evolved to be able to create numerous copies of the amylase gene in their DNA. (2)
Scientists had been looking for the point in human history when the amylase gene began to occur in multiple copies. However, their search was hampered by the placement of these genes in a part of the genome that was difficult to sequence. Traditional sequencing methods struggled to accurately distinguish between the near-identical sequences of the genes. This new study used advanced techniques of genome mapping and sequencing and was able to sequence 98 modern-day DNA samples and 68 ancient DNA samples. Researchers then tracked how the number of amylase genes changed over time. They found that, long before farming and growing crops began, hunter-gatherers had between four and nine copies of the gene for amylase in their cells. (2)
This investigation also found AMY1 gene duplications that occurred in Neanderthals and Denisovans, both archaic predecessors of modern humans. Neanderthals lived in Europe and Western Asia from around 400,000 years ago until they became extinct approximately 40,000 years ago. Denisovans lived from about 285,000 to 25,000 years ago. The existence of many gene copies in these species suggest that the AMY1 gene may have first duplicated more than 800,000 years ago, well before humans split from Neanderthals and much further back than previously thought. (2)
Another pertinent study was published in September 2024 from UC Berkeley. It confirmed that the number of copies of the amylase gene is higher in populations with high starch intake compared with those eating a diet containing more animal-sourced food. Scientists have long suspected that the human ability to digest starch might have been further augmented around 12,000 years ago as our forebears began to delve into agriculture, domesticating plants and growing their own foodstuffs. This study did indeed demonstrate that, as the grain content of their diet rose with the farming of plant foods, their genome gradually changed too, with amylase gene copies rising up to eleven, offering more efficient digestion of their food and boosting the amount of energy they could capture from the starchy foods they were eating. (4)
What does all this mean for us in the present day? For one thing, it debunks the theory that supports the carnivore diet – that our human ancestors relied heavily on animal-sourced foods and therefore that our bodies evolved to eat animals (5). On the contrary, the discovery of multiple copies of amylase genes in our earliest forbears indicates that they were actually sustaining themselves by eating mostly plants.
So, we did not develop as carnivores. But are we herbivores, meant to eat a plant-predominant diet? An interesting paper published in 2000 may help to shed some light on these questions through the examination of the characterization of animals into carnivores, herbivores and omnivores and their susceptibility to atherosclerosis. (6)
Atherosclerosis is the build up of fats, cholesterol, and other substances in and on the walls of arteries causing them to narrow and become thick and stiff and leading to the development of chronic diseases like (6,7)…
- Coronary artery disease -disease of the arteries close to the heart that can cause chest pain, a heart attack or heart failure
- Carotid artery disease – disease of the arteries close to the brain which can trigger a TIA (transient ischemic attack) or a stroke
- Peripheral artery disease – disease of the arteries in the arms and/or legs which can cause muscle pain and interfere with the performance of muscles. For example, peripheral artery disease in the legs results in pain when walking and reduces the ability to walk any distance.
- Aneurysms -bulges in an artery wall which can burst and cause life-threatening bleeding
- Chronic kidney disease -narrowing of the arteries leading to the kidneys which interfere with their essential task of removing fluids and waste products from the body
Consider the following information (6,8).
- We now know that atherosclerosis does not occur in every animal but generally only in humans and in non-human herbivores who have been lab-fed a diet high in cholesterol and/or saturated fat, similar to what modern humans eat
- It is not possible to produce atherosclerotic plaques experimentally in carnivores. Carnivores (animals such as dogs, wolves, cats, lions, and cheetahs) that eat mostly animal-sourced foods can gorge themselves on fat and cholesterol but they never develop atherosclerosis.
- Bears are omnivores. They don’t develop atherosclerosis in spite of having high cholesterol blood levels during their hibernation (9).
- Atherosclerosis is only very rarely a result of genetics and it is not simply a degenerative disease of aging.
- The following factors increase the likelihood of developing atherosclerosis – high total and LDL-cholesterol blood levels, high blood pressure, diabetes, obesity, low-HDL cholesterol levels, smoking and inactivity. Most of these risk factors are indirect in that they support and accelerate the growth of atherosclerotic plaques but do not produce them on their own. The only direct risk factor for atherosclerosis is the level of cholesterol in the blood. The development of atherosclerosis requires high cholesterol blood levels over an extended period of time. As a matter of fact, adding up a person’s levels of LDL-C (low density lipoprotein cholesterol) over time can capture both the magnitude and duration of exposure to cholesterol and result in a fairly accurate estimation of the absolute risk of having an acute cardiovascular event at any point in time (10).
- Atherosclerotic plaques contain cholesterol
- Humans have many of the characteristics of herbivores. For example,
Carnivores have sharp claws; herbivores have hoofs or hands.
Carnivores have a short intestinal tract (3 times their body length); herbivores have a very long intestinal tract (12 times their body length.)
Carnivores have sharp teeth for tearing; herbivores have mostly flat teeth for grinding.
Carnivores have very large mouths relative to the size of their head and their jaw is a hinge joint that lies on the same plane as the teeth making it the very strong and stable joint necessary for catching, killing and tearing apart their prey; herbivores have a small mouth relative to their head and their jaw is attached above the plane of the teeth allowing the side-to-side and forward-to-backward movements necessary for grinding fibrous plant material
Carnivores cool off by panting; herbivores cool off by sweating.
Carnivores lap fluids, herbivores sip fluids.
Carnivores produce their own vitamin C; herbivores get vitamin C from the plants in their diet.
From this we can observe that human beings show a lot of characteristics typical of herbivores. Despite this however, we can’t presume that humans are herbivores. We know that though early humans ate a lot of plants, they also ate food from animal sources when they could which would class them as omnivores. And in reality, it’s more likely that we evolved as omnivores, “opportunistic feeders” who sustained themselves on whatever they could find to eat. Our forebears were able to survive the long evolutionary journey that created modern humans because they were able to obtain the calories they needed to live from a wide range of possible foods, both animal-sourced and plant-sourced. (11)
When it comes right down to it though, it doesn’t matter whether we label ourselves as omnivores, herbivores or carnivores. In today’s world of food abundance we have the luxury of choosing to eat whatever we want, whenever we want, whether their source is animal or plant. But we now also have the knowledge to select the foods that are known to optimize the health of our bodies.
The fact that humans possess multiple copies of the genes that code for the enzyme necessary for the metabolism of plants into needed energy suggests that we humans, as we evolved from the first hominin, Australopithecus, all the way up to modern Homo sapiens, became genetically optimized to eat carbohydrates from plants. Our modern problem of developing atherosclerosis, along with its many serious downstream diseases, through the consumption of too many animal-sourced foods indicates that foods sourced from plants are the best choice for the health of our cardiovascular system. Add to this the mountain of existing evidence revealing that plant-predominant diets promote excellent health and significantly lower the risk of not only cardiovascular diseases, but of many other chronic diseases that now plague humankind.(5)
We have choices. We can be an herbivore, eating only plants, or a carnivore, eating mostly animals, or an omnivore eating both plants and animals. But keep in mind that the road to optimal health is best travelled by choosing to eat mostly plant-source foods.
SOURCES:
1 https://www.nationalgeographic.com/foodfeatures/evolution-of-diet/?topicId=article.20200729093231781
2 Yılmaz, F. et al. Reconstruction of the human amylase locus reveals ancient duplications seeding modern-day variation. Science. Oct 17, 2024; DOI:10.1126/science.adn0609.
3 https://www.smithsonianmag.com/smart-news/cant-get-enough-carbs-that-craving-might-have-started-more-than-800000-years-ago-180985297/
4 Bolognini, D., Halgren, A., Lou, R.N. et al. Recurrent evolution and selection shape structural diversity at the amylase locus. Nature 634.2024; 617–625. https://doi.org/10.1038/s41586-024-07911-1.
5 https://nutritionstudies.org/the-carnivore-diet-what-does-the-evidence-say/
6 Roberts, W.C. Twenty questions on atherosclerosis. Proc (Bayl Univ Med Cent). 2000 Apr;13(2):139-143. Doi: 10.1080/08998280.2000.11927657. PMID: 16389367; PMCID: PMC1312295.
8 Gisterå, A., Ketelhuth, D.F.J., Malin, S.G., Hansson, G.K. Review Article: Animal Models of Atherosclerosis–Supportive Notes and Tricks of the Trade. Circulation Research. June 9, 2022; 130(12). https://doi.org/10.1161/CIRCRESAHA.122.320263
9 https://www.asbmb.org/asbmb-today/science/062221/cholesterol-lessons-from-bears
10 Ference, B.A., Braunwald, E. & Catapano, A.L. The LDL cumulative exposure hypothesis: evidence and practical applications. Nat Rev Cardiol 21. 2024;701–716. https://doi.org/10.1038/s41569-024-01039-5
11 Bradford, A. Omnivores: Facts About Flexible Eaters. Livescience.com; Live Science. January 26, 2016. https://www.livescience.com/53483-omnivores.html#:~:text=The%20food%20is%20softened%20in,that%20either%20carnivores%20or%20herbivores.
12 https://www.sciencenews.org/article/cave-debris-may-be-oldest-known-example-people-N eating-starch
13 https://www.york.ac.uk/news-and-events/features/el-sidron/
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My name is Debra Harley (BScPhm) and I welcome you to my retirement project, this website. Over the course of a life many lessons are learned, altering deeply-rooted ideas and creating new passions.
