Updated: Mar 15
About 65 million years ago the dominant species on Earth, the dinosaurs, were wiped out due to some sort of catastrophic event. It could have been a meteor hitting the Earth, or many volcanoes erupting at once. Regardless, the environment changed too rapidly for those large animals to survive. But there were some animals that did survive, like the small mammals that were present at the time. When these events took place the average size of a mammal was about 100 grams, no bigger than a mouse.
Since the dinosaurs were now gone, it paved the way for mammals. From 65 million years ago until about 2.5 million years ago the average size of mammals grew significantly from that 100 grams to 550 kilograms. Around this same time, 2.5 million years ago, we see the first of the genus Homo rise out of the archeological evidence. Paleoanthropologists feel that one reason we see the first Homo species appear around this time was the fact that some individuals or groups from the prior Australopithecus species began eating meat. Curiously, at this time is when we also started to see the die-off of the large mammals that evolved, especially anywhere a Homo species showed up too. It was very clear that our early Homo ancestors were killing and eating these large mammals. (1)
Because of this, the average size of mammals today has gone down to about 10 kilograms. This behavior of eating large mammals played a large part in driving the evolution of the genus Homo. We went from Homo habilis to Homo erectus to Homo heidelbergensis to Homo neanderthalensis to us modern-day Home sapiens. This eating of animals caused changes such as an explosion of brain size, (2) an increase in stature, (3) and a change in our digestion from a focus on fermentation to direct absorption. We humans did not evolve to eat animals, we evolved to what we are today because we ate animals for the last 2.5 million years. By testing the stable isotopes within bones of Neanderthals and early modern humans and comparing it with other known carnivores at the time, it seems that our human ancestors were largely carnivorous. (4,5)
However, we sort of did ourselves in. It took 63 million years for mammals to reach an average size of 550 kilograms and then because of the rate at which they were killed for food by our human ancestors it only took 2.5 million years for them to go to a 10-kilogram average size. As much as eating these animals was leading to humans becoming a dominant species, we were also killing off the food supply that got us there. I liken this to the same thing we are seeing today. Humans are polluting the Earth in many ways and it is threatening the health of the environment in which we live. But this is not a new trend, the widespread killing of large mammals starting 2.5 million years ago shows us that we humans have been doing ourselves in since we became human.
That being said, the massive growth of our brains made us pretty smart. When the population of humans grew and the population of the food supply helping us create that growth dwindled, humans were able to find a different source of calories. About 10-12 thousand years ago we see the first evidence of plant agriculture. (6) Today plant agriculture is the source of most of our calories and nobody really thinks twice about it.
However, archeological evidence of the first farmers showed that they struggled with their health. It has been shown that while the switch to farming lead to an increase in population it also resulted in a decline in health as humans suffered from infections, dental issues, weak bone structure, and malnourishment. (7) It has even been shown that our brains have gotten smaller over the last 10,000 years. (8)
In my opinion, this was the very beginnings of the chronic disease epidemic that we have today. The switch to agriculture forcefully shifted, not only our diet, but our entire way of life away from the way of life that literally made our bodies and physiology the way they are. As we track through history, we see that ancient civilizations also struggled with health.
It is often said that heart disease is a new phenomenon of the last 150 years or so and it is often incorrectly explained by the fact that humans are eating more meat now. Clearly, based on the research showing that humans used to be high level carnivores cited above, that is not true. Humans have been eating meat and saturated fat for millions of years. The health issues with eating a plant agriculture-based diet are many. This is especially evident in Ancient Egypt. Egyptian mummies have been examined and it has been shown that 34% of them had evidence of atherosclerosis. (9) Egyptians also describe heart attacks in their ancient text Ebers Papyrus saying:
“And if though examinst a man for illness in his cardia, and he has pains in his arm, in his breast, and in side of his cardia, and it is said of him: It is illness, then thou shalt say thereof: It is due to something entering the mouth it is death that threatens him.”
It is well known that the ancient Egyptians were a farming culture that subsisted on wheat, emmer, and barley. Much of their artwork shows images and statues of them harvesting and grinding wheat. Yet, their heart disease was likely not an epidemic like we have today. There was something keeping the negative health effects of a society relying on agriculture from developing into an epidemic, infection.
With agriculture came higher rates of infection. This happened because humans were living very close together and often times in very close proximity to livestock. Before this time, it would have been advantagous for a bacteria to infect a host only to the extent that it could benefit from the host and live in it, but not to the extent that it killed the host. However, when many hosts, human or animal, were in close proximity to each other, then the bacteria could evolve to infect a host to the point of killing the host because it could just move on to the next host. This is why infections often make us sneeze or cough, the bacteria wants to spread to another host. The concentration of people and animals into one area allowed for the evolution of bacteria and the increase of death by infection.
This increase rate of infection was keeping the negative health effects of an agriculturally based society from becoming an epidemic. This was because many people died before those negative health effects of a plant agriculture-based diet could show up. To use an analogy to illustrate, this would be like a house where the roof is leaking, the foundation is crumbling, and the pipes in the walls are rusting. These are the negative health impacts that the house is having due to relying on plant agriculture. However, before those issues can become life-threatening health problems for the house, it burns down. The fire that burns it down is the infection. So, in a way the epidemic of chronic disease we have today may seem recent, but it has been there since humans switched to plant agriculture based societies long ago.
In the 1900’s we started to figure out that sanitation and hygiene in our cities was important for preventing infection. Antibiotics also came on the scene in 1928. Suddenly infection was no longer the killer it had been, and average lifespan went from the mid-forties in the early 20th century to the mid-seventies today. (10) This opened the door for the negative health effects of a diet based on the products of plant agriculture to finally become the dominant health concern among humans. And that is exactly what we have seen since the decrease in infections, a massive jump in cancer, diabetes, and heart disease.
This perceived increase in chronic disease, that really had always been there, has been wrongfully blamed on the eating of animal products. But as I am sure you can see, that makes no sense. It was the eating of animals that made us humans who we are today. It is what led us to the development of the characteristics that we see in modern humans, the characteristics that gave us the evolutionary advantage to become as successful as we have become. So successful, in fact, that we were even able to find a way to survive through plant farming, though not thrive, when we killed off the food source we had relied on to make us human, large mammals. It was only when we strayed from our evolved species appropriate diet that our health issues started. Human ingenuity has kept us going, but the rise in chronic disease is growing. Blaming that rise on the original human diet of meat and saturated fat makes no sense.
Add to this the fact that modern day research has shown that people with higher meat and fat intake live longer and the true picture starts to come together. (11,12,13,14) To achieve the highest level of health and protect yourself from diseases like heart disease, an animal-based diet is the way to go.
Stay healthy out there!
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