Our earliest tool-making ancestors survived on a mostly meat-based diet until about 80,000 years ago when large animals died out and they were forced to eat more vegetables, according to the findings of a new study.
Researchers from Tel Aviv University were able to reconstruct the nutrition of stone age humans by examining 400 scientific papers from different disciplines.
These papers, the majority of which focused on human biology, examined the genetics, metabolism, physiology and morphology of our ancient ancestors.
They discovered that humans were ‘hypercarnivores’, an apex predator with meat making up 70% of their diet for about two million years, and it was only the extinction of larger animals that changed their diets.
The decline of animal food sources toward the end of the stone age, between 80,000 and 40,000 years ago, led humans to eat more vegetables and less meat.
This change continued until finally our earliest ancestors had no choice but to domesticate both plants and animals – and became farmers, the Israeli team said.
Our earliest tool making ancestors survived on a mostly meat-based diet until about 80,000 years ago when large animals died out and they were forced to eat more vegetables, according to the findings of a new study. Stock image
The decline of animal food sources toward the end of the stone age, between 80,000 and 40,000 years ago, led humans to eat more vegetables and less meat
Dr Miki Ben-Dor and colleagues set out to investigate whether stone-age humans were specialised carnivores or were they generalist omnivores.
‘So far, attempts to reconstruct the diet of stone-age humans were mostly based on comparisons to 20th century hunter-gatherer societies,’ explains Dr Ben-Dor.
The team say this was a futile comparison, as two million years ago hunter-gatherers had access to large megafauna including elephants.
‘The ecosystem has changed, and conditions cannot be compared,’ Ben-Dor said, so they ‘decided to use other methods to reconstruct the diet of stone-age humans.’
This allowed them to examine the memory preserved in our own bodies, our metabolism, genetics and physical build.
‘Human behaviour changes rapidly, but evolution is slow. The body remembers.’
A prominent example of this slow evolutionary change is seen in the acidity of the human stomach, Ben-Dor explained, adding that the acidity in our stomach is high when compared to omnivores or even other predators.
‘Producing and maintaining strong acidity require large amounts of energy, and its existence is evidence for consuming animal products,’ he said.
Strong acidity provides protection from harmful bacteria found in meat, and prehistoric humans, hunting large animals whose meat sufficed for days or even weeks, often consumed old meat containing large quantities of bacteria.
Another indication of being predators is the structure of the fat cells in our bodies, the team said, as fat is stored in a relatively small number of fat cells in omnivores.
While in predators, including humans, it’s the other way around, with humans having a much larger number of smaller fat cells.
‘Significant evidence for the evolution of humans as predators has also been found in our genome,’ said Ben-Dor.
‘For example, geneticists have concluded that areas of the human genome were closed off to enable a fat-rich diet, while in chimpanzees, areas of the genome were opened to enable a sugar-rich diet.’
Evidence from human biology was supplemented by archaeological evidence, allowing the Israeli team to pain a broader picture of stone age diets.
For instance, research on stable isotopes in the bones of prehistoric humans, as well as hunting practices unique to humans, show that humans specialised in hunting large and medium-sized animals with high fat content.
The team then compared humans to large social predators of today, who hunt large animals and obtain 70 per cent of their energy from animal sources.
This reinforced the conclusion that humans specialised in hunting large animals and were in fact ‘hypercarnivores’ – that is a creature with at least 70% of their diet made up of meat or animal products.
Evidence from human biology was supplemented by archaeological evidence, allowing the Israeli team to pain a broader picture of stone age diets. Stock image
This change continued until finally our earliest ancestors had no choice but to domesticate both plants and animals – and became farmers, the Israeli team said
‘Hunting large animals is not an afternoon hobby,’ says Ben-Dor. ‘It requires a great deal of knowledge, and lions and hyenas attain these abilities after long years of learning.’
‘Clearly, the remains of large animals found in countless archaeological sites are the result of humans’ high expertise as hunters of large animals,’ he added.
Many researchers who study the extinction of the large animals agree that hunting by humans played a major role in this extinction – and there is no better proof of humans’ specialisation in hunting large animals.
‘Most probably, like in current-day predators, hunting itself was a focal human activity throughout most of human evolution,’ Ben-Dor said.
‘Other archaeological evidence – like the fact that specialised tools for obtaining and processing vegetable foods only appeared in the later stages of human evolution – also supports the centrality of large animals in the human diet.’
The team spent the best part of a decade on the project to explore ancient human diets and better understand human evolution.
It allowed them to propose a paradigm shift in the understanding of how our species came to be the most dominant predator on planet Earth.
Before this it was largely thought that humans owed their evolution and survival to their dietary flexibility, combining hunting with vegetables and foraging.
However, the new study reveals hat the true picture is one of humans evolving mostly as predators of large animals.
‘Archaeological evidence does not overlook the fact that stone-age humans also consumed plants,’ adds Dr. Ben-Dor.
‘But according to the findings of this study plants only became a major component of the human diet toward the end of the era.’
The team determined that the gradual increase in plant consumption happened around 85,000 years ago in Africa and 40,000 years ago in Europe and Asia.
They used genetic changes in humans and the appearance of unique stone tools for processing plants to make this conclusion.
This rise was accompanied by an increase in the local uniqueness of the stone tool culture, which is similar to the diversity of material cultures in 20th-century hunter-gatherer societies.
In contrast, during the two million years when, according to the researchers, humans were apex predators, long periods of similarity and continuity were observed in stone tools, regardless of local ecological conditions.
They discovered that humans were an apex predator for about two million years and it was only the extinction of larger animals that changed their diets. Stock image
‘Our study addresses a very great current controversy – both scientific and non-scientific,’ said professor Ran Barkai.
‘For many people today, the Paleolithic diet is a critical issue, not only with regard to the past, but also concerning the present and future.
‘It is hard to convince a devout vegetarian that his/her ancestors were not vegetarians, and people tend to confuse personal beliefs with scientific reality.
‘As Darwin discovered, the adaptation of species to obtaining and digesting their food is the main source of evolutionary changes, and thus the claim that humans were apex predators throughout most of their development may provide a broad basis for fundamental insights on the biological and cultural evolution of humans.’
The findings have been published in the journal American Journal of Physical Anthropology.
WHAT DO WE KNOW ABOUT THE HISTORY OF THE STONE AGE?
The stone age is a period in human prehistory distinguished by the original development of stone tools that covers more than 95 per cent of human technological prehistory.
It begins with the earliest known use of stone tools by hominins, ancient ancestors to humans, during the Old Stone Age – beginning around 3.3 million years ago.
Between roughly 400,000 and 200,000 years ago, the pace of innovation in stone technology began to accelerate very slightly, a period known as the Middle Stone Age.
By the beginning of this time, handaxes were made with exquisite craftsmanship. This eventually gave way to smaller, more diverse toolkits, with an emphasis on flake tools rather than larger core tools.
The stone age is a period in human prehistory distinguished by the original development of stone tools that covers more than 95 per cent of human technological prehistory. This image shows neolithic jadeitite axes from the Museum of Toulouse
These toolkits were established by at least 285,000 years in some parts of Africa, and by 250,000 to 200,000 years in Europe and parts of western Asia. These toolkits last until at least 50,000 to 28,000 years ago.
During the Later Stone Age the pace of innovations rose and the level of craftsmanship increased.
Groups of Homo sapiens experimented with diverse raw materials, including bone, ivory, and antler, as well as stone.
The period, between 50,000 and 39,000 years ago, is also associated with the advent of modern human behaviour in Africa.
Different groups sought their own distinct cultural identity and adopted their own ways of making things.
Later Stone Age peoples and their technologies spread out of Africa over the next several thousand years.