Extinction of Prey drove evolutionary changes in prehistoric humans

A new study from the Department of Archaeology at Tel Aviv University found that the extinction of large prey, upon which human nutrition had been based, compelled prehistoric humans to develop improved weapons for hunting small prey, thereby driving evolutionary adaptations. The study reviews the evolution of hunting weapons from wooden-tipped and stone-tipped spears, all the way to the sophisticated bow and arrow of a later era, correlating it with changes in prey size and human culture and physiology.

The researchers explain: “This study was designed to examine a broader unifying hypothesis, which we proposed in a previous paper published in 2021. The hypothesis explains the cultural and physiological evolution of prehistoric humans – including increased cognitive abilities – as an adaptational response to the need to hunt progressively smaller and quicker prey. So far such a unified hypothesis was lacking in professional literature, with the prevailing hypothesis maintaining that the changes in hunting weapons were a reflection of an essentially unexplained cognitive improvement.”

The study was led by Dr. Miki Ben-Dor and Prof. Ran Barkai from the Department of Archaeology at Tel Aviv University. The paper was published in Quaternary.

Dr. Ben-Dor: “In the present study we analyzed findings from nine prehistoric sites – in South Africa, East Africa, Spain, and France, inhabited during the transition from the Lower to the Middle Stone Age (Paleolithic), about 300,000 years ago, when Neanderthals and Homo Sapiens first emerged. In early archaeological sites of this kind, we find mostly animal bones and stone tools used to hunt and process prey. The bones reflect the relative quantities of different species hunted by humans, such as elephants, fallow deer, etc. In this study we looked for a correlation between the advent of stone-tipped spears, and the progressive decline in prey size. Specifically, we examined the emergence of a sophisticated stone-knapping method known as the Levallois technique, which is especially indicative of cognitive development: unlike earlier knapping methods, here the craftsman first prepares a core of good-quality stone, then cuts a pointed item off with one stroke – a process that requires him/her to imagine the final outcome in advance. We found that in all cases, at all sites, stone tips made with the Levallois technology appeared simultaneously with a relative decrease in the quantity of bones of large prey. ”

Reviewing the evolution of prehistoric hunting, the researchers explain that “humans began to make stone tools about 3 million years ago, and started to hunt about 2 million years ago, with hunting weapons evolving constantly throughout prehistoric times. Homo Erectus, the ancestor of all later types of humans, used a wooden spear, probably thrusting it into large prey from up close. Homo Sapiens and Neanderthals, emerging about 300,000 years ago, upgraded their spears by adding stone tips, which they produced with the more sophisticated Levallois technique. These stone-tipped spears were apparently used for both thrusting and hurling. About 50,000 years ago more complex hunting systems like the bow and arrow and spear thrower, were used regularly by Homo Sapiens. At the end of the Upper Paleolithic, about 25,000 years ago, new hunting aids emerged, such as dogs, traps, and fishing hooks. Facts about this continual evolution of hunting weapons, necessarily accompanied by improvement of human cognition and skills, have been known for a long time; and yet, a unifying hypothesis for explaining these facts or attributing them to some change in the environment, was not proposed. In our research we have tried to address this challenge.”

In 2021 Prof. Barkai and Dr. Ben-Dor published a unified hypothesis, which explains the physiological and cultural evolution of Paleolithic humans, including the improvement of cognitive capabilities, as adaptations to mitigate declined energetic returns due to a progressive decline in prey size. The present study’s findings corroborate this hypothesis, following another study which they published last year together with zoologists Jacob Dambitzer and Prof. Shai Meiri of TAU. Surveying data from archaeological sites dating from 1,500,000 to 20,000 years ago, the 2022 study found that the dominant species of prey at the beginning of the period was a 12-ton elephant, and at the end it was a 25kg gazelle. In addition, the data indicate that the average weight of animals hunted by humans a million years ago was 3 tons, going down to 50kg 20,000 years ago. In other words, prey size decreased continually through time.