Disappearing megafauna may have prompted a stone tool revolution

A drop in the number of huge animals 200,000 years ago may have forced ancient humans to abandon heavy-duty stone tools in favour of lightweight toolkits to hunt smaller animals. That’s according to a new study that supports the idea that switching to smaller prey may have boosted our ancestors’ intelligence.

For over a million years, several early human species used similar kinds of heavy stone tools, such as axes, cleavers, scrapers and stone balls. Evidence suggests such tools were used for killing and butchering massive plant-eating prey, or megaherbivores, including now-extinct relatives of elephants, hippopotamuses and rhinos.

Then, between 400,000 and 200,000 years ago, smaller, more sophisticated tools began to appear alongside heavy tools. Our species, Homo sapiens, emerged in the middle of this period.

Around 200,000 years ago, heavy tools curiously disappeared from the archaeological record in the Levant. Meanwhile, there was an increase in the number of small, lightweight stone toolkits, including blades and precision scrapers, which were more sophisticated and diverse.

Now, Vlad Litov at Tel Aviv University, Israel, and his colleagues have found a link between the apparent technological shift and a dramatic decline in large plant-eating mammals at the time, which were possibly decimated by overhunting.

The researchers catalogued the archaeological finds from 47 known sites across the Levant throughout the Palaeolithic, which lasted from around 3.3 million to 12,000 years ago. When they cross-referenced all the dated stone-tool artefacts with animal remains from each site, an intriguing pattern emerged.

The team discovered that, after 200,000 years ago, when heavy-duty technologies disappeared from the record, there was a significant drop in the relative abundance, specimen count and contribution to biomass of megaherbivores heavier than 1000 kilograms. Meanwhile, the presence and availability of smaller prey increased along with the number of more sophisticated small tools.

Bolstering the connection between stone tools and prey types, the team also points out that previous studies have shown that heavy-duty tools persisted until around 50,000 years ago in other regions where large prey remained available, such as in southern China.

Earlier ideas suggested the technological shift probably occurred due to humans already being smarter and more innovative, possibly due to unknown evolutionary pressures and advantageous genetic mutations. But Litov and his team think the findings support a different idea that they have previously proposed: that a reliance on smaller prey drove the evolution of big brains in modern humans.

“As megaherbivores declined, humans increasingly relied on smaller prey, which required different hunting strategies, more flexible planning, the use of lighter and more complex toolkits,” says Litov. “These challenges selected for enhanced cognitive abilities, meaning cognition evolved as part of this new adaptive system rather than driving it from the outset.”

“I would argue there is more to it than just prey size,” says Ceri Shipton at University College London. He says studies have shown there was cognitive change and more sophisticated planning already going on in the Middle Palaeolithic, with tentative evidence for mass hunting of medium-sized ungulates, including horses and bison.

Nicolas Teyssandier at the French National Centre for Scientific Research also has reservations. “If humans adapted to new fauna, this reflects adaptation rather than pure intelligence,” he says. “It was equally intelligent to produce and select heavy-duty technologies for hunting and consuming large megaherbivores.”

Litov acknowledges that his and others’ previous work points to high cognitive capabilities already present in early stages of human evolution, particularly in Homo erectus, which appeared roughly 2 million years ago. But he maintains that the shift from large to small prey had a profound effect on humans. A single carcass of an ancient elephant could have fed a band of around 35 hunter-gatherers for months. If such high-calorie resources disappeared, turning to smaller prey would result in lower returns per animal, he says.

“From an energetic standpoint, they had to acquire dozens of smaller ungulates, such as fallow deer, to compensate for the loss of a single elephant,” says Litov. This could have driven a range of cognitive and behavioural changes, including increased coordinated hunting of elusive prey, the development of more complex technologies, and increased social cooperation and planning. “These demands may have contributed to the selection for larger brains in later species, including Neanderthals and Homo sapiens,” he says.

“My personal view is that a decline in the large prey that hominins were used to may have increased competition between groups,” says Shipton. “In reality, it was probably an iterative process where decline in larger prey drove cognitive change, which, in turn, enabled access to smaller prey.”

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