Early humans changed ecosystems long before farming

Humans weren’t just along for the ride in prehistoric Europe – they were already changing the world around them.

Long before farming or permanent villages, small groups of hunter-gatherers were shaping the land. We are only just beginning to understand what this involved.

A new study suggests that these early people didn’t just adapt to nature – they influenced it. Through hunting and fire, even Neanderthals left a visible mark on Europe’s landscape, tens of thousands of years ago.

Not just passengers on the landscape

Most people assume that human influence on the environment began with agriculture, around 10,000 years ago. But evidence from this study suggests otherwise.

Both Neanderthals and early modern humans were active players in shaping Europe’s ecosystems tens of thousands of years before that.

Scientists used computer simulations to figure out how climate, wild animals, fires, and people affected vegetation in the past. The study considered two warm periods in Europe’s past: the Last Interglacial period (about 125,000 to 116,000 years ago) and the Early Holocene (about 12,000 to 8,000 years ago).

The team then compared the simulations with data from fossilized pollen in order to assess how human activities may have shaped vegetation cover. What they found changes the story.

Humans – the missing piece

Once the researchers added human activity into the equation – like hunting and using fire – the data made a lot more sense.

“It became clear to us that climate change, large herbivores and natural fires alone could not explain the pollen data results,” said Jens-Christian Svenning, a biology professor at Aarhus University who was involved in the research.

“Factoring humans into the equation – and the effects of human-induced fires and hunting – resulted in a much better match,” he added.

Burning and hunting changed the land

In the Last Interglacial period, Neanderthals lived alongside massive herbivorous animals like elephants, rhinoceroses, aurochs, bison, and horses.

By the Early Holocene, when Homo sapiens were present, many of those species had disappeared or declined sharply in number. Hunting played a major role.

“The Neanderthals did not hold back from hunting and killing even giant elephants. And here we’re talking about animals weighing up to 13 tons! Hunting also had a strong indirect effect: fewer grazing animals meant more overgrowth and thus more closed vegetation,” explained Svenning.

“However, the effect was limited, because the Neanderthals were so few that they did not eliminate the large animals or their ecological role – unlike Homo sapiens in later times.”

The simulations showed that the actions of Mesolithic hunter-gatherers could have influenced up to 47 percent of the distribution of plant types, as herbivore numbers fell and forests grew thicker.

“The Neanderthal effect was smaller, but still measurable – approximately 6% for plant type distribution and 14% for vegetation openness,” said study lead author Anastasia Nikulina from Leiden University.

A new look at ancient humans

“The Neanderthals and the Mesolithic hunter-gatherers were active co-creators of Europe’s ecosystems,” said Svenning.

Nikulina added that the study results are consistent with both ethnographic studies of contemporary hunter-gatherers and archaeological finds.

“The study goes a step further by documenting how extensive human influence may have been, tens of thousands of years ago – that is, before humans started farming the land,” she explained.

How the research was conducted

The study combined a huge amount of data and advanced computer modeling. Data on fossil pollen from across Europe was used, and thousands of different scenarios were tested.

The researchers were then able to narrow down the most likely explanations for the pollen distributions observed.

“This is the first simulation to quantify how Neanderthals and Mesolithic hunter-gatherers may have shaped European landscapes,” said Nikulina.

“Our approach has two key strengths: it brings together an unusually large set of new spatial data spanning the whole continent over thousands of years, and it couples the simulation with an optimization algorithm from AI.”

According to Nikulina, the approach allowed her team to run a large number of scenarios and identify the most possible outcomes. The simulations made it clear that humans couldn’t be left out of the story.

“To understand the vegetation at that time, we must also take human impacts into account – both direct and indirect. Even without fire, hunter-gatherers changed the landscape simply because their hunting of large animals made the vegetation denser,” said Svenning.

Future research directions

While this study offers a big-picture view of how ancient humans changed Europe’s landscapes, the researchers say there’s still more to learn.

They want to run similar simulations in other parts of the world – like the Americas and Australia – where Homo sapiens arrived without any earlier human species already there.

The experts also noted that local studies will be important for understanding how these big patterns played out in specific places.

“Although the large models paint a broad picture, detailed local studies are absolutely essential to improve our understanding of the way humans shaped the landscape in prehistoric times,” concluded Svenning.

The full study was published in the journal PLOS One.

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