An extreme cooling event in Europe caused an extinction of early humans on the continent around 1.1 million years ago, a study suggests.

The abrupt climate changes saw ocean surface temperatures off Lisbon dropping below 6C – conditions that would have made it hard for archaic humans to survive, according to the researchers.

The UCL scientists said their findings, published in the journal Science, challenge the widely held belief that after arriving from South-West Αsia by about 1.4 million years ago, these humans were able to survive through multiple climate cycles and adapt to increasingly harsh conditions.

Senior author Professor Chronis Tzedakis, of UCL Geography in London, said: “Our discovery of an extreme glacial cooling event around 1.1 million years ago challenges the idea of continuous early human occupation of Europe.”

Along with UCL, paleoclimate scientists from the University of Cambridge and CSIC Barcelona analysed the chemical composition of marine micro-organisms and examined the pollen content in a deep-sea sediment core recovered off the coast of Portugal.

Cores such as these can show a glimpse of the Earth’s past geology and climate.

To our surprise, we found that this cooling at 1.1 million years ago was comparable to some of the most severe events of recent ice ages

Lead author Dr Vasiliki Margari, of UCL Geography, said: “To our surprise, we found that this cooling at 1.1 million years ago was comparable to some of the most severe events of recent ice ages.”

Co-author Professor Nick Ashton of the British Museum said: “A cooling of this magnitude would have placed small hunter-gatherer bands under considerable stress, especially since early humans may have lacked adaptations such as sufficient fat insulation and also the means to make fire, effective clothing or shelters.”

The experts then ran a climate simulation to capture the extreme conditions during this time.

Study co-author Professor Axel Timmermann, of the IBS Centre for Climate Physics at Pusan National University in South Korea, said: “The results showed that 1.1 million years ago climate around the Mediterranean became too hostile for archaic humans.”

Combined results suggest that Iberia, and more generally southern Europe, became devoid of human population and remained so for the next 200,000 years.

Study co-author Professor Chris Stringer of the Natural History Museum in London said: “According to this scenario, Europe may have been recolonised around 900,000 years ago by more resilient humans with evolutionary or behavioural changes that allowed survival in the increasing intensity of glacial conditions.”

Meanwhile, another study, also published in the journal Science, suggests climate change may have facilitated interbreeding between two groups of ancient human relatives: Denisovans and Neanderthals.

Back in 2018, scientists found evidence of a woman, nicknamed Denny, who lived 90,000 years ago and had a Denisovan father and a Neanderthal mother.

Simulations paleo-biologists from South Korea and Italy showed Neanderthals and Denisovans had different environmental preferences, with Denisovans more adapted to cold environments, such as boreal forests and tundra, while their Neanderthal cousins preferred temperate forests and grassland.

But in warm interglacial periods, when Earth’s orbit around the Sun was more elliptic and northern hemisphere summer occurred closer to the Sun, simulations suggest their habitats may have begun to overlap geographically.

Prof Timmermann, who is also one of the authors on the second study, said: “When Neanderthals and Denisovans shared a common habitat, there were more encounters and interactions among the groups, which would have increased the chance of interbreeding.”