Some of the first Britons were cannibals - but not all of them, reveals ground-breaking new research.

Analysis of the UK's oldest human DNA obtained from the remains of people who lived in caves over 13,000 years ago indicates the presence of two groups - with "distinct" origins and cultures - that migrated to Britain at the end of the last Ice Age.

And one of those groups - who lived in Gough's Cave in Cheddar in Somerset - practiced ritualistic cannibalism, say scientists.

But there is no evidence that the other group - based in present day Wales - were cannibals, according to the study.

Researchers explored DNA evidence from a female found at Gough's Cave, and a male from Kendrick's Cave in North Wales, who both lived more than 13,500 years ago.

Very few skeletons of that age exist in Britain, with around a dozen found across six sites in total.

The pioneering research, which involved radiocarbon dating and analysis as well as DNA extraction and sequencing, has shown that it is possible to obtain useful genetic information from some of the oldest human skeletal material in the country.

The study, published in the journal Nature Ecology and Evolution, was conducted by scientists from University College London's Institute of Archaeology, the Natural History Museum and the Francis Crick Institute in London,

They explained that the genome sequences now represent the earliest chapter of the genetic history of Britain - but ancient DNA and proteins promise to take us back even further into human history.

The team said that DNA from the Gough's Cave female, who died about 15,000 years ago, indicates that her ancestors were part of an initial migration into north west Europe around 16,000 years ago.

However, the individual from Kendrick's Cave is from a later period, around 13,500 years ago, with his ancestry from a western hunter-gatherer group.

The researchers say that group's ancestral origins are thought to be from the near East, migrating to Britain around 14,000 years ago.

Study co-author Dr Mateja Hajdinjak, of the Francis Crick Institute, said: "Finding the two ancestries so close in time in Britain, only a millennium or so apart, is adding to the emerging picture of Palaeolithic Europe, which is one of a changing and dynamic population."

The researchers noted that those migrations occurred after the last Ice Age when around two-thirds of Britain was covered by glaciers.

As the climate warmed and the glaciers melted, "drastic" ecological and environmental changes took place and humans began to move back into northern Europe.

Co-author Dr Sophy Charlton said: "The period we were interested in, from 20,000 to 10,000 years ago, is part of the Palaeolithic – the Old Stone Age.

"This is an important time period for the environment in Britain, as there would have been significant climate warming, increases in the amount of forest, and changes in the type of animals available to hunt."

As well as genetically, the team said that the two groups were found to be "culturally distinct" - with differences in what they ate and how they buried their dead.

Co-author Dr Rhiannon Stevens, of UCL's Institute of Archaeology, said: "Chemical analyses of the bones showed that the individuals from Kendrick's Cave ate a lot of marine and freshwater foods, including large marine mammals.

"Humans at Gough's Cave, however, showed no evidence of eating marine and freshwater foods, and primarily ate terrestrial herbivores such as red deer, bovids - such as wild cattle called aurochs - and horses."

The research team also discovered that the mortuary practices of the two groups also differed. Although there were animal bones found at Kendrick's Cave, those included portable art items, such as a decorated horse jawbone.

No animal bones were found that showed evidence of being eaten by humans, and the scientists say that indicates the cave was used as a burial site by its occupiers.

In contrast, animal and human bones found in Gough's Cave showed "significant" human modification, including human skulls modified into "skull-cups" - which the researchers believe to be evidence for ritualistic cannibalism.

They said individuals from that earlier population seem to be the same people who created the Magdalenian stone tools, a culture known also for iconic cave art and bone artefacts.

Gough's Cave is also the site where Britain's famous Cheddar Man was discovered in 1903, dated to around 10,000 years ago.

Cheddar Man was found to have a mixture of ancestries, mostly (85 per cent) western hunter-gatherer and some (15 per cent) of the older type from the initial migration.

Co-author Dr Selina Brace, of the Natural History Museum, added: "We really wanted to find out more about who these early populations in Britain might have been.

"We knew from our previous work, including the study of Cheddar Man, that western hunter-gatherers were in Britain by around 10,500 years Before Present, but we didn't know when they first arrived in Britain, and whether this was the only population that was present."

The human remains from Kendrick's Cave are on display at Llandudno Museum, and those from Gough's Cave at the Natural History Museum.