Researchers have discovered 800,000-year-old footprints- the oldest ones outside Africa- in a river estuary in Norfolk, East of England.

The prints were found in an archaeological site in Happisburgh by researchers working on Ancient Human Occupation of Britain (AHOB) project. Researchers at British Museum, the Natural History Museum and Queen Mary University of London are part of the study, according to a news release.

The markings in the estuary were first discovered in May last year, according to BBC. Low tides exposed the footprints in the mud. The team had to work fast to photograph the markings before the water eroded the prints.

Their study published in the journal PLOS One, shows how the team found the markings.

"This is an extraordinarily rare discovery. The Happisburgh site continues to rewrite our understanding of the early human occupation of Britain and indeed of Europe," said Nick Ashton of the British Museum, according to the Guardian.

Researchers used a technique called Photogrammetry to create 3D models of the prints. They found that the prints belonged to a small group of people, including some children.

Anthropologists believe that the footprints might have been of our early cousins called Homo antecessor, or Pioneer Man, Telegraph reported. The discovery of the foot-prints of people in Europe could change the way researchers think about how ancient humans moved around the world.

"These people were of a similar height to us and were fully bipedal. They seem to have become extinct in Europe by 600,000 years ago and were perhaps replaced by the species Homo heidelbergensis. Neanderthals followed from about 400,000 years ago," Prof Chris Stringer at the Natural History Museum, according to the news release.

Read Ashton's Blog about the discovery, here.