A record of ancient life
In May 2013, a storm and heavy tides scoured the sand from the beach at Happisburgh, Norfolk. This erosion exposed a section of laminated silts, part of a geological formation known as the Cromer Forest Bed. Researchers from the British Museum and other institutions, who were already studying the area for its prehistoric significance, noticed a series of unusual hollows spread across a 12-square-meter area of the newly revealed mudflat.
The team immediately recognized the shapes as possible hominin footprints. They were in a race against time. The exposed silt layer was in the inter-tidal zone, and each new tide threatened to wash the delicate impressions away forever. Over the next two weeks, working in difficult conditions, scientists used a technique called photogrammetry to take hundreds of overlapping photographs. This allowed them to create a detailed and permanent 3D digital model of the surface just before the sea completely destroyed it. Analysis confirmed the discovery: these were the oldest hominin footprints ever found outside of Africa.
The dating of the site was established using several methods. The sediments are too old for radiocarbon dating. Instead, geologists used palaeomagnetism and biostratigraphy. Magnetic signatures in the sediment show they were laid down before the last major reversal of Earth's magnetic field, the Brunhes-Matuyama reversal, which occurred around 780,000 years ago. The presence of certain extinct vole species and other animal fossils helped to further constrain the age to between 850,000 and 950,000 years old.
Reading the ancient tracks
The 3D models of the footprints provided remarkable information about the individuals who made them. Analysis identified the tracks of at least five individuals, a mixed group of adults and children. The foot lengths ranged from 140 to 260 millimeters, which allowed scientists to estimate the heights of the individuals as between 0.9 meters (2 ft 11 in) and 1.7 meters (5 ft 7 in). The prints showed a clear heel, arch, and even toe impressions, indicating a modern, bipedal walking gait.
No human fossils have been found at Happisburgh, but the likely candidate for the printmakers is Homo antecessor, or "Pioneer Man." Fossils of this early human species have been discovered at a broadly contemporaneous site in Atapuerca, Spain. The Happisburgh group was walking south along the muddy edge of a major river estuary. This was not the modern Norfolk coast but a river valley plain, bordered by coniferous forest, with a climate similar to that of southern Scandinavia today.
This ancient river system was a precursor to the River Thames, which followed a more northerly course at the time. The area had many resources. The hominins shared this area with animals like southern mammoths, extinct horses, giant deer, and rhinos. The group may have been foraging for food like shellfish and edible plants on the mudflats. Their presence in such a northerly, cool-climate location changes previous ideas about the environmental tolerances of early humans.