During the warm periods between ice ages stretching from 500,000 to 200,000 years ago, the southern parts of Britain were occupied by a species of ancient human, Homo heidelbergensis. These hunter-gatherers were quite sophisticated in where they chose to live or camp, always mindful of where good food could be found. Unfortunately they left little evidence of their occupation except for very rare butchery sites, strewn with cut-marked bones. But they did leave thousands of stone tools, particularly Acheulian knapped-flint hand-axes.
In a paper published in the journal PLOS One, my Southampton colleagues Laura Basell, Sian Robinson, Graham Burdge and I analysed data from archaelogical sites on either side of the English Channel to examine whether their location could be linked to areas where there was once a rich variety of food. These sites are concentrated in the middle-lower reaches of river valleys, with most being upstream of, but relatively close to, the estimated tidal limits of sea levels of the time. They include Dunbridge in Hampshire, Swanscombe near Dartford, and the Somme Valley in France.
Due to the effects of geological processes over such huge spans of time, only a few of these sites are exactly where they were hundreds of thousands of years ago. Even so the rest have only moved by a few tens of metres. So by comparing the sites' locations to a database of plants and animals known throughout the region at the time we can estimate the food available to them.
Just how well were our early ancestors' nutrient needs met by the food available in what was then an almost entirely forested region? We looked at the availability of macronutrients (proteins, carbohydrates, and fats) and essential micronutrients such as vitamins A, B6, B12, and C, folic acid, iodine, iron and zinc. The advantage of these sites included better access to foods that provided all these critical dietary elements, including sources such as raw liver and bone marrow, eggs, fatty beaver tails, highly nutritious eels, root vegetables such as wild carrots, cabbage, watercress, and leafy green vegetables. This will have maintained the population’s health and maximised reproductive success, and may even have contributed to increasing their cultural complexity.
Downstream floodplains are shown to be the optimum locations in the nutritional landscape for a broad diet. In fact such places may have been seen as good, or healthy or “special” places, explaining the high number of artifacts built up by repeat visits or occupation.
Stone tools are found in small numbers along the entire length of river valleys and hill tops across southern England and northern France, which shows that these hominins travelled throughout the landscape. But the best explanation for the high concentration of stone tools found only in these downstream locations is that they provided the best foods – particularly those in short supply in what was then a entirely forested landscape. Combined with other benefits on site such as flint for tool-making, beavers pelts for fur clothing, and safety on small islands in river channels from predators such as big cats, the high nutrient diversity made these locations the optimal locations in northwest Europe.
So there was perhaps a symbiotic interaction in the ecological niches found at these floodplain sites between these early hominins, horses and deer attracted to the grassland at the edges of forests, freshwater fish and eels, and beavers. It seems that this pattern of occupation coupled with low population densities was fundamental to the Palaeolithic diet. Here, in the occasionally glaciated higher latitudes of the northern hemisphere – the very edge of the world at the time – it allowed our early human ancestors to expand beyond their homelands and into these less productive regions for over half a million years.
It seems that the nutritional benefits to be had at these locations led them to be used as central points, from which a healthy variant of the Palaeolithic diet allowed the hominins to extend their reach through the landscape. While we have very little information on their lifespan, their site distribution suggests they had a balanced diet and did not suffer from many of the “diseases of civilisation” that appear after the adoption of agriculture.