Why Did One Tool Stay the Same for a Million Years? Nobody Agrees

The form is a lump of stone, usually flint or quartzite, from which flakes have been struck all round both faces to produce a symmetrical pointed shape with a continuous cutting edge around most of its circumference. Making one requires planning several strikes ahead, controlling the angle and force of each blow and turning the piece repeatedly, which is a genuinely difficult skill that takes weeks of practice to acquire. The result is held in the hand rather than hafted, and sizes range from a few centimetres to specimens too large and heavy to use for anything.

The chronology is the part that unsettles people:

• •Earliest examples date from around 1.76 million years ago in Africa
• •The form spread across Africa, Europe and western Asia
• •It continued in use until roughly 300,000 years ago
• •That is over a million years of essentially the same design
• •Several human species made them, not only one
• •Modern humans appear well after the tradition had ended

Working out the function has occupied archaeology for a century and the evidence supports a general purpose rather than a specific one. Microscopic wear on the edges of excavated examples, compared against replicas used experimentally, indicates cutting meat, working hide and processing plants, with butchery the commonest. Experiments show the tool is genuinely effective for dismembering a large carcass, where the continuous edge and the weight both help. Suggestions that they were thrown as projectiles have been tested and are not supported for most examples. The awkward finds are the ones too large to hold, too small to grip and the ones showing no wear at all.

A site in southern England has produced a find that makes the social reading harder to dismiss. Excavation at Boxgrove recovered large numbers of these tools in an undisturbed layer alongside butchered animal remains, and a proportion of them are exceptionally well made, thin, regular and symmetrical far beyond what butchery requires, with no sign of use. Elsewhere, an enormous example from Furze Platt in Berkshire is over thirty centimetres long and weighs several kilograms, which no hand uses comfortably. Neither find proves anything about intent, and both are difficult to account for if the objects were purely functional and nothing else.

A tool that does not change for a million years is difficult to reconcile with any account of human behaviour based on innovation, and the explanations offered are all uncomfortable. One is that the makers lacked the cognitive flexibility to vary the design, learning it by imitation without understanding, which sits badly with the planning the manufacture requires. Another is that the form is simply an efficient solution and was not improved because it did not need to be, which fails to explain the absence of regional variation over such a span. A third is that the symmetry and the unused specimens indicate a social function, with well-made examples signalling the maker's skill, which is testable only indirectly.

Flaking both faces of a stone to a symmetrical point with an edge all round takes real skill and weeks to learn, and the resulting tool was made from around 1.76 million years ago until roughly 300,000 years ago with little change, by several human species across three continents. Wear analysis indicates general butchery and hide working. Nothing explains the stability comfortably.