On a dry bank of the Turkwel River in northern Kenya, about a hundred and eighty kilometres west of Lake Turkana, there is a scatter of teardrop-shaped stones that people made 1.76 million years ago.
The place is called Kokiselei. In place of today's arid ground, the site was then a wooded riverbank at the edge of a large lake, in a wet-dry savannah crowded with hippos, elephants, and the people who left these tools. The stones are bifaces: worked on both faces, carefully symmetrical, thin at the edges, thick through the middle, small enough to hold in one hand or two. The Victorians who first classified similar tools in Europe called them handaxes, which was a guess about function that the archaeological record has never quite settled.
The reason to care about them isn't that they exist, which is unremarkable for stone. It's that the same design was still being made in roughly the same way over a million years later, in another continent, by people we don't recognise as biologically identical to their makers. The tradition persisted for something like 1.7 million years. That's more than three hundred times the span of our recorded history.
You can't invent a biface in a lifetime. Making one requires you to look at a fist-sized cobble of flint or chert and see, in advance, the tool inside it. Then you have to remove flakes in a specific sequence, with the right angle, striking with the right amount of force, alternating sides so the piece stays symmetrical and thin. A single misplaced strike can shatter the whole thing. There are more ways to fail than to succeed.
Which means that every biface anyone has ever recovered represents a chain of teaching that went unbroken for the length of a life. Someone had to show someone else. Not by words, presumably, since we can't know when spoken language emerged, but by demonstration, correction, patient repetition. And the person taught did the same for the next person, and the next, and the sequence held long enough that when the design finally faded from the toolkit around 200,000 years ago, it had been the dominant technology of the human line for longer than our species has existed.
This was the first infectious idea we have evidence for. The first thing too good not to pick up and pass on. Before writing, before agriculture, before the campfire's mythology, there was a design in a stone, held in the mind of one person, moved into the mind of another, and preserved by the simple act of showing. It's the essence of being human, and it precedes what we recognise as human by a margin of more than a million years.
The machines have brought the question of inherited ideas back to the surface. We're anxious now about who owns what, who thought of it first, whose language is being averaged into the model's next most likely token. These are fair questions, but they're new versions of a very old one. Ideas have always travelled. They have always been remade in the hands of the next holder. The biface was carried forward, unbroken, for a million and a half years by a species that couldn't write and may not have been able to speak.
Whatever you're worried about the machines doing to your work, humans have been doing to each other's for a long time.
Part one of a short series on how ideas travel. Piece two, on what happens when a machine reads your writing, is out next week. Plan B builds brands built to survive being passed forward. Get in touch.
