Which came first, intelligence or civilisation?

Imagine two neighbouring valleys. One begins growing cereals while the other is still hunting and gathering. A thousand years later, the farming valley has higher genetic scores associated with education. What would that tell us about why the difference arose?

Perhaps the difference was already there. People with a greater capacity for learning, planning or innovation might have adopted a new way of life earlier. But the sequence could run the other way: a changed social environment could alter which traits helped people leave descendants, gradually changing the genetic composition of later populations.

The possibility of feedback between human evolution and economic life has a long history. Galor and Moav’s evolutionary growth model, for example, explicitly links selection and development. Finding a genetic association with an archaeological period does not tell us which part of that feedback we are seeing.

By archaeological stage, I mean a broad label for how people lived and the technology they used, such as the Neolithic farming period, Bronze Age or Iron Age. Different regions reached these stages at different times.

In Does Ancient DNA Track Archaeological Change?, I found that the fluid-intelligence genetic score was associated with later archaeological periods even after accounting for when people lived and giving each archaeological phase equal weight. The education and patience scores gave less consistent results.

This follow-up digs into the question that result leaves open. Did people with higher genetic scores reach the next archaeological stage earlier, or did a new way of life come first, followed by genetic change? I test both directions for fluid intelligence and educational attainment, then repeat the comparison with farming dates. The aim is to disentangle the causal arrow as far as these data allow, starting with temporal precedence: which change came first?

Figure 1 sets out the two possible sequences. Earlier archaeological settings predict higher later genetic scores most clearly after adjustment for genetic relatedness. The reverse prediction is uncertain. But following the same places through time leaves a much smaller sample, so that uncertainty gives me limited grounds for ruling out a role for earlier genetic differences. Farming gives a less clear answer in either direction.

Figure 1. Two histories that can produce the same later association

The clearest result points towards civilisation coming first: a more advanced archaeological setting predicts higher later intelligence and education genetic scores, especially after accounting for genetic relatedness. Upgrade to explore the rest of the story. Is there also evidence for the reverse arrow? Does farming produce the same pattern? Which archaeological transitions matter most? And could the smaller sample be hiding part of the answer?