The model proposed by Henrich (2004), which is often cited as a theoretical basis for understanding the role of demography in the cumulative cultural evolution of technology, is expounded for general readers and reanalyzed through a novel approach based on the concept of innovation rate. In this analysis, the model is generalized to allow a broader class of distributions for the distribution of individual skill levels, while preceding studies explored only the cases of Gumbel, logistic, and normal distributions. It is revealed that the expected number of innovators per generation is a key determinant of the sign and tempo of technological growth. In particular, the maximum skill level in a population grows cumulatively when the expected number of innovators per generation exceeds a certain threshold. Based on the results of the theoretical discussion, existing experimental tests of the model and related demographic hypotheses are reevaluated in the latter half of the article, while remarks are made on future possible tests of the model from a quantitative perspective.
