The “infinitesimal model”, coined by R.A. Fisher, proposes that human traits are influenced by an infinite number of independent genetic variants each with an infinitely small additive effect, in addition to environmental variation. This fantastical model, developed over a century ago, now appears to be a pretty good approximation of the true genetic architecture of common human traits (of course, humans do not have an infinite number of genes).
Barton et al. 2017.