The work of James Tanner ... is replete with thought-provoking observations. His time as a pupil at Marlborough college appears, later, to have afforded him access to the records of the medical officer and the natural science master dating from 1873. Using these as a baseline, Tanner showed how the average height of the boys when aged sixteen and a half had risen by half an inch a decade over an 80-year period.
In Foetus Into Man (1978), he suggested that this "secular trend" was in part a consequence of improved nutrition, but also attributable to genetic factors. The latter included the increased incidence of procreation outside the village community, a key factor in which was the introduction of the bicycle.