Question

"when physical characteristics, such as early onset of menstruation or increased height and weight (due to better nutrition), change over the course of several generations, this is an example of a

Answer 1

This is a secular trend, which is a pattern of change over several generations. It is a variation of the expression of the organism based on the environment. An example of a secular trend is that puberty is now happening earlier on average, than it has in the past, for both boys and girls.