Final answer:
The trend towards earlier adult height and sexual maturity observed over the past century is known as a secular trend, reflecting long-term generational physiological changes.
Step-by-step explanation:
The trend toward earlier attainment of adult height and sexual maturity, which began a century ago, is an example of a secular trend. A secular trend is a long-term pattern observed over generations, commonly related to physiological changes in the population. One notable secular trend in many parts of the world has been a decrease in the age at which puberty occurs, leading to earlier sexual maturity and the earlier achievement of adult height. This can be attributed to various factors including improvements in nutrition and health care.