What are biological milestones primarily associated with?

Biological milestones are primarily linked to universal developmental events such as puberty because these milestones represent significant changes in an individual's physical and hormonal development that occur at approximately the same age across various cultures and environments. Puberty, for example, encompasses the onset of sexual maturation, changes in body composition, and the development of secondary sexual characteristics. This progression is biologically predetermined and is observed universally, highlighting it as a key aspect of human development.

In contrast, environmental factors that influence growth, personal achievements in physical health, and the impact of nutrition, although important in the broader context of development, do not represent the biological milestones that define stages like puberty. These other factors can certainly affect an individual's development but are not universal milestones themselves.