Why do generations differ so much in duration?

Question

I have always wondered why some generations are widely recognised to last ~15 years, others 18, some others 25. What even constitutes a generation?

In: Biology

Answer 1

Generations are artificial. We make them up because they describe rough social patterns. Their boundaries are always fuzzy and awkward, and often more defined by “were you alive to experience X” than anything else.

The 25-year figure is usually used more by genealogists and anthropologists, looking at the long span of human history. Most people have their first child somewhere between 20 and 25 in the modern world.