An ancestor is someone from whom you are descended: your parents, grandparents, great-grandparents, and so on back through the generations. Your ancestors are the people whose lives led eventually to yours.

When you trace your family tree, you're discovering your ancestors. Maybe you'll find a great-great-grandmother who immigrated from Ireland, or a great-great-great-grandfather who fought in the Civil War. Each of these people is your ancestor, connected to you through an unbroken chain of parents and children stretching across time.

Your ancestors went before you, living their lives, making their choices, and eventually having the children who would have children who would, generations later, include you. Some people study their ancestors through genealogy, searching old records and documents to learn where they came from and how they lived.

Scientists also use ancestor to describe earlier species from which modern species evolved. Birds, for example, are descended from dinosaur ancestors that lived millions of years ago. In this way, understanding ancestors helps us understand how we got here, whether we're talking about our own families or the history of life on Earth.