Sorry, we don't allow throughout history questions. These tend to produce threads which are collections of trivia, not the in-depth discussions about a particular topic we're looking for. If you have a specific question about a historical event or period or person, please feel free to re-compose your question and submit it again. Alternatively, questions of this type can be directed to more appropriate subreddits, such as /r/history or /r/askhistory.

It may also be worth trying /r/AskAnthropology or /r/AskScience (biology category, i.e. for geneticists studying human genome and world populations) as they may use typical averages for the number of generations in a given timespan, from which could be derived the average age of a mother, and thus grandmother.