In general we think of a generation being about 25 years- from the birth of a parent to the birth of a child. We also generally accept that the length of a generation in earlier periods of history was closer to 20 years when humans mated younger and life expectancies were shorter.
However, generation lengths are not certain and keep evolving. We are now already starting to consider that a generation could be longer than the accepted 25 years. Men could be at least a third longer, so 35 –year generations with women one-sixth longer, 30 –year generations.
Why Age Matters
In genealogy and family history work, the length of a generation can be a really helpful way to check your research. If you had a generation gap of say 35 years or more, it may be worthwhile looking into this a bit further. What you could find is that you’ve missed a generation, or that information on two different individuals has been linked to the same person. This type of discovery could then lead you on to the same person.
Your Generation
Because generation lengths help us to spot missing information in our lineage, it is good idea to decide what generation length suits you. If you are looking back at ancestors 50 or more generation in the past, using the ‘accepted’ 20 or 25 years as a conversion factor could underestimate the time interval. But if you’re looking only a few generations and you want to convert generation to years, using 30 to 35 year generation gap, or even one that you’ve developed based on your own family history research, is a great place to start.
You could then check the accuracy of these generation periods by comparing all-male or all female ranges in your family lines for a chosen period. Then you could see how closely the intervals agree with the number of years you are using to estimate a generations.