How long is a 'generation'

[tarchon]

Historians refer to generations as being every 20 years. So that is the accepted definition in historical writings of peer written historical references.

That's "generation" in the sense of "cohort", like "Generation X." If you take it to mean "step between between an ancestor and a descendant," the number is usually at least 25 years. Bible prophesy figurers often use it to mean "average life span."

 

[Dr. Strangemonkey]

20 is what I've always heard used for generations outside of the twentieth century.

I've only heard 25 used as a very current development.

Though I would also guess that men would have longer generations than women as a general rule of averages.

 

[tarchon]

20 is what I've always heard used for generations outside of the twentieth century.

I've only heard 25 used as a very current development.

20 could be the number used for generation as "age of maturity," though I'd still think that's a little low.

25+ has been the norm for at least the past 500 years, the period when there's enough recorded genealogical data to make reasonable estimates. Just go to a genealogy site, grab some random family tree, and follow it back 300 years. It's remarkably consistent if you spread it out over several centuries to reduce the noise. There are several factors that pull the number up over the naive expectation. I'll repeat the main one, that it includes not only the 1st child, who was indeed generally born in the 15-20 range (for women, add a few years for men), but also the last, who was quite frequently born in the 30-40 age range. If you include both males and females (some do, some don't), it's pulled up even more by that fact that it was a lot more common for 50 year old men to father children than for 10 year old boys to father children, and it doesn't take too many "old dads" to pull the average up quite a bit. This effect is reduced if you use medians. Nowadays, people have fewer children generally, but they wait longer to have them, so for the most part the generation length hasn't moved too much.
See for example:
http://www.unc.edu/~rowlett/units/dictG.html
http://archiver.rootsweb.com/th/read/GOONS/2002-05/1020466344
http://www.demographic-research.org/volumes/vol10/7/10-7.pdf

It's probably been of a similar length back into prehistory:
"A generation time of 30 years in human populations was suggested by the recent studies by Tremblay and Vezina (2000) and Sigurdardottir et al. (2000) and will be retained throughout this paper for all estimations involving Homo sapiens populations." - http://www.journals.uchicago.edu/AJHG/journal/issues/v69n5/013122/013122.html

 

[Treebore]

Geneologically speaking I have no doubt you are correct. When you talk to the historians who write our history books most of them use 20 years as the defintiion of a generation. However, since there is no set of rules for all historians to use or write by, even they are confused and confusing.

So it boils down to there being no universally accepted or mandated definition for a generation, unless you want to use a governments definition.

 

[Tonguez]

Geneologically speaking I have no doubt you are correct. When you talk to the historians who write our history books most of them use 20 years as the defintiion of a generation. However, since there is no set of rules for all historians to use or write by, even they are confused and confusing.

So it boils down to there being no universally accepted or mandated definition for a generation, unless you want to use a governments definition.

Of course the US Standards and British standards are often very different - the British standard as used in my country of residence is 25

 

[Ranger REG]

If I'm wanting to describe a certain amount of time passing in terms of generations of a family, roughly how many years does a generation cover? For example, rather than say "his family was cursed for 1000 years", I want to say "his family was cursed for x generations", but want x to work out somewhat close to 1000 years.

This is assuming a human family, but for the sake of argument how would longer-lived races change the equation?

In medieval times, I'd say roughly 18 years. A child becomes an adult at around 16 years of age, at which time the man start to look for a wife and immediately start a family afterward. If he is from a family of high standing, marriages are already arranged by his parents to ensure that their son will have the best security in his future before they die.

 

[jester47]

Just for added information:

It might give your world a little versimilitude if you make it a family that has a smaller or larger than average generation gap.

For example, my family. Our generation gap is huge. (which is probably why we are so into history). My great grandfather (yes one great) fought in the american civil war. My grandfather was in WWI in France. Go six generations you are in the mid to late 1700's. As a counterpoint I know teenagers who's grandfathers fought in Vietnam.

Aaron

 

[tarchon]

Geneologically speaking I have no doubt you are correct. When you talk to the historians who write our history books most of them use 20 years as the defintiion of a generation. However, since there is no set of rules for all historians to use or write by, even they are confused and confusing.

Well, of those four links I listed only the second one is from a genealogy source, and it's quoting from a demographic study, even if it is on a genealogy board. This isn't a concept limited to the little old ladies down at the LDS library.
I also have to say that I'm not entirely ignorant of historiography, and this is the first time I've ever heard any one say that there was a fixed standard definition for the length of a "generation" as a cohort. My impression is that they are more typically defined according to demographic trends and influential conditions that persist in a society during the childhood of the particular cohort, the "Baby Boom" for example. It would be ridiculous to define a "Depression" generation and arbitrarily cut it off at, say, 1949 just because that's 20 years after the Depression. Ok, maybe on the History Channel, but I'm not talking about histotainment.

I note also http://www.hyperdictionary.com/dictionary/generation
"4. A single step or stage in the succession of natural
descent; a rank or remove in genealogy. Hence: The body of
those who are of the same genealogical rank or remove from
an ancestor; the mass of beings living at one period;
also, the average lifetime of man, or the ordinary period
of time at which one rank follows another, or father is
succeeded by child, usually assumed to be one third of a
century; an age." - Websters, 1913.

 

[Treebore]

I'm not ignorant either. I took the requisite history classes in college and I read a fair amount of history books for enjoyment and for home schooling my children. The one I asked about this is my wife, who holds a BA in History and a BS in Biology.

But I believe that outside of the government there is no "standard" definition. The US government definition of a generation is 25 years in the Census Bureau, at least it was when I worked for them during the 2000 Census. So if nothing else this proves there should be a "standard" definition so no one will get into any more debates about it.

 

[ssampier]

May I ask why generation is more useful than precise or approximate years? Unless, of course, you're referring to long family line, "My great, great, great, grand father of old owned this land. The blood of the Old flows through you young man, fight for it back."