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<blockquote data-quote="tarchon" data-source="post: 1776632" data-attributes="member: 5990">20 could be the number used for generation as &quot;age of maturity,&quot; 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.&nbsp; Just go to a genealogy site, grab some random family tree, and follow it back 300 years.&nbsp; It's remarkably consistent if you spread it out over several centuries to reduce the noise.&nbsp; There are several factors that pull the number up over the naive expectation.&nbsp; 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.&nbsp;&nbsp; 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 &quot;old dads&quot; to pull the average up quite a bit.&nbsp; This effect is reduced if you use medians.&nbsp; 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:<a href="http://www.unc.edu/~rowlett/units/dictG.html" target="_blank">http://www.unc.edu/~rowlett/units/dictG.html</a><a href="http://archiver.rootsweb.com/th/read/GOONS/2002-05/1020466344" target="_blank">http://archiver.rootsweb.com/th/read/GOONS/2002-05/1020466344</a><a href="http://www.demographic-research.org/volumes/vol10/7/10-7.pdf" target="_blank">http://www.demographic-research.org/volumes/vol10/7/10-7.pdf</a>It's probably been of a similar length back into prehistory:&quot;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.&quot; - <a href="http://www.journals.uchicago.edu/AJHG/journal/issues/v69n5/013122/013122.html" target="_blank">http://www.journals.uchicago.edu/AJHG/journal/issues/v69n5/013122/013122.html</a></blockquote>

[QUOTE="tarchon, post: 1776632, member: 5990"] 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: [url]http://www.unc.edu/~rowlett/units/dictG.html[/url] [url]http://archiver.rootsweb.com/th/read/GOONS/2002-05/1020466344[/url] [url]http://www.demographic-research.org/volumes/vol10/7/10-7.pdf[/url] 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." - [url]http://www.journals.uchicago.edu/AJHG/journal/issues/v69n5/013122/013122.html[/url] [/QUOTE]

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