To: longnshort who wrote (706362 ) 3/29/2013 10:26:51 PM From: Bilow 1 Recommendation Read Replies (1) | Respond to of 1578575 Hi longnshort; Re: 15-19 year generations. If you go to shorter generations, then my point is better; there's time for more mixing. But I'm just guessing on 20. I used 20 because I know that people used to get married at around age 13 and were having babies at 14. They kept having them to around 40, but a lot of women died in childbirth and didn't make it that long. So I picked 20. I kind of wonder what the average generation length is in the human species. Let's google it...Usually, a familial generation is defined as the number of years equivalent to the average age of a mother at the times she has her children, which for the sake of convenience is traditionally regarded as 25 years; in short, a generation is 25 years. Some define a familial generation as the average time between a mother's first offspring and her daughter's first offspring. Alternatively, the average generation length has been determined by the average age of women at first birth. In 2010, it was 25.4 years old (in the U.S.). [3] This is due to the place it holds in the family unit economics of committing resources toward raising children, and necessitating greater productivity from the parents, usually the male. Factors such as greater industrialisation and demand for cheap female labour, urbanisation, delayed first pregnancy and a greater uncertainty in relationship stability have all contributed to the increase of the generation length from the late 18th century to the present. These changes can be attributed to both societal level factors, such as GDP and state policy, and related individual level variables, particularly a woman's educational attainment. [4] In developed nations the average familial generation length is in the high 20s and has even reached 30 years in some nations. [5] As of 2008, the average generation length in the United States was 25 years, up 3.6 years since 1970. [6] Germany saw the largest increase in generation length over that time period, from 24 years in 1970 to 30 years in 2008. [5] Conversely, generation length has changed little and remains in the low 20s in less developed nations . en.wikipedia.org So 20 is about right for pre modern times. -- Carl