Re: length of a generation
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In reply to:
Re: All humans are related.
Robert Stafford 6/07/04
You are absolutely right.Please forgive my error.
I actually quoted that span based on what I read
from the Mumma DNA Project, in which they
concluded that the average generation span
should be 33 years.Below is content cited
from the Mumma report, available at:
http://www.mumma.org/MummaDNA.pdfhttp://www.mumma.org/MummaDNA.pdf
MUMMA Generation time span - So how long a time is a generation?Some geneticists and anthropologists suggest 15 to 25 years as the number of years per generation.I believe this substantially understates the value for modern times, i.e. in the last 500 years.First, this time appears to be the time for the "first birth" of femalesand not an average time for the birth all of her children.For example, if we simply assume a woman's childbearing period was typically from age 15 to 45, the median child would be born around 15 years after hermarriage, suggesting an average generation time of 30 years, based on the mother's age.The second reason isthe typical male married somewhat later than females, often around age 25, so the average time from the father'sbirth to the average time when all of the children were born would be longer.To verify this, I determined theaverage male generation time span all of the Mumma surname participants was about 33 years and for theMomma/Reenstjerna families of Europe it was 34 years, thus confirming a longer time than is normally quoted.It was brought to my attention by Ann Turner that a published paper by Tremby & Vézina, American Journal ofHuman Genetics 66:651-658, 2000 reached similar conclusions.In their study, they determined an"Intergenerational Interval" of 34.4 years for men from family reconstruction.Using a time of 33 years as thetime per generation for Mumma males, a perfect match of 25 markers out of 25, 95% is not reached until around1000 years.Even at 50% probability, the median time that two men share a common ancestor is about 231years.