One billion A.D. A question for evolution fans.

[leo-rcc]

In order to figure out the 25 years you mention (I am not doubting that the figure must come from somewhere) I did find this:

http://historymedren.about.com/library/w...12200c.htm

On infant mortalitiy rate:

The highest estimated percentage I have encountered is a 50% death rate, although 30% is the more common figure. These figures include the high number of infants who died within days after birth from little-understood and wholly unpreventable illnesses that modern science has thankfully overcome.

Now if we take the 30% as the low figure, and 25 as the average life expectancy, that means you would need 30% of the population to live to the age of 50-60.

Also this one I found:

http://www.hyw.com/books/history/Fertilit.htm

The biggest danger for all children was surviving childhood, particularly the first few years, when a childs immune system was getting itself organized. After that, males had to worry about accidents (most of the population engaged in manual labor, and the nobles had hunting accidents and the rigors of warfare to worry about.) Once a male passed age 40, and became an "old man," he generally stayed away from dangerous activities and had good prospects of living to a ripe old age.

If your sources say 25 years, and my book from 1990 says 30 to 35, it might be that in the 18 years the figure is dropped in light of new evidence. But that doesn't mean that people just dropped dead at 25 years of course.