What was the average life expectancy during biblical times?

I think it is one of the psalms "Seventy is the sum of our years, or eighty if we are strong." Average lifespan was something like 43-45 right up to the mid 1800's. The average length of marriage in the mid 1800's was 13 years - one or the other would die. This also explains the far lower divorce rate. With the much longer lifespan today and the population explosion it is a FACT that of ALL the people who have EVER lived on the face of the globe, 51% are alive right now.