Episode Details

https://astralcodexten.substack.com/p/declining-sperm-count-much-more-than 

Is Sperm Count Declining?

People say it is.

Levine et al 2017 looks at 185 studies of 42935 men between 1973 and 2011, and concludes that average sperm count declined from 99 million sperm/ml at the beginning of the period to 47 million today.

Levine et al 2022 expands the previous analysis to 223 studies and 57,168 men, including research from the developing world. It finds about the same thing.

The “et al” includes Dr. Shanna Swan, a professor of public health who has taken the results public in the ominously-named Count Down: How Our Modern World Is Altering Male and Female Reproductive Development, Threatening Sperm Counts, and Imperiling the Future of the Human Race.

Is Declining Sperm Count Really "Imperiling The Future Of The Human Race”?

Swan’s point is that if sperm counts get too low, presumably it will be hard to have babies (though IVF should still work).

How long do we have?

This graph (source) shows pregnancy rate by sperm count per artificial insemination cycle. It seems to plateau around 30 million.

An average ejaculation is 3 ml, so total sperm count is 3x sperm/ml. Since sperm/ml has