Is the human race on the verge of extinction? That’s the jaw-dropping claim made in Professor Shanna Swan’s new book ‘Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race’. According to the book, sperm counts have dropped almost 60% since 1973 and suggests that they could reach zero by 2045, which would mean no more reproduction and no more babies.

This is a worrying discovery, particularly as one of the central drivers of this trend is modernity itself; Swann argues that chemicals, ranging from ATM receipts to Tupperware plastic, in the modern environment are altering —and endangering — human sexual development, and is getting worse by the year.

Even if you find this argument a little too extreme (as UnHerd columnist Tom Chivers does), Prof Swan is certainly worth listening to. Having devoted over 20 years of her career to the study of sperm, the epidemiologist is about as well-credentialed as they come and has made a fascinating contribution to the debate. We thank Prof Swan for her time and hope you enjoy the discussion. Key quotes below:

On plummeting sperm count:

What we found was that sperm count had to climb dramatically over the preceding 40 years, and was at a point where nearly half of men would be entering that range of sperm count, which is associated with sub-fertility at least. We didn’t see any indication that the slope of that line had levelled off, so that when we looked at the data restricting it to the past 30 years, 20 years, 10 years, you might hope that it would be flattening out. But we didn’t see any indication of that, which is alarming, because if it were to continue on its present course — that’s a difficult thing to project — but just mathematically, if you’ve extended the line, it does hit zero in 2045. So that’s the median sperm count, that means half of men would have no sperm.

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