Human zero sperm count in the next generation: Really? What are the facts?
The aspect of declining sperm count has been debated over many decades and is very controversial. Recently Dr Haqgai Levine presented a paper at the 13th International Symposium on Spermatology in Stockholm that sperm numbers are declining and represent a crisis in terms of humans potentially becoming extinct as referenced by Daniel Halpern:
Are we as scientists/spermatologists/andrologists in agreement with the presentation of Haggai Levine at 13th ISS and the above scary webpage by Daniel Noah Halpern? Is it too selective or what are the alternatives? But before we venture into that I am in total agreement with Lars Bjorndahl, reputable clinical spermatologists and organizer of above conference, that we “respect epidemiological studies but we should remember that mathematical correlations don’t prove that there is a causative relation”!
The majority of reputable spermatologists will not only reside with this opinion but question the basis of the Levine study particularly in terms of selection of countries/populations selected and the socio-economic aspects related to that. Yes, I respect the fact that in the Swan – Levine study selection of research papers/patients/donors was based on removing as many variables as possible but then ignoring the global picture is unacceptable (introducing more variables). The selection was predominantly based on a typically first world situation and ignoring the Southern hemisphere except for Australia (but Australia also represents first world). Dr Swan and Levine, what about the entire Africa, South America, China, India and many other countries globally? Many examples will suffice. The average number of children per family in Uganda in 2018 is 5. Surely if there was a decline in sperm numbers as they suggest one would expect less children per family and a decline in population growth! But then there are many more examples of high fertility elsewhere in the world. Also the decline from six children per family in the 1990’s in Kenya to much lower numbers currently has to do with very good family planning in Kenya particularly in the rural areas.
Another serious weakness of the Levine presentation is that they use one sperm parameter out of a multitude of important possibilities to define dooms day. In the last decade sperm quality assessment has increasingly shifted to sperm functionality and away from just the routine WHO semen parameters. There may be lower sperm concentration particularly in Central Europe but sperm functionality as measured by the percentage of rapid sperm or the ability to become hyperactivated are totally ignored in the Levine study. Furthermore, David Mortimer, at the above conference has pertinently indicated that in the older study’s methodology sperm concentration has been over estimated. So the Halpern reference of so called sperm concentration close to 100 million/mL in the 1970’s compared to 47 million/mL currently and that sperm concentration halved in 50 years is simply out of perspective. What is the basis of my argument? In South Africa, in the Cape Town area a reputable haemocytometer technique has been used with a positive displacement pipette and over 40 years’ (1960 to about 2000) sperm numbers have declined from about 49 to 47 million/m over this period (not significantly different) supporting the Mortimer idea of over-estimating in the past (white cell pipette dilution). Accordingly, the Halpern www is simply an exaggeration and out of perspective stating that sperm concentration was halved since the 1970’s as a general principle. A further bias in the Levine study is that the majority of studies are based on “patients” visiting infertility clinics and less on donors with apparently potentially fertile profile.
It must be made clear that several countries in Scandinavia and central Europe experience more deaths than births and accordingly a decrease in population growth. But to use the Lars Bjorndahl analogy, it will be wrong to equate this simply to a decline in sperm numbers but even if it represents a decline it potentially relates to many other socio-economic factors. Which factors? There are many. In modern Europe and also in many instances elsewhere, there is an increasing number of females that first select a career and then in the later thirties decide to start a family but then their fertility is compromised because of the poorer quality of the oocytes (late thirties). In a modern Europe with a competitive environment there are many stresses imposed on males and females leave alone life style factors such as obesity, smoking and many other factors such as older males and younger female partners. The fact is they become part of the sample showing a so called decline in sperm number. Yet it seems to be mainly socio-economic.
Van der Horst and Maree (2014) has furthermore shown that there is a natural decline in sperm quality in monogamous species and also largely relates to humans. This is an adaptation to a decrease in sperm competition. Just consider for a moment that in humans and gorillas sperm quality is poor when compared to the promiscuous species such as chimpanzees (in chimpanzees and also in monkeys the average sperm concentration may be 5 to 10 fold that of humans and percentage sperm motility considerably higher).
Finally, it is evident that due to chemical pollution (plastics) and environmental estrogens, and life style overall fertility will possibly be severely affected. Of course this needs our serious attention but I beg to relate a decline in sperm numbers for Homo sapiens as dooms day is just not credible. It is surely multi-factorial. Males with declining fertility potential and decline in sperm concentration need to be convinced to first change their life style. I believe in the next couple of generations we may be multiplying as humans to reach sustainable levels for Mother Earth with sensible family planning and optimizing IVF. But please, the evidence of zero sperm in the next generation and even well beyond is by all good scientific arguments not reasonable!!! There is a much bigger chance that human males may disappear in 2 million years because of the disappearance of the Y chromosome than ever reaching zero sperm count.
Yippee……my good friend Charlie Brown will still have sperm in 2 million years!
Prof Gerhard van der Horst (PhD, PhD)
Emeritus Professor, Medical Bioscience, Univ Western Cape, Bellville
Extra-ordinary Professor, Physiology Medical School and Department
of Animal Science, Stellenbosch University
Halpern, D. 2018. https://www.gq.com/story/sperm-count-zero.
Van der Horst, G and Maree, L. 2014. Sperm form and function in the absence of sperm competition. Mol. Reprod. Dev. 81, 204–216. doi:10.1002/MRD.22277