and re-evaluates the evidence presented in the widely-cited 2017 meta-analysis by
and colleagues.
‘Sperm counts among men globally, and especially from “Western” countries, are in decline, leading to apocalyptic claims about the possible extinction of the human species. However, research suggests that there is no need to panic too fast with the apparent trends of declining human sperm count as the biovariability offers a more promising framework of human existence than does sperm decline.’
An alternative explanation of sperm count trends in human populations as provided by the study claims that sperm count varies within a wide range, much of which can be considered non-pathological and species-typical, and that above a critical threshold, more is not necessarily an indicator of better health or higher probability of fertility relative to less. The study team term this as the Sperm Count Biovariability hypothesis.
“By proposing an alternative approach to sperm count data, we aim to contribute to the burgeoning discussion among reproductive health scientists and other researchers and clinicians about men’s health,” says the lead author Boulicault.
The Sperm Count Biovariability
The Harvard researchers argue that claims of recent and impending dramatic declines in human sperm counts are based on several scientifically and ethically problematic assumptions that include the following:
- Claims about precipitous sperm decline assume that sperm counts in Anglophone developed nations of the 1970s constitute the species optimum.
- The assumption that male fertility scales proportionately with sperm count is unsupported by any available evidence. Declining sperm counts do not predict declining fertility.
- The geographical and historical patterns of average population sperm counts do not support the proposed causal mechanism for lower sperm counts due to the exposure to environmental endocrine-disrupting chemicals.
- The major 2017 meta-analysis of sperm decline studies that uses two labeled categories ¡V “Western” and “Other” in analyzing sperm counts, stands scientifically unsound and embeds unethical racist and colonial assumptions in the study design.
- The diversity across rural and urban locations within nations is obscure by these statistical aggregations and its disguises the fact that there is very limited data on individuals’ sperm counts in countries categorized as “Other.”
“Researchers must take care to weigh hypotheses against alternatives and consider the language and narrative frames in which they present their work. In addition to its explanatory virtues, we argue that biovariability offers a more promising framework than does “sperm decline” for attending to these imperatives,” concludes the paper.
Source: Medindia
