Indeed, testosterone levels in men have been declining for thousands of years. But we’ve seen massive drops in the past 50 years — a timeframe that coincides with the introduction of synthetic estrogens in our environment. While that’s just a correlation and it doesn’t imply causation, I choose to err on the side of caution. Based on past experience (think lead paint), it’s usually only a matter of time until we’ve figured out that man-made chemicals aren’t good for us.  Plus, there is plenty of scientific evidence (as mentioned throughout this article) that xenoestrogens negatively impact the reproductive health in animals and humans alike. Abnormally low levels of the sex hormone testosterone are merely one of the indicators that our reproductive system isn’t functioning optimally.