Often considered an inevitable part of male aging, benign prostatic hyperplasia (BPH) is the most common non-life threatening disease to affect men in Western populations.  We examine age-related change in prostate size and BPH risk and related serum biomarkers among the Tsimane Amerindians of the Bolivian Amazon who live a traditional lifestyle of hunting and small-scale horticulture.  The Tsimane are a critical case study for understanding the etiology of BPH as they have significantly lower levels of testosterone than age matched US males, as well as low levels of obesity and metabolic syndrome, factors associated with BPH in previous research.  Ultrasounds were conducted on 348 men aged 28-89 years (median age 56 years). Testosterone, PSA, and HbA1c were examined in relationship to prostate size and BPH.  Tsimane have less than half of the BPH prevalence experienced by US men, and age-adjusted prostate volumes 62.6% smaller. While Tsimane have low levels of testosterone and subclinical levels of metabolic syndrome compared to US men, Tsimane with high testosterone were more likely to experience BPH, as were those with higher HbA1c.  Overall, these data suggest that BPH may not have been an inevitable part of male aging throughout human evolutionary history.