In the Origin of Species, Charles Darwin presented that species evolved to best suit their environments. Endurance exercise was central to the extensive hunting and gathering of early human ancestors. To support prolonged exercise in the heat, the cardiovascular system must work hard to keep the body cool and to provide blood to exercising muscles and the brain. Thus, having a cardiovascular system that supports endurance activity in the heat would have been beneficial to early humans. In stark contrast, humans in postindustrialized societies live in temperature-controlled, sedentary environments. Cardiovascular disease is the leading cause of death worldwide; however, it is extremely rare in preindustrialized societies, such as modern hunter-gatherer and subsistence farming populations. This project aims to investigate cardiovascular aging from an evolutionary lens. Over the next three years, we will compare vascular structure and function in semi-wild chimpanzees, hunter gatherers in Tanzania, subsistence farmers in Mexico, and sedentary residents of British Columbia. The results will help us to understand what normal cardiovascular aging in humans is.