Your adult race destiny may be determined at birth. Ultra-endurance events have surged in popularity, with more than 150,000 North Americans racing ultramarathons (a distance longer than the standard 26.2-mile marathon) last year. And while these hardcore events can prematurely age vital parts of the body, one factor may shape how the body responds to extreme endurance exercise long before adulthood. A biological limit that surfaces in ultra-endurance events may be determined long before adulthood at birth. Michael Nigro for NY Post Scientists believe humans were made to run long distances , citing evolution during the hunter-gatherer days. However, endurance events place a large amount of strain on the kidneys, which could negatively affect their filtration system and lead to cellular damage. A study published in Frontiers in Ecology and Evolution  has now found a potential link between birth weight and kidney health in ultramarathon athletes.…