Death by Design.
Fortunately for me and my fellow human beings, we don't go up in flames at thirty. We may not get the two hundred years or more that some organisms enjoy, but for a mid-sized mammal, people get a pretty good deal when it comes to time. All of us are familiar with how short a life our companion animals have in comparison. At seventeen, my son was still a kid, but at the same age his poor Golden Retriever was down to her last days. Many larger animals, a cow for example, rarely live to twenty even if no one is eying them for steaks, and plenty of people-sized creatures (kangaroos, for one) don't even get a decade.
Still, despite all those charts of average lifespan over time, our potential for extended life isn't a new invention. Our closest living relatives, chimpanzees, live only 30-40 years out in the forest, but are capable of living 60 years or longer when removed from the stress and resource restrictions of the wild. Humans seem to be right in line with other primates of similar size. The biggest threat to maximizing the potential of many human beings today is not the wear and tear of fending for themselves, but the ease and abundance that causes us to eat, drink, and merry ourselves into an early grave (says the guy who downed a s'mores pop-tart and three cups of coffee while typing this article).