Life has its ups and downs, but for the most part we prefer it over the alternative. We may choose to fill our lives with things that are good for us — veggies, exercise, sex — or things that harm us, like drugs, inactivity, and loads of red meat. Some choices will obviously harm your chances of living longer, but some are a little more subtle. Most everyone would jump on a secret tip for prolonging life, though.

Sounds a bit greedy, considering we’re already living longer than ever. Two hundred years ago, the life expectancy in almost every country in the world wasn’t breaking 40, with some African countries coming in at a horrifyingly low 25. Now the global average is 71 years old, and expectancy in some countries has even reached over 80. Medicine and diet have contributed most heavily to this rise, but how far can we really push it? Is there a biological limit to how long we can live?

To understand this, researchers have to look at aging itself, rather than the myriad of ailments that can kill us. Some scientists believe it’s caused by our DNA breaking down after time, becoming more and more susceptible to mutations. Some think the key to the process lies in our diet or in our core temperature.

Take a look at the video to see what science has to say about living longer, and what researchers think toast could tell us about why we get old.