What are the current biological limits on our human life span, or our human “youth span,” as you call it—the time that we’re able to live as young, vibrant, reproducing individuals?

Foddy: The sky is sort of the limit there. There won’t be a magic pill that gives us infinite youth, but over time there will probably be different technologies that allow you a few extra years of youth. We think of aging as being a unitary thing, but it’s made up of hundreds of different processes. So, one of the different things we think about, for example, is dementia, the state where your brain sort of wastes away. Now, if we discover a way of reversing that process, or slowing that process, that would be one dimension where we no longer age, where our minds will stay youthful for longer. It’s also possible that we might be able to find a way of stopping people’s muscles from wasting away as they get older.

Nothing is going to be super dramatic, but there will be a point where you’ll look back a hundred years and notice that people used to get really kind of feeble and after awhile they weren’t capable of really thinking or processing information anymore, and they had to go into a home and they had to be looked after and nursed for a time. And that will seem very old-fashioned and very barbaric, but I very much doubt it will happen at a moment in time where we suddenly realize that some magic pill has exponentially extended our youth. Part of that’s because we’re not exactly clear what aging is. We’ve identified a whole range of processes, but there ere still a whole lot of arguments in the scientific community about what is really responsible for aging, and which of the processes are subsidiary to other processes.