The vast majority of the longevity gains have come from our having clean water, sewer systems, clean and abundant food. The biggest obstacle to advancing average longevity has long been infant and childhood mortality and failure to develop properly. For most of human history getting kids to puberty was the biggest trick. Young adults, even today, tend to fall to violence, accident and suicide. It was fairly common for wealthy Romans 1200 years ago to get into their sixties, and occasionally seventies.

We lost most of all that for better than a thousand years after the Roman empire disintegrated and the western world had its dark ages.

In terms of actual contribution to longevity medical science hasn't added a whole lot. The big improvement hasn't been so much longevity but quality of life.