New research reveals longevity gains slowing, life expectancy of 100 unlikely

Genetics required. Natural evolution has zero interest in old people, so there has been no evolutionary pressure to extend lifespan. Possibly even the opposite.

We could apply that pressure, either through selective breeding over generations, or through direct genetic modification. Maybe we aren't quite there yet, but it won't be long.

Experiments on insects with selective breeding have easily tripled lifespans. How well that would transfer to mammals is hard to say, but a substantial increase is certainly possible.

Mick Jagger had his most recent son at the age of 73. Today, that's an anomaly, but historically, older men fathering children was not at all uncommon (73 would probably be an outlier, but successful men were fathering children well past the age when women can no longer bear children). That would exert significant evolutionary pressure for men to have longer lifespans.