I think this underestimates our most primal of instincts, survival. Those people who died at 48 a century ago had no less want or determination to live longer, than did those who die today at 78. In those times, their options were extremely limited, so as a culture, our norms prepared them better to accept death. Nowadays we have many options, and modern medicine has become the ultimate tool of our survival. Yet another profound ability that separates us from other animals.
If you know how to recognize good interaction and visual design, go with your gut instincts. Also the biggest factor in hiring anyone is whether or not you can see working with them.
I've found some of my best interaction designers in juniors, fresh out of college, with crappy portfolios, but where I could see potential in them, and them wanting to learn.
I've also found senior interaction designers, with portfolio's to die for, crazy good experience, and have found them to be not willing to take feedback or with collaboratively with other designers and developers.
You never can tell. My experience has been that it's better to find someone stronger on visual design, information design, and aesthetics and that the Human Factors and usability stuff can be mostly taught quickly. It's impossible to do it the other way around.
I've been hiring and training interaction designers for over 6 years and have a UX agency, so I've become pretty adept at going with my gut feeling and mentoring young interaction designers.