What I noticed watching that was: William Shatner looks a lot younger than 51 years old in that film, yet that is precisely how old he was at the time the movie was released (I guess he was probably 50 when it was filmed). I would have guessed he was, maybe, 42... 43... or so. So, he was, biologically, about 7 or 8 years younger than his true, chronological age. He is now almost 90 years old (88, to be precise), and certainly doesn't look it.
In fact, he's still starring in movies! He looks decent for an almost-90-year-old:https://news.yahoo.c...-141846489.html
I'd guess he was about 77 or 78 years old in that picture; so, he looks 10 years younger.
He must have some pretty strong SIRtuin genes!