This summer, 68-yearold Harrison Ford will be mixing it up with Old West-invading extraterrestrials in Cowboys & Aliens. Next month, 67-year-old Robert De Niro will star in the action thriller Limitless. When The Expendables II opens in 2012, the combined age of its top five prospective stars, God willing, will be 291 years.

The landscape of recent motion pictures, in particular Manly Movies, looks increasingly like the last days of the dinosaurs.

The performers are greying (never literally, of course), the shooting and editing are getting tighter (to suggest, rather than capture, physical exertion) and if one were to compare the future of Hollywood he-men to say, The Terminator, there would be few replacement parts in the warehouse. Who's coming along to fill the shoes of Clint Eastwood, Sylvester Stallone, Arnold Schwarzenegger, Bruce Willis -or even Liam Neeson, who opens Friday in the highbrow espionage thriller Unknown? Orlando Bloom? Yikes.

"There's Leonardo Di-Caprio, Tom Hardy is becoming a movie star, Christian Bale, a few others," said Unknown director Jaume Collet-Serra, who may be obliged to be pro-Neeson but still has a point. "It's hard to find an actor who has the physicality, the good looks, the charm all on top of being an amazing actor -that's the most important thing, but not always what people pay attention to."

It's largely a question of gravity. And money: The older stars still draw crowds. "They do," said Paul Dergarabedian, who tracks box office for the industry at Hollywood.com. "If the movie is cast properly, it doesn't matter if the actors are younger or older, as long as they can sell it on screen."

He said that while plausibility is important, acknowledging the age differential has become a tactic, too. "I think Red was a great example of a film that's taking the concept of the aging action star and putting it front and centre," he said, citing the recent comedy thriller starring Willis, Helen Mirren, Morgan Freeman and John Malkovich. "Sort of like The Expendables, which kind of said 'if one older action star can't bring people in, maybe five of them can.' "

That film starred Stallone, Jason Statham, Jet Li, Dolph Lundgren, Steve Austin and Mickey Rourke (plus an uncredited Willis and Schwarzenegger), cost $80 million, and has thus far made $274 million worldwide.

Liam Neeson is not quite in that action-figureinspiring groove. He's idiosyncratic -"an 'edge case' they call it in cyberworld," said Tim Appelo of The Hollywood Reporter, who writes its Oscar blog, The Race. "He's not typical. He got the Schindler part precisely because he had no firm persona," Appelo said, referring to Steven Spielberg's Schindler's List.

"Spielberg wanted an actor who brought zero prior baggage to the part, so he could be completely mysterious and Schindler alone. There's a kind of heroic remoteness to Neeson."

That remote heroism certainly benefits Neeson's performance as Unknown's Dr. Martin Harris, who arrives in Berlin for a biotech conference, is saved from a watery car wreck by his plucky taxi driver (Diane Kruger) and, after a brief hospitalization, returns to a wife (January Jones) who doesn't seem to know who he is. The plot is part Hitchcock, the action owes something to Bourne, and the star is 58 years old.

Which makes him younger than some of these guys (Schwarzenegger, Stallone and Robert De Niro are in their 60s; Eastwood, 80). But old enough to give pause when he's cast -visa-vis the hallowed Hollywood tradition -opposite actresses as young as Jones, 33, or Kruger, 34.

"I find that very strange at times," Kruger said with a laugh.

"And it was very important to Liam and myself -and I have to give credit to the studio -that there was no real romance between those characters. It's more like Natalie Portman and Jean Reno (in The Professional), two people who come together at one point in their life."

She agreed, however, that it would be tough to find younger actors who could play a character with as much psychic baggage as Martin Harris.

"They could play it," she said, "but I think it would be a different movie, a lighter movie. Liam brings experience; he's of a certain age, but he doesn't even have to say anything -every line in his face gives a depth to the film. He's not the 25-year-old punk-rock hot guy -not that I don't like watching those boys. But with Liam, you know there's always something underlying the story you're about to watch."

Who from the younger ranks is going to take over as the movie hero? "I used to think Jason Statham," Dergarabedian said, "but he's not that young anymore. Ben Foster? The actor has to be believable doing the things he's doing on screen. Matt Damon has been very credible in the Bourne series and Daniel Craig as Bond, but they're both a little older, too. Hard to think of someone in their 20s?

There might be that guy from G.I. Joe. What's his name?"

Exactly.