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Chimps Don't Cry: Behind the Science of 'Dawn of the Planet of the Apes'

Image: Dawn of the Planet of the Apes - 2014.

Dawn of the Planet of the Apes - 2014.Rex Features via AP

Never in recorded history has an ape fired a machine gun, let alone two machine guns while riding a horse through a wall of fire.

That is exactly what happens in “Dawn of the Planet of the Apes,” which hits theaters on Friday. (Warning: mild spoilers ahead). Sure, a primate doing its best "Rambo" impression isn't the most realistic scenario in the world, but not everything in the movie is bananas.

"We tried to ground everything in reality as much as possible, but there are certain things, like the fact that they can’t speak, that we had to jettison for the drama of the story," Matt Reeves, director of "Dawn of the Planet of the Apes," told NBC News.

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So which parts of the movie are based on science and which are just fantasy? Reeves and famous primatologist Frans de Waal, author of "The Bonobo and the Atheist: In Search of Humanism Among the Primates," broke it down.

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Armed to the Teeth ... Also, With Teeth

In the movie, the primates are armed with everything from menacing spears to automatic rifles. A chimpanzee using a gun is far-fetched. A spear? It's actually something that chimps use — well, on a smaller scale. Instead of huge weapons meant for taking down humans, they are more like sharpened sticks meant for stabbing bush babies — tiny, adorable primates that chimpanzees love to eat.

Chimps also regularly throw things like rocks and feces, de Waal said. Their bodies, however, are probably their most potent weapon.

"Their arm strength is incredible, they have feet that act like arms and they have teeth," de Waal said. "I would say 10 men could not hold down a chimp if it did not want to be held down."

Let's Talk About a Lack of Sex

There is a reason "Dawn of the Planet of the Apes" is rated PG-13. In the movie, the apes sit around looking stoic, weighing the costs and benefits of war. In real life, there would be a lot of monkey business going on.

The apes would be engaging in way more copulation, de Waal said, which brings up another problem: None of the primates in the movie have visible genitals.

"They are a bit like teddy bears or something," de Waal said.

"He is not just a bonobo, he is a bonobo that was kept captive by humans and experimented on, which is kind of a horrific thing if you imagine yourself as that ape."

Not only that, but male chimps usually make up after a challenge to an alpha male's dominance — something that happens almost daily — with more than just a touch of hands like in the film. A kiss on the lips is common, or a hand placed in the dominant chimp's mouth.

Bonobos take it one step further by resolving conflicts with full-on sexual contact, which is why the chimpanzee cousins are known as the "hippies of the primate world." Koba, the film's villain, is a bonobo. So why does he practice violence instead of free love?

"He is not just a bonobo, he is a bonobo that was kept captive by humans and experimented on, which is kind of a horrific thing if you imagine yourself as that ape," Reeves said.

Hiyo Caesar, Away!

Obviously, apes don't ride horses. But Reeves wanted references for every kind of movement, so he hired stuntmen who knew parkour and had WETA (the special-effects firm that became famous for the "Lord of the Rings" movies) create some simulations to make it look as natural as possible.

He also gave Andy Serkis (who plays Caesar, the protagonist) and the other actors forearm extensions to make them move like apes, making for some eerily realistic CGI creations in the final cut of the movie.

"It seemed to me that would be the most uncanny experience — to see chimps that were acting like chimps but were expressive in a way that was very human," Reeves said.

Real Chimps Don't Cry

In the movie, Caesar is basically father of the year, doing everything he can to save his family. In nature, he would probably be a deadbeat dad.

"Male chimps don’t really know who their offspring are and they don’t necessarily care," de Waal said.

He probably would not shed any tears, either. Physically, humans can do two things that chimpanzees can't: blush and cry. In the end, Reeves decided to let the apes ditch the law of the jungle and get in touch with their sensitive sides.

"I tried to make as realistic of a fantasy as possible, but at the end of the day, it’s still a fantasy," de Waal said. "To look at the animals in this story is really to look at our own nature, and if we took out the unrealistic aspects of their characters entirely, it would be much harder to explore their emotions."

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