Motion capture

Dawn of the Planet of the Apes uses motion capture to record the movements and facial expressions of actors, and this data is used to animate the apes. How well does it work? "I think Andy Serkis moves in a very realistic way [as a chimp]. His portrayal of Caesar is wonderful," says Cat Hobaiter, who researches the evolution of communication and social behaviour at the University of St Andrews, in particular through studies of wild chimpanzees. "I'm 100% behind motion capture, especially with apes.”

Chimp and human facial expressions do not always correspond, however. Human smiles are equivalent to chimps' "bared-teeth" expression, while our disgust face seems to be exclusive to humans.

According to primate expression expert Bridget Waller from the University of Portsmouth, motion capture, “makes their faces a little bit too human-like", exhibiting greater subtlety of expression than is seen in other apes. "We haven't found much evidence that chimpanzees 'frown'," she says, "but humans frown all the time. Chimpanzee expressions seem closest to us, but they produce lots of hoot faces and pouts, which we don't!”

There is certainly lots of hooting in Dawn.

Caesar's family

Screenwriters, Rick Jaffa and Amanda Silver, have given Caesar a gorilla-style family, rather than the usual chimp arrangement of a mother with the offspring of several different fathers. Behavioural psychologist David Geary from the University of Missouri, has put forward the theory that when the ancestors of humans and chimps split from ancestral gorillas 7m years ago, they retained gorilla breeding patterns (a dominant male with one or more breeding females). But when the chimp and human lineages split 2m years later, chimps evolved more promiscuous breeding patterns while our lineage retained the gorilla-style family.

So, in terms of his family, Caesar is reverting to his gorilla ancestry. According to Geary, this makes him more human-like. “I wonder if the writers went with the chimp-centric view, but then defaulted to what seems more natural to them – a gorilla-type family?" says Geary. "Would men like to live their lives with other men, constantly fighting for dominance and sexual access to females who go into oestrous once every five years … or have a family? Most men prefer a family, which is not what you'd expect with a deep, chimp-like ancestry."

An angry bonobo

Jaffa and Silver have created a male bonobo character called Koba. Bonobos have only been understood to be a gracile species of chimp for the past 20 years, and they didn’t feature in the original 1968 Planet of the Apes movie.

Bonobos split from chimps two million years ago and have evolved a more "juvenile" behaviour as grownups. Adult bonobo males prefer to hang out with mum, for example, and they do not create male coalitions. Instead, they use intense, non-reproductive sexual behaviour to diffuse tension.

Koba doesn’t fit this description – he is aggressive and part of Caesar's primate army. However, this could easily be attributed to his very unnatural origins. “Any animal, including a human, socially isolated, caged, receiving multiple invasive procedures, is not going to be a normally developing individual, an angry bonobo wouldn't be outside the realms of possibility,” says Hobaiter.

Koba exacts revenge on the humans who hurt him. I asked bonobo expert Prof Frans de Waal from Emory University in Atlanta, Georgia, if this was plausible. “Yes, apes have excellent memories, and do have a tendency for revenge, so this isn't too far-fetched."

Walking on two legs

The apes in Dawn spend a lot of the film upright, on two legs, which is not typical behaviour – at least where chimps and gorillas are concerned. "I think the easiest species to mimic would be the bonobo which has relatively long legs," says de Waal. "They walk bipedally in a very human-like manner."

By contrast, chimps and gorillas have a highly characteristic gait involving both their legs and arms. "Both male chimps and gorillas have beautiful broad shoulders they show off when they walk, their arms are part of the walking, their shoulders moving more impressively than in our species," says de Waal. "I often think our épaulettes stem from this! When apes are depicted mostly bipedally this shoulder play is lost.”

Bipedal apes had shock value in the 1968 film. However, field studies have since revealed that all species do occasionally use bipedal locomotion and research suggests it’s no more costly in energy terms for chimps to walk upright than on all fours.

Humans have longer legs relative to their overall body size compared with other apes, which makes it harder for tall actors to "ape" apes. Anthropologist Professor Leslie Aiello, president of the Wenner-Gren Foundation for Anthropological Research in New York, told me: “We’re probably stronger than chimps in the leg muscles, our large buttocks and big calves facilitate human bipedalism."

Even so, she describes Serkis’s transformation into a chimp as "amazing”.

Sign language and gestures

Caesar teaches sign-language to the other apes, which may seem far-fetched, but a chimp that had been taught American sign language in captivity was observed to teach correct sign language to chimps in the wild after being rehabilitated to Africa in the 1970s.

Many human and chimp gestures are interchangeable, such as begging, arm outstretched, palm upward – a gesture used in Dawn.

Nonverbal communication is a fundamental characteristic of both humans and other great apes. Hobaiter has discovered that chimps can “talk” to each other by gesturing, but in Dawn different ape species communicate with each other. Is that even possible? “There’s a lot of overlap in gestural repertoires, so theoretically, yes."

Talking

The protein product of the human FOXP2 gene, which is indirectly responsible for our vocal folds, tongue and soft palate control, is only two amino acids different from the chimp FOXP2. It's the only gene so far implicated in human speech. Margaret Clegg, a specialist in the anatomy of speech at London's Natural History Museum, explains that fine motor control is needed to speak and we have finer control of the vocal tract and diaphragm than chimps.

"We developed motor control to make complex tools and co-opted this for improving our speech," she says. "The two brain areas controlling these movements are next to each other. I’m sure you’ve noticed when you make difficult hand movements you move your mouth – think of a child learning to write.”

If Caesar had fine motor control could he talk? “In the film the apes have been genetically altered and Caesar has been taught sign language, so it would be possible.”

So how convincing is Caesar’s speech, as a fictional talking chimp? “His syntax seems to be similar to that used by signing chimps and how Caesar sounds is plausible given the chimp's vocal tract.”

Babysitting by males

At one point in the movie, Caesar does some babysitting, which would be very unlikely to happen in nature. “Fatherhood is not a chimp or bonobo thing. The males are at best protective, at worst [in the case of chimps] infanticidal. The carrying and care is for mothers."

Males are not completely indifferent to youngsters, however. "Exceptional males adopt orphans. If the mother is out of the picture, males may carry juveniles … and sometimes are caring for several years,” says de Waal.

A chimp with a heart

Caesar has a caring personality. On the face of it this might seem like Hollywood sentimentality, but chimps and humans have personality traits in common such as "agreeableness", extroversion and conscientiousness. The same genes may be involved in determining these traits in both humans and chimps.

Chimpanzee males, like human males, vary in their social skills. Chimps expressing the RS3 gene (which is essential for language in humans) are more socially skilled with higher status. The same gene is associated with variability in social behaviour in humans. Only one third of male chimps have the allele, but it looks as though Caesar is one of them.

Caesar fights to maintain his ape community. This is also perfectly plausible, as research on the chimp Y chromosome has revealed that chimps develop stable communities, some of which are thousands of years old.

Verdict

Dawn may be science fiction, but pure fantasy it is not.

Dawn of the Planet of the Apes is on release in the UK from Thursday