In early film, it was eugenics; in the Fifties and Sixties, radiation; in the Seventies and Eighties, cyborg enhancement. For the last two decades, the secret behind most of our onscreen superhumans, mutants and monsters has been genetic engineering. But can this fast-developing science really create the kind of abilities we see onscreen, and how much of it is possible with today's technology?
Although much has been made of the mapping of the human genome, the fact is that we still don't know what most of it does. Genes for enhancing certain core abilities are, however, quite well mapped, for two reasons. The first is that, just like in the movies, the military has an interest in them. The second is that the regulatory bodies that deal with athletics strive to keep track of what makes some people excel at sport, so they can make it harder to cheat. It is rumoured that there are groups in both these industries looking for ways to alter genes (which can be done in adulthood, at least in some cases) to create superhuman individuals like the hero of The Bourne Legacy.
Jeremy Renner's fugitive agent, Aaron Cross, is not in an ideal situation by anybody's standards. In gaining his special abilities, he has been made dependent on medication, without which they cannot be sustained. Two significant changes have been made to his body. Firstly, his intellect has been boosted by interfering with a genetic trigger that makes it easier for him to develop fresh connections between the neurons in his brain. Secondly, he has gained the ability to absorb protein more efficiently, improving his ability to build muscle tissue and to recover from injury.
The science behind Cross' enhancement is fairly realistic, with the genetic changes effected through the use of a 'tame' virus. The real problem with this type of change is its potential for side effects. Neurological connections are regulated differently in different parts of the brain, but by and large the problem with building them more quickly is that the chance of inappropriate connections being made escalates, so people begin to make unlikely associations and store memories they really don't need. Memory boosting drugs, which trigger a similar process, seem from tests to be useful if combined with focused mental work (such as studying for an exam), but their helpfulness in other situations is more doubtful. Meanwhile, the protein adaptation, a rather roundabout way of improving muscle quality, could easily lead to problems. Too much protein in the body can put a strain on the liver and is also thought to damage the kidneys.
As with Alice (Milla Jovovich) in the Resident Evil films, or Saoirse Ronan's Hanna, Cross' main physical advantages are increased speed and strength. At least some of the genetic routes to achieving this are quite well understood. Most of the world's best sprinters have a genetic mutation that gives them a high proportion of type IIx muscle fibres, enabling them to make amazing bursts of speed. The problem is that these fibres also tire quickly, so for superpowers that last more than a couple of minutes, you also need to have a lot of them. Fortunately, there's also a known mutation that suppresses the hormone which normally limits muscle growth. The catch? The super-powered muscles we might build today would be big and obvious, like in comic books - they couldn't fit within Jovovich's slender silhouette.
Big muscles also need a lot of fuel, probably the reason they haven't evolved to be more common. Heroes who spend extensive periods on the run with no time to snack would soon run into problems. But there are alternative ways to enhance abilities that, though less dramatic, could provide a significant advantage over the average person.
Most people's muscles are capable of working harder and faster than they usually do - it's just that they get worn out. One way around this is to fuel them more efficiently. Research into diabetes is gradually revealing the genetic secrets to maintaining good blood sugar levels, though diet will always be a big factor there. But still more important than this is how much oxygen blood can access. There are several known mutations that affect this, some of which flourish in particular populations, creating groups of people who can do things most of us would struggle with, such as leading active lives at high altitudes where the air is thin. Tibetan people carry a unique gene that gives them wider blood vessels, enabling blood to carry oxygen around the body more efficiently. It's entirely possible that we'll be able to engineer changes like this within a few years, so they would make a good explanation for the increased stamina seen in characters like Hanna.
The other thing to bear in mind about bodies is that they have evolved to work as complete systems. Altering one part inevitably has an impact on others. The Dark Knight Rises sees Batman confronted with that fact that no amount of muscle-aiding technology can keep jumping off buildings from damaging his bones. Understanding the genetics of bone growth is still at a very early stage, and although there are interesting new biotechnological materials being used to replace bones in some cases, this is an area that film has yet to explore.
Although neurological enhancement of the sort Cross undergoes could be problematic, other, more specific types of brain enhancement are comfortably within the realms of possibility - and not just for humans. In Rise Of The Planet Of The Apes, a drug designed to treat Alzheimer's disease has the effect of boosting intelligence (as it does for sharks in Deep Blue Sea) and also of giving a chimpanzee the power of speech. Whilst little in Alzheimer's research relates to general intelligence, making this rather unlikely, we have an increasingly sophisticated understanding of the genes underlying our ability to speak, and it's possible that this could one day result in apes who are able to talk. Charlton Heston probably wouldn't have approved.
Genetically modified animals feature in a number of films. The birds enhanced so they can work as spies in The Hunger Games might not need much work, as it's becoming increasingly apparent that some species have a natural ability with language and parrots have now shown the ability to make inferences based on observations. Genetic experiments have already been conducted with birdsong, paving the way for work on speech.
Whilst it's unlikely that we'll ever be able to genetically engineer a spider whose bite can grant Spider-Man style powers, mapping the genes behind the production of spider silk has been one of the science's greatest triumphs. Spider silk is an amazingly strong, resilient material with all sorts of possible uses. Arachnids produce it in such small quantities that harvesting it from them would never be practical, but genetically engineered goats can now produce it in their mammary glands so that it can be extracted in useful quantities in their milk. This means it's entirely possible that we could one day enable humans to produce it. Even if it could be produced from the hands in a quantity good enough for swinging on, though, there would be difficulties that Peter Parker never had to deal with. Producing silk is exhausting for spiders, with many eating their old webs to recover some of the energy. A silk-spinning human would need to eat several thousand extra calories a day in order to cope.
All these complications mean genetic engineering is unlikely to be the easy route to super powers that cinema likes to suggest. A more realistic use of it is that seen in Gattaca, where it is principally about getting rid of problems like "premature baldness, myopia, alcoholism and addictive susceptibility, propensity for violence and obesity." Though Gattaca raises concerns about the possibility of genetic enhancement changing the way we perceive and value individuals, it also implies that there's a lot to be said for maximising our existing potential. For most people, good health is ultimately a bigger deal than super strength, and physical perfection is recognised as another of Hollywood's illusions.