The Science of Avatar

³⁰ ANGELS AND DEMONS

Perhaps the single most complex element of the movie Avatar, both scientifically and mythologically, is the idea of the avatars themselves.

The avatars were originally created as a labour force adapted to conditions on Pandora, but proved too expensive for the purpose. Later, after pressure from the UN, scientists and the general public to establish fuller relations with the Na’vi, RDA changed the avatars’ mission; they became ambassadors for humanity among the Na’vi. Since this failed to have satisfactory outcomes the avatars have been redeployed for reconnaissance, field science and exploration—and, covertly, under Colonel Quaritch’s command, to gather military “intel” on the Na’vi. In future they could have other uses, such as supervisors if the Na’vi are ever made to labour in human mines…

The avatars look like Na’vi, more or less. Yet they are not Na’vi, and nor are they human. They are made things, grown in a tank from a mixture of human and Na’vi genetic material. In fine details they differ from the Na’vi: their human-like eyes, the number of their fingers.

And they are unlike Na’vi, and humans, in that they don’t have minds of their own. An avatar needs the consciousness of a “driver” to function.

As a driver, Jake Sully is joined to his avatar by a “psionic link.” Lying inert in his link tank, perhaps kilometres away, he can operate his avatar as if it were his own body. He sees and hears and feels through the avatar’s sense organs; his mind controls the avatar body’s movements. While he is linked to the avatar it is as if he is the avatar.

New technologies rarely find just one application. Aside from the application on Pandora, what else could you do with avatar technology? The ability to grow mindless bodies, including presumably fully human ones, itself offers possibilities, even without “driving” them. They could be used as banks of organs for donation, for instance, or test beds for medical advances, or they could be used to explore the tolerance of the body to various extremes, heat and cold, airlessness.

“Driven” avatar bodies could be used as soldiers in the battle-field, disposable cannon fodder controlled by trained operators from the safety of link tanks in bunkers far behind the lines. Avatars could also be used on such assignments as bomb disposal, or sent into hazardous environments such as future Chernobyls.

How about entertainment? You could stage fight-to-the-death gladiatorial contests with “nobody” getting hurt. And we can’t begin to discuss the opportunities for pornography in a book about a 12-rated movie!

All of this would depend only on the cost—as Jake says, the avatar programme has turned out to be “insanely expensive”—and on whether an avatar body really does have no mind of its own. You would have to be absolutely sure that it cannot feel, or grieve, no matter what you do to it, or make it do.

In the chapters that follow we will look at how an avatar could be built and operated. But avatars also carry an extraordinarily complicated mythological weight, a weight that surely shapes the Na’vi’s reaction to them. Remember, the warrior Tsu’tey accuses avatar-Jake of being “a demon in a false body.”

There have been many fictional portrayals of mind-links and mind-swaps before, from F. Anstey’s Vice Versa (1882) to the recent movie Freaky Friday. In the 1960s, the boy hero of Gerry Anderson’s TV puppet show Joe 90 became a special agent “thanks to a fabulous electronic device which can transfer the brain patterns of those who are the greatest experts in their field” (according to a publicity brochure of the time). Joe’s gadget, a limited precursor of the avatar link, was itself anticipated by the “Educator tapes” of James White’s many “Sector General” stories, and the idea has recently been revived in a more adult form in Joss Whedon’s TV series Dollhouse. The recent movie Surrogates saw an ageing Bruce Willis operate a young-looking robotic “avatar” of himself. But the concept has never been taken so far as in the movie Avatar.

And the concept has much deeper mythological roots.

To begin with, Tsu’tey is right: an avatar is a false body. It is a made creature: that is, made by humans, not by nature, or any god.

Avatars are like the golems of early Judaic legends, which were beings created from mud by rabbis who approached God closely enough to attain the power to create life. The most famous such story concerns the Golem of Prague, set in the sixteenth century. Golems crop up in popular culture, such as in the X-Files episode “Kaddish.” Typically a golem is a slave of its creator. And having been made by a mortal it is a lesser thing than any human, who is made by God. The Frankenstein monster is a descendant of the golem myth, the dead brought back to life through science.

But golems have minds. The avatars of the movie are like golems but without minds of their own: they are controlled by the consciousness of their human operators. As such the name “avatar” is apt. The word is used in computing to describe a user’s representation of herself in some computational world, a game or a shared space like Second Life. Thus Jake is the “user,” the avatar his representation in the world of the Na’vi. This usage of the word seems to date from the 1980s, and it was popularised in “cyberpunk” novels like Neal Stephenson’s Snow Crash (1992).

But the word “avatar” has much deeper roots. Ultimately it derives from the Hindu, from a word for “descent.” An avatar is a manifestation of a god on the Earth. This is not like the divinity of Christ in the Christian religion; through the Incarnation Christ was God made man, whereas a Hindu avatar is more literally a god walking the Earth. Perhaps an avatar is more like an angel of Christian, Jewish and Islamic traditions. Interestingly, avatars in Hinduism are often sent to Earth for a specific purpose, just as avatar-Grace is sent to educate the Na’vi, and avatar-Jake is sent to negotiate their evacuation from Hometree. And, incidentally, Hindu deities are often shown as blue-skinned, like the Na’vi in the movie.

The control of the avatars by minds outside their bodies is like demonic possession, in which a human is controlled by an outside force. So Tsu’tey is also correct to say that there is a “demon” inside that false body. In the Christian tradition, the Bible contains many references to demons being driven out of possessed people. But the oldest references in western culture appear to go back to the first civilisations; the Sumerians believed sickness was caused by possession by malevolent spirits. And shamanic cultures, like the Na’vi, often also believe in possession. Disease is caused by vengeful spirits, the spectres of animals or of wronged humans, that can be driven out by exorcism.

James Cameron’s avatars are thus a modern reworking of a whole set of very ancient mythic elements. And with such a background the reaction of the Na’vi to the avatars can only be complicated, depending on how they interpret the avatars in the precise traditions of their own culture. To the Na’vi, humans are “sky people,” tawtute, and the avatars “dreamwalkers,” uniltirantokx, bodies possessed by spirits from the sky. Maybe it’s no surprise that at the start of Jake’s adventure we learn that the avatars have been forbidden to come to the Omaticaya clan’s Hometree.

But how is an avatar body created in the first place?

³¹ A FALSE BODY

During Jake Sully’s trip out from Earth aboard Venture Star, his avatar is force-grown in an amnio tank for the specific purpose of hosting Jake’s consciousness (or rather his twin’s, who had an identical genetic profile).

The amnio tank is an extension of a technology used on Earth, a kind of artificial womb used to grow replacement organs and limbs, cloned animals, and sometimes cloned humans. It contains a suspension fluid with carefully monitored nutrients, growth stimulants and other materials. Alternatively a patient with serious injuries or organ failures—Jake Sully, perhaps, if Quaritch had fulfilled his promise of a cure for spinal injury—can be placed in a “cellular rebuilder,” a modified amnio tank. With the patient in an induced coma the damaged tissues are rebuilt at a cellular level under the control of nanotechnology.

In the specialised amnio tanks aboard Venture Star, nutrients and growth stimulants are supplied to the growing avatars, which are taken from childhood to young adulthood during the starship’s five-year flight. For human applications the fluid contains the salt balance of Earth’s oceans; for avatars a more alkaline solution like Pandora’s seas is used.

The growing avatars we see in their amnio tanks are unconscious, but evidently alive. Later in the movie, whenever we see Jake come out of the link, his avatar body falls, unconscious again, yet it clearly stays alive until the next link. So even without the psionic link to its operator the avatar body maintains autonomic functions; its heart beats, its lungs take in air, its blood flows (or at least the avatar’s equivalent of these structures and functions work).

This makes sense. Your mind has some conscious control over your body, at varying levels. You can will your hand to raise, and it rises; you can will yourself to run, and you run. But there is a whole set of neural subfunctions which translate your conscious command into the detailed operations required to fulfil that command. When running you don’t have to think about which leg to lift up next, let alone individually control the various muscle groups to achieve the lifting of that leg. All this interfacing is “downloaded” into the avatar. Driver Jake has to learn to use this interface as he trains with Neytiri; he says he has to “trust my body to know what to do.”

In addition your body has a suite of infrastructure-type functions that operate beyond your conscious control entirely, and many beyond your awareness: they keep your heart beating, your blood circulating, your food being digested. There are even operations going on at the level of the individual cell; bone marrow cells keep producing new blood cells at a rate of millions a minute, every minute. None of this stops working when you forget to think about it, happily. Again all this (or its equivalent) is evidently downloaded into the avatar body.

So the avatar body in the amnio tank is a living creature, with a set of necessary functions in place and operating, long before its first link. And it undergoes some basic “training” of its own during the star flight in support of these functions. In the scene when the new avatars, just off the Valkyrie, are inspected, avatar rider Norm Spellman notes that the bodies have undergone “proprioceptive sims” (that is, simulations) during the journey. As I noted in Chapter 25 proprioception, a sense of position, movement, locomotion, is surely especially important to a tree-climbing quasi-Na’vi like the avatar. And the sims, training these senses into the avatars in their tanks, have the added benefit of improving muscle tone, as Max Patel notes. The in-tank training is based on early, Earth-based experiences. Norm would have worked with his avatar when it was at the developmental stage of a child, playing games to develop motor control. (What fun that must have been!) The games are recorded and replayed to the growing avatar in its amnio tank as developmental exercises.

Perhaps the most revealing bit of dialogue in these scenes is when the techs remark that Jake’s avatar shows no “truncal ataxia.” Ataxia telangiectasia, or Louis-Bar Syndrome, is a rare inherited neurodegenerative disease that affects motor control and weakens the immune system. The first signs of the illness are often detected when the patient is a toddler. “Truncal ataxia” means difficulty with body posture and movement; the child may have difficulty learning to walk. The reference to ataxia reminds us that to the techs the force-grown avatars are indeed children, only a few years old, and they worry about their development like any anxious parent. (All this is impressive scriptwriting, by the way. The creators took care to make the science detail convincing, and to reflect it in the dialogue.)

But the avatars only exist at all because of some pretty advanced genetic engineering. In fact, as hybrids grown from a mix of human and Na’vi genetic material, the avatars may be the twenty-second century’s ultimate GMOs: genetically modified organisms.

In our century a GMO (also known as a GEO, genetically engineered organism) is an organism whose genetic material has been purposefully altered through what is known as “recombinant DNA technology,” in which DNA molecules from different sources are used to create a new set of genes. This material is then implanted into the organism to give it new or modified genes. A “transgenic” GMO takes genes from different species, while a “cisgenic” GMO takes genes only from the organism’s own species. The genes are transferred using viruses, or mechanical means like syringes—techniques used in the genetic therapy I mentioned in Chapter 19.

The first experimental GMO, produced in 1973, was an E. coli bacterium implanted with a salmonella gene. Today GMOs have wide applications, including medical research and the production of drugs. And GMO technology has become a multi-billion-dollar global industry through the use of GMOs in agriculture. Crop strains can be produced that, for example, naturally produce pesticidal proteins. By 2005 over eight million farmers throughout the world were using GMO crops. The controversy over the use of GMOs in agriculture derives partly from uncertainty about their long-term impact on humans, the food chain and indeed the biosphere as a whole, and also from their commercial nature; poorer populations may not derive the benefits of the new crops if they can’t afford the licence to use them. Certainly it is odd to think that we now share our world with life forms that are patent-protected for the benefit of companies like Monsanto of the U.S.

Transgenic animals have also been produced. In 2009 the U.S. Food and Drug Administration gave its first approval to a human-intended drug produced from such an animal: a goat, from whose milk the drug can be extracted. Other animals have been produced for the purpose of biomedical research, and to produce human hormones such as insulin. In 2009 a Japanese firm announced the first transgenic primate, a marmoset. Among the most spectacular applications of all is the Enviropig (the name is trademarked) produced by scientists at a university in Ontario, Canada in 1999, which is said to produce less phosphorus in its manure than unmodified animals.

From Enviropig to avatar! But they are both transgenic animals produced for a specific purpose.

And there’s more to an avatar than simple gene-swapping.

If it were an entirely terrestrial creation, say a mix of human with lemur traits, an avatar would still be an impressive enough application of genetic engineering—far beyond our capabilities today, but whose principles we can clearly grasp. But an avatar is more than this. Jake tells us that avatars are grown using a “mixture of human and native DNA.” A driver’s avatar is derived from his own DNA (or in Jake’s case, his identical twin brother’s). This is necessary to facilitate the synchronising of nervous systems between avatar and driver that makes the psionic link possible.

But the Na’vi are alien creatures, from another star system entirely! How can their “DNA” be “mixed” with ours? Why should they even have “DNA?”

Actually when Jake refers to “native DNA” he’s using the term more generally, to refer to “genetic material” rather than the specific molecule. (To be fair Jake is a Marine; his brother was the science guy…) The purpose of our DNA is to carry genetic information from one generation to the next, and then to use that information in the building of a new life form. “DNA” itself is a term for the specific molecule, deoxyribonucleic acid, that carries out that function for life on Earth. The Na’vi have a similar system but far from identical, based on a different biomolecular set and with a different logic to the coding. Their equivalent of DNA is called NVTranscriptase. (This is an example of how, while the Na’vi are similar to humans externally, they are quite different internally—as proven by the dissection of “specimens.”)

The “mixing” of human and Na’vi genetic material to create a hybrid avatar is done at a logical level. Information from both coding systems is extracted into a computer store, mixed using a translation table, and then downloaded into a third biochemical substrate, the genetics of the avatar.

The resulting hybrids are more Na’vi-like than human, though they have inherited some human features, such as smaller eyes, five-fingered hands. It remains to be seen whether the genetics will allow avatar-Jake and true-Na’vi Neytiri to have children…

However it’s done, growing an avatar in a tank is one thing. Now we must consider an even harder step: linking Jake Sully’s consciousness to it.

³² HACKING THE BRAIN

As a concrete example of the challenges involved in establishing a mental link between Jake and his avatar, let’s consider the scene in which avatar-Jake captures his great leonopteryx by falling down from the sky onto its back. As this is happening human-Jake is motionless in his tank. And yet Jake senses everything the avatar senses, and commands every aspect of its conscious movements. He feels the impact as the avatar lands on the creature’s back, feels the surge of acceleration as the indignant leonopteryx flies off.

How could you make this work?

To some extent Jake is like a player of a virtual reality (VR) system, with the “game” being Pandora as a whole. A virtual reality system feeds what is not real into our senses, well enough to enable us to believe that it is real—or at least well enough to suspend our disbelief.

And in some aspects existing systems do this pretty effectively. A music system is a VR system for the ears, fooling you into imagining there’s a rock band or a symphony orchestra in the room with you. The best modern high-fidelity systems have reached such a level of detailed simulation that the ear can’t tell the difference from the reality. For sight, too, watching the movie Avatar itself in 3-D gives you a flavour of what’s possible in delivering a convincing simulation.

So suppose you constructed an “avatar” like a high-tech robot, laden with cameras, microphones and other sensors. Jake meanwhile is in a wraparound suit with earphones, goggles and maybe with sense-stimulating plugs in his nose and mouth. He is in a motion-capture system of the type Quaritch uses to control his AMP suit, with the machine’s motions aping his own body’s gestures—or like the modern Wii game system. As the leonopteryx looms below the falling robot, you could imagine an all but perfect sensory simulation of the experience being relayed to Jake by all the little cameras and microphones and other sensors: he smells the leonopteryx’s leathery stink, an aroma simulated in some miniature chemical factory, and feels the rushing air of Pandora in his face, blown by tiny fans.

But this is a simulation which would end in dismal disappointment as soon as the robot hit the back of the animal with a shuddering crash—and Jake felt nothing of the impact.

Oh, you could provide human-Jake in his tank with some token jolt, like the little bumps you get in a fairground-ride flight simulator. But here we’ve reached the limit of modern VR technology. We don’t know any way to build systems external to the body to simulate the inner sense of the sharp deceleration that ends a fall, or indeed the acceleration that comes with a rocket launch, say. That’s why astronauts train for zero gravity by floating around in tanks of water, or in planes which make powered falls to provide the illusion of zero gravity for a few seconds: “Vomit Comets.”

You can list plenty of other “inner” sensations Jake needs to experience fully the avatar’s reality. He could be made to feel the Pandoran fruit in his hand, he could taste the juice in the avatar’s mouth—but how could he be made to feel hungry, when the avatar is hungry?

External VR systems of the kind we have today won’t be sufficient. Just as we see in the movie, it is necessary to hack into Jake’s brain to make this work.

In the link room we see Jake, preparing to drive his avatar, lie down in a “psionic link unit.” This has an architecture that looks similar to a modern medical scanner, like a magnetic resonance imager. With this, Max Patel and Grace Augustine are able to extract a three-dimensional image of Jake’s brain, complete with ongoing neural activity.

Then a data link is established between Jake’s brain and the avatar’s, as evidenced by similar-looking images in the scans. The techs speak of achieving “congruency,” as the brains are mapped one to the other. In mathematics, congruent triangles are the same shape and size; you could cut them out and overlay them exactly, though you might have to turn one over to do it. The word is also used in psychology to mean internal and external consistency of the mind. Ultimately “phase lock” is established between the two nervous systems.

What is happening is that the technology is hacking into the input-output systems of Jake’s brain. When he’s outside the link unit, Jake’s brain is connected to his body by a set of neural connections. Sensory information comes flowing into the brain through these connections, and Jake’s commands for his body—lift that arm, jump from that banshee—flow out of his brain. What the link technology has to do is hack into this flow of data, and into the similar flow of data in and out of the avatar’s brain. Sensory input coming in from Jake’s own body must be ignored, and replaced with the data flowing from the avatar’s body. Similarly Jake’s motor-control commands must be diverted from his own body, and transmitted to the avatar body. And all this is done “non-invasively,” in the jargon; the scanning machine manages all this without the need to stick wires into Jake’s skull.

This resolves the problem of inner sensation. It’s as if Jake’s brain has been physically implanted in the avatar’s body. Signals arising from the avatar’s inner proprioceptive senses of falling and then slamming to a halt aboard the leonopteryx are now sent direct to Jake’s brain, so that he “feels” the impact in a way he never could using an external suit.

So that’s the principle. What about the practice? Is this feasible?

Something like the avatar-link process has been studied in the context of “neuroinformatics.” “Mind uploading” is the process of scanning and mapping a biological brain in detail and transferring that data to a computer, or another machine. Clearly this is like half of an avatar link, with a link to a computer store rather than directly to another brain. And it is like the fate of Grace Augustine, when as her human body dies she passes through the “Eye of Eywa,” to become one with the Great Mother—that is, her consciousness is stored in Pandora’s great biological computer. (In this case Eywa was meant to be used as a temporary buffer; Grace’s mind was supposed to return through the Eye of Eywa and then enter her avatar body.)

We have taken some baby steps towards this kind of technology today. In “neuroprosthetics” the nervous system is connected directly to some device. And through a “brain–computer interface” (BCI—a variant is BMI, for brain–machine interface) the brain itself is connected to a computer. Researches in the field began in earnest in the 1970s at the University of California, where the term BCI was first coined.

The first neuroprosthetic applications have been medical, with the aim being the repair of damaged human sensory or motor functions. There have been some attempts to use this technology as an alternative way to treat spinal injuries, like Jake Sully’s. A non-profit consortium called the Walk Again Project has a five-year goal to help a quadriplegic paralysed by a spinal injury to walk again; the patient would use neuroprosthetic devices to control an exoskeleton, an interface reading control signals from the brain to pass to the hardware. The current leading BCI technology is called BrainGate, in which an array of microelectrodes is implanted in the primary motor centre of the brain. In 2008 researchers at the Pittsburgh Medical Center were able to show a monkey operating a robotic arm, with the relevant data being read from the animal’s brain with an invasive implant.

As for writing information to the brain, the most common neuroprosthetic device to date is the cochlear implant, in which deafness is alleviated by a device attached to the skull which directly stimulates the part of the cortex that controls hearing: “writing” a signal derived from auditory data to the appropriate part of the brain. There are also neuroprosthetic devices to restore vision, including retinal implants.

To be able to achieve such feats, you have to be able to understand the brain’s coding of the data it uses: how the firing of a particular set of neurons in a particular way is related to a particular movement of the arm, say. But experiments are proceeding worldwide on reading and understanding motor-control signals, and much more subtle signals, involving mental states associated with language, for example. These are still-tentative steps to something like true mind-reading.

The U.S. military is interested in this kind of technology; the defence research agency DARPA announced a research programme in March 2010. There are ethical concerns however about using such technologies to go beyond meeting clinical needs to enhancing human abilities beyond the natural limits.

Most of these experiments involve invasive procedures, in which the patient’s head is literally invaded by bits of wire. Jake’s scanning is non-invasive—no wires. Is this possible? We do have non-invasive neuroimaging technologies. Techniques include electroencephalography (EEG), the reading of brain waves (which dates back to the 1920s), and magneto-encephalography (MEG) and functional magnetic resonance imaging (fMRI), which are capable of producing three-dimensional images of the brain’s electrical activity. The latter techniques exploit the fact that charged particles, such as those passing between neurons in a brain, give off radiation when moving in a strong magnetic field: signals that can be picked up and analysed. Resolution is a problem; the skull itself dampens signals and blurs the neurons’ signals. Progress is being made. A company called G.Tec, based in Austria, already has a non-invasive system that allows users to control avatars in Second Life. Non-invasiveness only adds to the technical hurdles involved in hacking into the brain.

But even if Jake’s brain is read and written to non-invasively by scanners in the link unit, how is the avatar’s brain accessed? This is the other end of the link, after all, and data must be uploaded and downloaded to it at the same rate as to and from Jake’s brain. In this case the interfacing technology is contained inside the avatar’s brain. As the avatar body is being grown in its tank, the brain is grown with a reception node embedded in its cortex. We haven’t got this far in reality, but there have been experiments with “partially invasive BCIs,” where you lay a thin plastic pad full of sensors within the skull, but outside the brain.

Brain hacking is clearly a tremendous challenge, on which we’ve made barely a start. In the movie, the use of the word “psionic” in the description of the link technology is telling. “Psionics” is generally taken to mean the study of paranormal powers of the mind, such as telepathy, telekinesis, precognition and so forth. It seems to have been coined by science fiction editor John W. Campbell as a fusion of “psi” from psyche, and “onics” from words like electronics, to imply a more scientific framing of the subject. Perhaps we can infer from the use of that word that the science of the twenty-second century has advanced far beyond what is known now; perhaps there are principles at work in the link units of which we have no knowledge.

We can however assume that the link process will be mediated by a computer system vastly more powerful than either Jake’s brain or the avatar’s. The enormous artificial intelligences of the future, as predicted by Moore’s Law, will not be baffled by the computational size of the brain, nor, I would guess, by the challenge of decoding the brain’s many signals. It will be like managing the problem of interfacing an Apple Mac to a Microsoft PC by connecting them both up to that monster Chinese “Milky Way” supercomputer.

And if brain hacking does become possible many remarkable applications open up, beyond the driving of avatars. Fully immersive virtual reality, where we started this discussion, would become trivially easy. Roaming around inside the tremendous computer memories of the future, you could have any experience you want, real or fantastic, as richly detailed as the real world, and you could run them at any speed (compared to real life) as you liked: a twelve-year trip to Pandora and back crammed into a morning coffee-break. If you suffer from “Avatar withdrawal” after watching a mere movie, you might never want to come out of a simulation like that at all.

And VR might become so good that you couldn’t tell what is real and what is virtual, like the characters in the movie The Matrix. I’ve suggested myself that one resolution of the Fermi Paradox (see Chapter 26) is that we’re stuck inside a virtual reality suite run by the aliens, to hide the real universe. Oxford-based philosopher Nick Bostrom says that not only is it possible that we’re living in a virtual reality generated by some advanced culture, it is probable that we are—there are always going to be more copies than the original reality, so it’s more likely you’ll find yourself inside a copy than the original…

We’ve come a long way with this speculation, but we haven’t yet got to the bottom of the mystery of Jake’s mind-linking. For he is interfacing with a body quite unlike his own. And that presents yet more fascinating challenges.

³³ WHAT IS IT LIKE TO BE A NA’VI?

There are lots of subtleties in the way Jake Sully’s mind would have to be mapped into the avatar’s brain, beyond the issues of coding, data transfer rates and all the other information-technology stuff we touched on in the last chapter.

An avatar body is more like a Na’vi’s than a human’s. So to run his avatar, Jake, a human being, has to learn how to be a Na’vi.

I find it a lot easier to imagine that I could drive a fully human avatar than that I could drive an avatar of a Na’vi. Or indeed, an avatar of my own little dog.

For one thing, I’m well aware that my dog doesn’t see the world as I do. This is evident when we watch TV, at least on an old analogue set. Such sets present a series of still images quickly enough to fool the human eye into thinking it’s seeing continuous motion. But my dog’s eyes were evolved for a subtly different purpose than mine, and their “flicker-fusion rate” is faster than mine. He can see the individual frames, and indeed the blanks between them, and so to him the TV screen is like a dance floor under a strobe light. That’s why an analogue TV never captures his interest (but digital sets remove the flicker-fusion problem, and the dog is fascinated, at least by programmes featuring other dogs).

If this is a challenge for my little dog and me, who as mammals are pretty close relatives in the grander scheme of Earth’s family of life, it’s going to be ten times more difficult for Jake and his avatar. After all, Jake and the Na’vi are from different worlds altogether.

The sensory functions of Jake and his avatar overlap, but not completely. For example a Na’vi’s sight goes beyond the human range, into the near infrared, to allow night vision. This provides input which has no analogue in the human sensorium. You could imagine transforming the input images somehow so that they map over the human range; it might be like wearing a soldier’s infrared vision enhancer in a combat zone, and having its images superimposed over the visuals in a heads-up display. But enhancements like that would provide an entirely artificial picture, and would be nothing like what the Na’vi actually sees. Jake has to learn to see like a Na’vi, not like a human with enhancing goggles.

What about hearing? Perhaps those mobile Na’vi ears give their hearing a three-dimensional quality like nothing in the human sensorium. There would be no mechanism in Jake’s head to process such information—no analogy in Jake’s sensory world to map onto.

With motor functions it’s a similar picture. It’s easy to imagine Jake’s brain running a fully human avatar. The region of Jake’s brain that “runs” his right hand can be made, through the link, to “run” the avatar’s right hand; there could be a one-to-one mapping between the driver’s brain and the avatar’s body functions.

But there are areas where a Na’vi’s body function doesn’t map perfectly onto a human brain. The most obvious is that prehensile tail. Jake has no subroutines in his head to work a tail (or if he does they are vestigial, relics of very ancient days when human forebears did have tails). More than that, he doesn’t know how it feels to work a tail. Another entirely nonhuman aspect of the Na’vi experience is the neural link to other animals through the queue. No human has ever experienced such a link; we have no neural subroutines in our brains to process the data coming into the avatar’s head from the direhorse or the banshee.

In 1974 an American philosopher called Thomas Nagel published a paper that has become a classic in its field, called “What Is It Like to Be a Bat?” Exploring issues of consciousness and the “mind-body problem”—how mind arises from the machinery of the body—Nagel was attacking what he called a “wave of reductionist euphoria.” Reductionism is the breaking-down of concepts into smaller pieces for the purpose of measurement and understanding. Nagel argued that consciousness must be tied to “the subjective character of experience,” and so, perhaps, can’t be broken down into little bits.

Nagel’s use of a bat as an example is instructive. A bat is a mammal, like me and my little dog, so pretty closely related to us both, but a bat experiences the world entirely differently from us, primarily through its sonar echolocation system. Its brain processes sound inputs into location and distance information. Inside its head, a bat must “see” the world as a kind of shadowy three-dimensional theatre, painted in auditory data.

Nagel argued that it’s impossible for us to imagine how it must be to be a bat. Even imagining a transition from one form to another—to lose your sight, to have leathery wings strapped to your body, to be hooked up to a sonar system—is an artificial exercise. And (though Nagel didn’t take his argument in this direction) the “reductionist” idea that you could brain-scan a bat and download it into a computer store, without it losing its sense of self as a bat, begins to look a bit silly. Maybe we aren’t just abstract information flows. Maybe everything about our cognition is shaped by the way that we’re embedded in our bodies, because that’s the way we apprehend the universe.

To restate Nagel’s question: what is it like to be a Na’vi? The mapping of Jake’s brain to a Na’vi’s body must require a lot of interfacing, beyond the basic spark-by-spark level of neural inputs and outputs, even beyond the higher-level mapping of Na’vi experience to a human mind. Somehow, the governing software must render the sensations of being a Na’vi into forms capable of being comprehended by Jake, at both sensual and inner levels.

However it works, evidently the psionic link does function in giving the driver a fully immersive experience, as we see from the scenes of Jake’s very first linking—his delight in his new body, and in the world he apprehends. And as the movie goes on we see Jake being drawn steadily into the new world at the expense of the old, almost like an addiction to a computer game, until, as he says, the dream of Pandora seems more real than his own humanity.

And ultimately, following the logic of his personal quest, Jake makes the final step: to leave his humanity behind altogether.

³⁴ THE TRANSMIGRATION OF JAKE SULLY

In the final scenes of the movie Avatar, Jake Sully’s human body lies side by side with his avatar in the Tree of Souls.

This is the conclusion of the long journey Jake began when he left Earth on Venture Star. Like Grace Augustine before him, Jake is attempting to complete a full crossing from his broken human body into the avatar. He must pass through the “Eye of Eywa” to do this. The process failed for Grace, though she was preserved in the “buffer” of Eywa’s neural-net memory.

But, when his avatar’s eyes snap open, we see that Jake succeeds.

Once again these scenes in Avatar are reflections of very old myths, of the transference of souls from the body. The ancient Greeks believed in the transmigration of the soul: after death your shade drinks from the River Lethe, loses all memories of past lives, and moves into another human form and is reborn. Hinduism similarly contains a belief in transmigration.

Today we are still grappling with the implications of such ideas. Jake submits to Eywa, hoping she will choose to “save all that [he] is” in the avatar body. “All that he is”: a concise way to sum up the deepest mystery of human existence. The key questions are: is the copy of Grace inside Eywa really “Grace?” And is Jake in the avatar body really “Jake?”

Before the final transfer, it is evident from shots of Jake in the link tank as he drives the avatar body that there is something of him left behind in his human carcass. His closed eyes flicker, as if he is in “REM sleep” (rapid eye motion). Maybe avatar-driving is like an exceptionally vivid dream. Indeed, a good bit of what makes up Jake must remain in the human body, rather than be downloaded into the avatar’s head: his memories of Earth, for example. And memories from his avatar experiences are stored back in his own brain, for he remembers the experiences after the link is broken. (Transferring memories presents another technical issue for the link mechanism, incidentally. Your memory of the last sentence you read isn’t stored in one place in your head like a little photograph, but is held as a distributed pattern of neuron sparkings.) For Jake to complete the crossing into the avatar, all these memories must be ported over, along with everything else that is a part of his personality.

But even if the entire contents of Jake’s brain are read and downloaded successfully into the avatar, does “Jake” come with it too? What is “Jake?” That is, what is his consciousness, and how is it related to his brain and body?

We are now venturing into waters so deep they make quantum mechanics look like a Sudoku puzzle. Philosophical musings on the nature of the self date back to Plato. In the seventeenth century, Descartes, with his famous declaration “I think therefore I am,” was an early modern western thinker about what has come to be called the “mind-body problem,” the question of how something as ineffable as the human mind can be connected to the lump of meat that is the human body. But other cultures have considered the problem too. The Buddhists, it seems, believe that consciousness is the primary reality.

The position of many modern neuroscientists, as well as visionary futurologists like Ray Kurzweil, is that “Jake,” his mind, everything important about his essence—“all that he is”—derives from the patterns of activity in his brain. Consciousness is an “emergent” quality, and it arises the way a higher-order property like the temperature of a mass of gas “emerges” from the motion of the collection of individual molecules that make up the gas. And if you copy that brain pattern with perfect fidelity, and then if you download that pattern into another substrate, biological or artificial, then yes, that copy still “is” Jake in any meaningful sense.

But not everybody agrees. Philosopher Daniel Dennett has argued the whole Cartesian question of how the mind arises from the body, as if there is a conscious being riding around inside an unconscious carcass, is the wrong question to ask. The mind-body problem would melt away if we could see the workings of the brain closely enough, Dennett says. Consciousness must arise from a flow of information processing between different centres in the brain, so there is no single central consciousness. Consciousness is more like something you do than a thing you are. And if that’s so, is it meaningful to talk of transferring it from the brain at all?

I think it’s true to say that consciousness is still largely a mystery, about which the philosophers and neuroscientists find it difficult even to agree to definitions of terms. Maybe we’re going to have to learn a lot more about how the brain itself works first before we can produce a compelling theory. But new directions in consciousness studies are being followed, including the opening in April 2010 of the new Sackler Centre for Consciousness Science at the University of Sussex in England, which will bring together such disciplines as psychology, neuroscience, medial sciences, computer science and AI studies.

Perhaps in our analysis of mind uploading we have been too reductionist—too eager to break the notions of self down into little pieces. Maybe reality is more subtle. We have seen evidence that there is more to Eywa than the neural network that the great reductionist Grace Augustine was able to sample. Perhaps there is more to “Jake,” to the self, to “all that he is,” than a mere side-effect of neural networks. Maybe, somehow, Eywa really does welcome something like the souls of Grace and Jake into her care, and into the avatar.

And ultimately what Eywa offers Jake and Grace is immortality. If you can upload yourself to a computer store, just as Grace is uploaded to Eywa, then you need never die. Your logical essence has been detached from your physical body, and “you” need no longer be doomed by your body’s ageing process. As future generations of computer technology emerge, you could simply continue to upload yourself to the latest upgraded hardware. Some futurologists like to speak of the coming “singularity,” when thanks to the advance of technology we will merge with the artificial super-brains of the future, and intelligence will advance exponentially.

Perhaps Avatar’s Eywa is a “green” singularity, a merging that is the ultimate destination for all life.

In following the final step of Jake’s journey, from human to the non-human, Avatar has made us confront the deepest questions of our existence. But we have reached the limit of scientific speculation, and can see no further.