he word "cloning" comes to us from the Greek "clon," or twig, and reflects the age-old practice in horticulture of growing new shoots and roots from the clipped-off branches of a mature plant. These cloned individuals are genetically identical to the parent plant, and during the 20th century the concept was expanded to include genetically identical animals—including humans—produced by similar means. Animal clones also occur in nature when a female animal—sometimes even higher animals, like lizards and turkeys—gives "virgin birth" to a genetically identical daughter (this is called parthenogenesis). But in Michael Bay's new (if somewhat cliched) summer thriller, The Island, human clones are kept like farm animals and harvested of their organs and tissues, to extend the lives of their genetic parents.
Possible? Yes. Good basis for a movie? Sure. Plausible in the real world? I'll let you be the judge.
Depending on how far you want to stretch the term, the idea of human cloning may have been introduced in H.G. Wells' 1896 novel The Island of Dr. Moreau, or Fritz Lang's 1927 movie Metropolis. Aldous Huxley's 1932 novel Brave New World is a safer bet, though, because he describes in detail the splitting of a fertilized human egg into dozens of genetically identical workers, fated to toil for the (non-cloned) upper classes. I think it's interesting that then, as now, clones were perceived mainly as disposable slaves, not as ordinary people entitled to ordinary human rights. Any identical twin—or anyone who's ever been friends with one—knows better!
Anyway, Huxley's work probably inspired German scientist Hans Spemann, who in 1938 proposed a method for cloning adult animals which is pretty much how we actually do it today. It's been a staple of science fiction ever since, although in the real world the idea would languish in backwater laboratories for another four decades.
The boys from Brazil are back
Cloning first came to the attention of the general public in 1976, with the publication of Ira Levin's megabestseller, The Boys from Brazil, in which escaped Nazi war criminals secretly raised a crop of teenage Hitlers in South America. Television quickly hopped on the bandwagon with the 1977 pilot of NBC's Quark, written and conceived by comedian Buck Henry. Ironically, it was just a few months later when British biologist John Gurdon announced the successful real-world cloning of frogs, and public interest reached frenzy levels a year later, in the wake of David Rorvick's alleged nonfiction book In His Image: The Cloning of a Man. Rorvick's story was soon revealed as a hoax, though, and the world's attention turned to other matters for another 20 years, until the cloning of Dolly the Sheep made the genetic duplication of mammals a commercial, agricultural and social reality (see "Does Dolly Have Old Age on the Lamb?").
Cloning is not a Xerox machine, though. There's a misconception, still common even among educated people, that a clone is instantly adult, somehow born or decanted or cast from goo at the exact biological age of its parent. This is nonsense, and I have to give George Lucas credit for acknowledging it in his Star Wars prequels. Force-grown by unspecified technology, his clone troopers reach maturity in less than half the time of a normal human. But they begin their lives as babies, and have to learn and grow like everyone else. Bravo. Interestingly, real-world clones also seem to have issues with accelerated or retarded aging.
Still, the single biggest problem with harvesting clones for their organs is that it requires the murder of a fully functional human being. SF writers have occasionally addressed this by floating the idea of mindless clones, specially grown to have nothing more than a primitive brain stem. This is a moral improvement of sorts, but the shudders of public reaction tell us it's no more likely to be condoned. In fact, worldwide, public opinion has come down pretty hard on the idea of cloning people at all.
But what if we could clone just a single body part? An eye, a pancreas, a cluster of neurons or a shiny new immune system? This is the goal of so-called "therapeutic cloning," which employs the same process as reproductive cloning—replacing the nucleus of an egg cell with one from a patient's mature body cell—but does not produce a viable embryo. Instead, the dividing egg produces embryonic stem cells that carry the patient's own genome and can be injected into specific sites to regrow damaged tissues. This process is not yet an exact science—it sometimes leads to cancer or other badnesses—but it's one of the most promising new therapies in medicine today (see "20 Tot Teeth Later"). Unfortunately, even this raises ethical concerns, since it involves a human egg and creates an "embryo" that could, under the right circumstances, be coaxed to grow into a human being.
Winding the stem of life
Science needn't—and indeed, probably shouldn't—take a "right or wrong" position on these opinions. They simply are what they are, and any research that violates them is going to meet with opposition. But there's a technical solution for nearly every problem this world has to offer, and therapeutic cloning is no exception. All we have to do is find a way to convert adult stem cells (which can grow only into specific tissues) into embryonic stem cells (which can grow into anything). This is a tall order, but labs all over the world are working on it, and I'll be shocked if they don't unlock the secret sometime in the next 20 years. And while the doctors of today collect stem cells with an agonizing bone marrow extraction, the doctors of tomorrow may harvest them painlessly from human tears.
Stem cells are currently used to treat hundreds of illnesses. They're really good, for example, at strengthening a weakened heart muscle, or filling in gaps in a brain with Parkinson's disease. When you need to regrow an entire organ, though, things get a bit more complicated. The science of "tissue engineering" addresses these challenges by injecting stem cells into scaffolds made of collagen and biodegradable polymers, bathing them in nutrients, treating them with assorted hormones and growth factors, and finally moving them surgically into a living body. If this sounds complex, don't worry. It is.
But the animal kingdom has its own, much simpler ways of handling these things. In a word: regeneration. Many invertebrates can regrow almost any lost body part, and within the vertebrate subphylum the newt and salamander are top regenerators. Mammals have only limited regeneration capability, with humans having some of the weakest of all. Interestingly, though, we still retain the genes that are implicated in the process. Current thinking is that our immune systems (which are a lot more complex than a newt's) interfere with the regrowth in some way. This may be an overall survival advantage for the human species, but for humans with serious injuries it's a real drag.
So imagine a future where accident victims are packed off into a sterile cleanroom, where their immune systems are turned off and their injury sites are injected with special hormones, and a week later they emerge, as good as new. This may be less dramatic than a clone-ranch jailbreak, but it's surely a lot easier to arrange. In extreme cases we can even imagine a severed limb being tossed into a nutrient tank and regrown into a whole new person! Starfish do it all the time. Such a branch-grown human—a "clon," if you will—wouldn't retain the memories of its original body, but as with deep amnesia, these could be relearned.
Or not; the arm could choose to live an entirely different life, as a genetically identical but legally distinct human being. I think most people would rather have kids the old-fashioned way, but hey, it's always nice to have options. Gives new meaning to the term "a chip off the old block," doesn't it?
Sources:
Wikipedia: ("cloning," "tissue engineering," "regeneration"): http://en.wikipedia.org
The Encyclopedia Britannica Ultimate Reference DVD, 2004 Edition ("clone")
Nichols, Peter: The Science in Science Fiction, Knopf, 1983
Weiss, Peter: "Putting Squish into Artificial Organs," Science News, 29 June 2002
Foster, Steven C.: "Central Sterile Corneal Ulceration," http://www.emedicine.com/oph/topic746.htm
The Internet Movie Database (http://www.imdb.com)
CNN Cloning Timeline: http://edition.cnn.com/interactive/health/0108/cloning.timeline/content.html
The Encyclopedia Britannica, 2004 Edition ("clone," "regeneration")
Wil McCarthy is a rocket guidance engineer, robot designer, nanotechnologist, science-fiction author and occasional aquanaut. He has contributed to three interplanetary spacecraft, five communication and weather satellites, a line of landmine-clearing robots and some other "really cool stuff" he can't tell us about. His short writings have graced the pages of Analog, Asimov's, Wired, Nature and other major publications, and his book-length works include the New York Times notable Bloom, Amazon "Best of Y2K" The Collapsium and, debuting this month, To Crush the Moon. His acclaimed nonfiction book, Hacking Matter, is now available in paperback.
