FOUNTAIN OF YOUTH?.
One unwanted by-product of this discovery, however, has been the media circus that it sparked. Suddenly, 60 Minutes 60 Minutes and and The Oprah Winfrey Show The Oprah Winfrey Show featured resveratrol, creating a stampede on the Internet, with fly-by-night companies springing up overnight, promising the elixir of life. It seems as if every snake oil salesman and charlatan wanted to jump on the resveratrol bandwagon. featured resveratrol, creating a stampede on the Internet, with fly-by-night companies springing up overnight, promising the elixir of life. It seems as if every snake oil salesman and charlatan wanted to jump on the resveratrol bandwagon.
(I had a chance to interview Guarente, the man who started this media stampede, in his laboratory. He was cautious in his statements, realizing the media impact that his results may have and the misconceptions that may develop. In particular, he was incensed that so many Internet sites are now advertising resveratrol as some sort of fountain of youth. It was appalling, he noted, that people were trying to cash in on the sudden fame that resveratrol has gotten, although most of the results are still tentative. However, he wouldn"t rule out the possibility that one day, if the fountain of youth is ever found, a.s.suming it even exists, then SIR2 may play a part. His colleague Sinclair, in fact, admits that he takes large quant.i.ties of resveratrol every day.) Interest in aging research is so intense within the scientific community that Harvard Medical School sponsored a conference in 2009 that drew some of the major researchers in the field. In the audience were many who were personally undergoing caloric restriction. Looking gaunt and frail, they were putting their scientific philosophy to the test by restricting their diets. There were also members of the 120 Club, who intend to live to the age of 120. In particular, interest was focused on Sirtris Pharmaceuticals, cofounded by David Sinclair and Christoph Westphal, which is now putting some of their resveratrol subst.i.tutes through clinical trials. Westphal says flatly, "In five or six or seven years, there will be drugs that prolong longevity."
Chemicals that did not even exist a few years ago are the subject of intense interest as they go through trials. SRT501 is being tested against multiple myeloma and colon cancer. SRT2104 is being tested against type 2 diabetes. Not only sirtuins but also a host of other genes, proteins, and chemicals (including IGF-1, TOR, and rapamycin) are being closely a.n.a.lyzed by various groups.
Only time will tell if these clinical trials will be successful. The history of medicine is riddled with tales of deception, chicanery, and fraud when it comes to the aging process. But science, not superst.i.tion, is based on reproducible, testable, and falsifiable data. As the National Inst.i.tute on Aging sets up programs to test various substances for their effects on aging, then we will see if these intriguing studies on animals carry over to humans.
DO WE HAVE TO DIE?.
William Haseltine, a biotech pioneer, once told me, "The nature of life is not mortality. It"s immortality. DNA is an immortal molecule. That molecule first appeared perhaps 3.5 billion years ago. That selfsame molecule, through duplication, is around today.... It"s true that we run down, but we"ve talked about projecting way into the future the ability to alter that. First to extend our lives two- or threefold. And perhaps, if we understand the brain well enough, to extend both our body and our brain indefinitely. And I don"t think that will be an unnatural process."
Evolutionary biologists point out that evolutionary pressure is placed on animals during their reproductive years. After an animal is past its reproductive years, it may in fact become a burden on the group and hence perhaps evolution has programmed it to die of old age. So perhaps we are programmed to die. But maybe we can reprogram ourselves to live longer.
Actually, if we look at mammals, for example, we find that the larger the mammal, the lower its metabolism rate, and the longer it lives. Mice, for example, burn up an enormous amount of food for their body weight, and live for only about four years. Elephants have a much slower metabolism rate and live to seventy. If metabolism corresponds to the buildup of errors, then this apparently agrees with the concept that you live longer if your metabolism rate is lower. (This may explain the expression "burning the candle at both ends." I once read a short story about a genie who offered to grant a man any wish he wanted. He promptly asked to live 1,000 years. The genie granted him his wish and turned him into a tree.) Evolutionary biologists try to explain life span in terms of how longevity may help a species survive in the wild. To them, a specific life span is determined genetically because it helps the species to survive and flourish. Mice live so briefly, in their view, because they are constantly being hunted by a variety of predators and often freeze to death in winter. The mice that pa.s.s on their genes to the next generation are the ones that have the most offspring, not the ones who live longer. (If this theory is correct, then we expect that mice that can somehow fly away from predators would live longer. Indeed, bats, which are the same size as mice, live 3.5 times longer.) But one anomaly comes from the reptiles. Apparently, certain reptiles have no known life span. They might even live forever. Alligators and crocodiles simply get larger and larger, but remain as vigorous and energetic as ever. (Textbooks often claim that alligators live to be only seventy years of age. But this is perhaps because the zookeeper died at age seventy. Other textbooks are more honest and simply say that the life span of these creatures is greater than seventy but has never been carefully measured under laboratory conditions.) In reality, these animals are not immortal, because they die of accidents, starvation, disease, etc. But if left in a zoo, they have enormous life spans, almost seeming to live forever.
BIOLOGICAL CLOCK.
Another intriguing clue comes from the telomeres of a cell, which act like a "biological clock." Like the plastic tips at the ends of shoelaces, the telomeres are found at the ends of a chromosome. After every reproduction cycle, they get shorter and shorter. Eventually, after sixty or so reproductions (for skin cells), the telomeres unravel. The cell then enters senescence and ceases to perform properly. So the telomeres are like the fuse on a stick of dynamite. If the fuse gets shorter after each reproduction cycle, eventually the fuse disappears and the cell stops reproducing.
This is called the Hayflick limit, which seems to put an upper limit on the life cycle of certain cells. Cancer cells, for example, have no Hayflick limit and produce an enzyme called telomerase that prevents the telomeres from getting shorter and shorter.
The enzyme telomerase can be synthesized. When applied to skin cells, they apparently reproduce without limit. They become immortal.
However, there is a danger here. Cancer cells are also immortal, dividing without limit inside a tumor. In fact, that is why cancer cells are so lethal, because they reproduce without limit, until the body can no longer function. So the enzyme telomerase has to be a.n.a.lyzed carefully. Any therapy using telomerase to rewind the biological clock must be checked to make sure it does not cause cancer.
IMMORTALITY PLUS YOUTH.
The prospect of extending the human life span is a source of joy for some and a horror for others, as we contemplate a population explosion and a society of decrepit elderly who will bankrupt the country.
A combination of biological, mechanical, and nanotechnological therapies may in fact not only increase our life span but also preserve our youth in the process. Robert A. Freitas Jr., who applies nanotechnology to medicine, has said, "Such interventions may become commonplace a few decades from today. Using annual checkups and cleanouts, and some occasional major repairs, your biological age could be restored once a year to the more or less constant physiological age that you select. You might still eventually die of accidental causes, but you"ll live at least ten times longer than you do now."
In the future, extending the life span will not be a matter of drinking of the fabled Fountain of Youth. More likely, it will be a combination of several methods: 1.growing new organs as they wear out or become diseased, via tissue engineering and stem cells 2.ingesting a c.o.c.ktail of proteins and enzymes that are designed to increase cell repair mechanisms, regulate metabolism, reset the biological clock, and reduce oxidation 3.using gene therapy to alter genes that may slow down the aging process 4.maintaining a healthy lifestyle (exercise and a good diet) 5.using nanosensors to detect diseases like cancer years before they become a problem
POPULATION, FOOD, AND POLLUTION.
But one nagging question is: If life expectancy can be increased, then will we suffer from overpopulation? No one knows.
Delaying the aging process brings up a host of social implications. If we live longer, won"t we overpopulate the earth? But some point out that the bulk of life extension has already happened, with life expectancy exploding from forty-five to seventy to eighty in just one century. Instead of creating a population explosion, it has arguably done the reverse. As people are living longer, they are pursuing careers and delaying childbearing. In fact, the native European population is actually decreasing dramatically. So if people live longer and richer lives, they might s.p.a.ce out their children accordingly, and have fewer of them. With many more decades to live, people will reset their time frames accordingly, and hence s.p.a.ce out or delay their children.
Others claim that people will reject this technology because it is unnatural and may violate their religious beliefs. Indeed, informal polls taken of the general population show that most people think that death is quite natural and helps to give life meaning. (However, most of the people interviewed in these polls are young to middle-aged. If you go to a nursing home, where people are wasting away, living with constant pain, and waiting to die and ask the same question, you might get an entirely different answer.) As UCLA"s Greg Stock says, "Gradually, our agonizing about playing G.o.d and our worries about longer life spans would give way to a new chorus: "When can I get a pill?""
In 2002, with the best demographic data, scientists estimated that 6 percent of all humans who have ever walked the face of the earth are still alive today. This is because the human population hovered at around 1million for most of human history. Foraging for meager supplies of food kept the human population down. Even during the height of the Roman Empire, its population was estimated to be only 55 million.
But within the last 300 years, there has been a dramatic spike in world population coincident with the rise of modern medicine and the Industrial Revolution, which produced a bounty of food and supplies. And in the twentieth century, the world population soared to new heights, more than doubling from 1950 to 1992: from 2.5 billion to 5.5 billion. It now stands at 6.7 billion. Every year, 79 million people join the human race, which is more than the entire population of France.
As a result, many predictions of doomsday have been made, yet so far humanity has been able to dodge the bullet. Back in 1798, Thomas Malthus warned us what would happen when the population exceeded the food supply. Famines, food riots, the collapse of governments, and ma.s.s starvation could ensue until a new equilibrium is found between population and resources. Since the food supply expands only linearly with time, while the population grows exponentially, it seemed inevitable that at some point the world would hit the breaking point. Malthus predicted ma.s.s famines by the mid-1800s.
But in the 1800s, the world population was only in the early stages of major expansion, and because of the discovery of new land, the founding of colonies, increases in the food supply, etc., the disasters Malthus predicted never took place.
In the 1960s, another Malthusian prediction was made, stating that a population bomb would soon hit the earth, with global collapse by the year 2000. The prediction was wrong. The green revolution successfully expanded the food supply. The data show that the increase in food supply exceeded the growth in the world population, thereby temporarily defeating the logic of Malthus. From 1950 to 1984, grain production increased by more than 250 percent, mainly due to new fertilizers and new farming technologies.
Once again, we were able to dodge the bullet. But now the population expansion is in full swing, and some say we are reaching the limit of the earth"s ability to create food supplies.
Ominously, food production is beginning to flatten out, both in world grain production and in food harvested from the oceans. The UK government"s chief scientist warned of a perfect storm of exploding population and falling food and energy supplies by 2030. The world will have to produce 70 percent more food by 2050 to feed an extra 2.3 billion people, the UN"s Food and Agriculture Organization has said, or else face disaster.
These projections may underestimate the true scope of the problem. With hundreds of millions of people from China and India entering the middle cla.s.s, they will want to enjoy the same luxuries that they have seen in Hollywood movies-such as two cars, s.p.a.cious suburban homes, hamburgers and French fries, etc.-and may strain the world"s resources. In fact, Lester Brown, one of the world"s leading environmentalists and founder of the World Watch Inst.i.tute in Washington, D.C., confided to me that the world may not be able to handle the strain of providing a middle-cla.s.s lifestyle to so many hundreds of millions of people.
SOME HOPE FOR WORLD POPULATION.
There are some glimmers of hope, however. Birth control, once a taboo topic, has taken hold in the developed world and is making inroads in the developing world.
In Europe and j.a.pan, we see the implosion, not the explosion, of the population. The birthrate is as low as 1.2 to 1.4 children per family in some European nations, far below the replacement level of 2.1. j.a.pan is being hit with a triple whammy. One, it has the fastest-aging population on earth. j.a.panese women, for example, have held the record for more than twenty years for having the longest life expectancy of any group. Two, j.a.pan has a plunging birthrate. And three, the government keeps immigration extremely low. These three demographic forces are creating a train wreck in slow motion. And Europe is not far behind.
One lesson here is that the world"s greatest contraceptive is prosperity. In the past, peasants without retirement plans or social security tried to have as many children as possible to toil in the fields and care for them when they got old, doing a simple calculation: each new child in the family means more hands to work, more income, and more people to nurse you in old age. But when a peasant enters the middle cla.s.s, complete with retirement benefits and a comfortable lifestyle, the equation flips the other way: each child reduces income and quality of life.
In the third world, you have the opposite problem-a rapidly expanding population, where much of the population is below the age of twenty. Even where the population explosion is expected to be the largest, in Asia and sub-Saharan Africa, the birthrate has been falling, for several reasons.
First, you have the rapid urbanization of the peasant population, as farmers leave their ancestral lands to try their luck in the megacities. In 1800, only 3 percent of the population lived in cities. By the end of the twentieth century, that figure rose to 47 percent, and it is expected to soar above that in the coming decades. The expense of child rearing in the city drastically reduces the number of children in a family. With rents, food, and expenses being so high, workers in the slums of the megacities perform the same calculus and conclude that each child reduces their wealth.
Second, as countries industrialize, as in China and India, this creates a middle cla.s.s that wants fewer children, as in the industrialized West. And third, the education of women, even in poor countries like Bangladesh, has created a cla.s.s of women who want fewer children. Because of an extensive educational plan, the birthrate in Bangladesh has gone down from 7 to 2.7, even without large-scale urbanization or industrialization.
Given all these factors, the UN has continually revised its figures about future population growth. Estimates still vary, but the world population may hit 9 billion by 2040. Although the population will continue to increase, the rate of growth will eventually slow down and level off. Optimistically, it may even stabilize at around 11 billion by 2100.
Normally, one might consider this to be beyond the carrying capacity of the planet. But it depends on how one defines carrying capacity, because there might be another green revolution in the making.
One possible solution to some of these problems is biotechnology. In Europe, bioengineered foods have earned a bad reputation that may last for an entire generation. The biotech industry simultaneously marketed herbicides to farmers as well as herbicide-resistant crops. To the biotech industry, this meant more sales, but to the consumer, this meant more poisons in their food, and the market quickly imploded.
In the future, however, grains such as "super-rice" may enter the market, that is, crops specifically engineered to thrive in dry, hostile, and barren environments. On moral grounds, it would be difficult to oppose the introduction of crops that are safe and can feed hundreds of millions of people.
RESURRECTING EXTINCT LIFE-FORMS.
But other scientists are not just interested in extending human life span and cheating death. They are interested in bringing back creatures from the dead.
In the movie Jura.s.sic Park, Jura.s.sic Park, scientists extract DNA from the dinosaurs, insert it into the eggs of reptiles, and bring dinosaurs back to life. Although usable DNA from dinosaurs has so far never been found, there are tantalizing hints that this dream is not totally far-fetched. By the end of this century, our zoos may be populated by creatures that ceased walking the surface of the earth thousands of years ago. scientists extract DNA from the dinosaurs, insert it into the eggs of reptiles, and bring dinosaurs back to life. Although usable DNA from dinosaurs has so far never been found, there are tantalizing hints that this dream is not totally far-fetched. By the end of this century, our zoos may be populated by creatures that ceased walking the surface of the earth thousands of years ago.
As we mentioned earlier, Robert Lanza took the first major step by cloning banteng, an endangered species. It would be a shame, he feels, if this rare ox dies out. So he is considering another possibility: creating a new cloned animal, but of the opposite s.e.x. In mammals, the s.e.x of an organism is determined by the X and Y chromosomes. By tinkering with these chromosomes, he is confident he can clone another animal from this carca.s.s, except of the opposite s.e.x. In this way, zoos around the world could enjoy watching animals from long-dead species have babies.
I once had dinner with Richard Dawkins of Oxford University and author of The Selfish Gene, The Selfish Gene, who takes this a step further. He speculates that one day we might be able to resurrect a variety of life-forms that are not just endangered but also have been long extinct. He first notes that every twenty-seven months, the number of genes that have been sequenced doubles. Then he calculates that in the coming decades it will cost only $160 to fully sequence anyone"s genome. He envisions a time when biologists will carry a small kit with them and then, within minutes, be able to sequence the entire genome of any life-form they encounter. who takes this a step further. He speculates that one day we might be able to resurrect a variety of life-forms that are not just endangered but also have been long extinct. He first notes that every twenty-seven months, the number of genes that have been sequenced doubles. Then he calculates that in the coming decades it will cost only $160 to fully sequence anyone"s genome. He envisions a time when biologists will carry a small kit with them and then, within minutes, be able to sequence the entire genome of any life-form they encounter.
But he goes further and theorizes that, by 2050, we will be able to construct the entire organism from its genome alone. He writes, "I believe that by 2050, we shall be able to read the language [of life]. We shall feed the genome of an unknown animal into a computer which will reconstruct not only the form of the animal but the detailed world in which its ancestors...lived, including their predators or prey, parasites or hosts, nesting sites, and even hopes and fears." Quoting from the work of Sydney Brenner, Dawkins believes that we can reconstruct the genome of the "missing link" between humans and the apes.
This would be a truly remarkable breakthrough. Judging from the fossil and DNA evidence, we separated from the apes about 6 million years ago.
Since our DNA differs from that of chimpanzees by only 1.5 percent, in the future a computer program should be able to a.n.a.lyze our DNA and the chimpanzee"s DNA and then mathematically approximate the DNA of the common ancestor who gave birth to both species. Once the hypothetical genome of our common ancestor is mathematically reconstructed, a computer program will then give us a visual reconstruction of what it looked like, as well as its characteristics. He calls this the Lucy Genome Project, named after the celebrated fossil of an Australopithecus. Australopithecus.
He even theorizes that once the genome of the missing link has been mathematically re-created by a computer program, it might be possible to actually create the DNA of this organism, implant it into a human egg, and then insert the egg into a woman, who will then give birth to our ancestor.
Although this scenario would have been dismissed as preposterous just a few years ago, several developments indicate that it is not such a far-fetched dream.
First, the handful of key genes that separate us from the chimpanzees are now being a.n.a.lyzed in detail. One interesting candidate is the ASPM gene, which is responsible for controlling brain size. The human brain increased in size several million years ago, for reasons that are not understood. When this gene is mutated, it causes microcephaly, in which the skull is small and the brain reduced by 70 percent, about the size of our ancient ancestors" millions of years ago. Intriguingly, it is possible using computers to a.n.a.lyze the history of this gene. a.n.a.lyses show that it mutated fifteen times in the last 5 to 6 million years, since we separated from the chimpanzees, which coincides with the increase in our brain size. Compared to our primate cousins, humans have experienced the fastest rate of change in this key gene.
Even more interesting is the HAR1 region of the genome, which contains only 118 letters. In 2004, it was discovered that the crucial difference between chimps and humans in this region was just 18 letters, or nucleic acids. Chimps and chickens diverged 300 million years ago, yet their base pairs in the HAR1 region differ by only two letters. What this means is that the HAR1 region was remarkably stable throughout evolutionary history, until the coming of humans. So perhaps the genes that make us human are contained there.
But there is an even more spectacular development that makes Dawkins"s proposal seem feasible. The entire genome of our nearest genetic neighbor, the long-extinct Neanderthal, has now been sequenced. Perhaps by computer a.n.a.lysis of the genome of humans, chimpanzees, and Neanderthals, one might use pure mathematics to reconstruct the genome of the missing link.
BRING BACK THE NEANDERTHAL?.
Humans and the Neanderthals probably diverged about 300,000 years ago. But these creatures died out about 30,000 years ago in Europe. So it was long thought that it was impossible to extract usable DNA from long-dead Neanderthals.
But in 2009, it was announced that a team led by Svante Paabo of the Max Planck Inst.i.tute for Evolutionary Anthropology in Leipzig had produced a first draft of the entire Neanderthal genome, a.n.a.lyzing the DNA from six Neanderthals. This was a monumental achievement. The Neanderthal genome, as expected, was very similar to the human genome, both containing 3 billion base pairs, but also different in key respects.
Anthropologist Richard Klein of Stanford, commenting on this work of Paabo and his colleagues, said that this reconstruction might answer long-standing questions about Neanderthal behavior, such as whether they could talk. Humans have two particular changes in the FOXP2 gene, which, in part, allow us to speak thousands of words. A close a.n.a.lysis shows that the Neanderthal had the same two genetic changes in its FOXP2 gene. So it is conceivable that the Neanderthal might have been able to vocalize in a way similar to us.
Since the Neanderthals were our closest genetic relative, they are a subject of intense interest among scientists. Some have raised the possibility of one day reconstructing the DNA of the Neanderthal and inserting it into an egg, which may one day become a living Neanderthal. Then, after thousands of years, the Neanderthal may one day walk the surface of the earth.
George Church of the Harvard Medical School even estimated that it would cost only $30 million to bring the Neanderthal back to life, and he even laid out a plan to do so. One could first divide the entire human genome into chunks, with 100,000 DNA pairs in each piece. Each one would be inserted into a bacterium and then altered genetically so the genome matched that of the Neanderthal. Each of these altered chunks of DNA would then be rea.s.sembled into the complete Neanderthal DNA. This cell would then be reprogrammed to revert to its embryonic state and then inserted into the womb of a female chimp.
However, Klein of Stanford brought up some reasonable concerns when he asked, "Are you going to put them in Harvard or in a zoo?"
All this talk of resurrecting another long-extinct species like the Neanderthal "will doubtless raise ethical worries," cautions Dawkins. Will the Neanderthal have rights? What happens if he or she wants to mate? Who is responsible if he or she gets hurt or hurts someone else?
So if the Neanderthal can be brought back to life, can scientists eventually create a zoo for long-extinct animals, like the mammoth?
BRING BACK THE MAMMOTH?.
The idea is not as crazy as it sounds. Already, scientists have been able to sequence much of the genome of the extinct Siberian mammoth. Previously, only tiny fragments of DNA had been extracted from woolly mammoths that were frozen in Siberia tens of thousands of years ago. Webb Miller and Stephan C. Schuster of Pennsylvania State University did the impossible: they extracted 3 billion base pairs of DNA from the frozen carca.s.ses of the mammoths. Previously, the record for sequencing the DNA of an extinct species was only 13 million base pairs, less than 1 percent of the animal"s genome. (This breakthrough was made possible by a new sequencing machine, called the high-throughput sequencing device, that allows one to scan thousands of genes at once, rather than individually.) Another trick was knowing where to look for ancient DNA. Miller and Schuster found that the hair follicle of the woolly mammoth, not the body itself, contained the best DNA.
The idea of resurrecting an extinct animal may now be biologically possible. "A year ago, I would have said this was science fiction," Schuster said. But now, with so much of the mammoth genome sequenced, this is no longer out of the question. He even sketched how this might be done. He estimated that perhaps only 400,000 changes in the DNA of an Asian elephant could create an animal that had all the essential features of a woolly mammoth. It might be possible to genetically alter the elephant"s DNA to accommodate these changes, insert this into the nucleus of an elephant egg, and then implant the egg into a female elephant.
Already, the team is looking to sequence the DNA from yet another extinct animal, the thylacine, an Australian marsupial, closely related to the Tasmanian devil, that became extinct in 1936. There is also some talk of sequencing the dodo bird. "Dead as a dodo" is a common expression, but it may become obsolete if scientists can extract usable DNA from the soft tissue and bones of carca.s.ses of dodos that exist in Oxford and elsewhere.
JURa.s.sIC PARK?.
This naturally leads to the original question: Can we resurrect the dinosaurs? In a word, perhaps no. A Jura.s.sic Park depends on being able to retrieve the intact DNA of a life-form that died out more than 65 million years ago, and this may be impossible. Although soft tissue has been found within the thigh bones of dinosaur fossils, so far no DNA has been extracted in this way, only proteins. Although these proteins have chemically proven the close relationship between the Tyrannosaurus rex Tyrannosaurus rex and the frog and chicken, this is a far cry from being able to reclaim the genome of a dinosaur. and the frog and chicken, this is a far cry from being able to reclaim the genome of a dinosaur.
Dawkins holds out the possibility, however, of being able to genetically compare the genome of various bird species with reptiles and then mathematically reconstruct the DNA sequence of a "generalized dinosaur." He notes that it is possible to induce chicken beaks to grow tooth buds (and induce snakes to grow legs). Hence, ancient characteristics, which have long vanished into the sands of time, might be lingering within genomes.
This is because biologists now realize that genes can be turned on and hence can also be turned off. This means that the genes for ancient characteristics may still exist but simply be dormant. By turning on these long-dormant genes, it might be possible to bring back these ancient traits.
For example, in the ancient past, chicken feet once had webbing. The gene for webbing did not disappear but was simply turned off. By turning this gene back on, one can in principle create chicken with webbed feet. Similarly, humans once were covered with fur. However, we lost our fur when we began to sweat, which is a very efficient way to regulate the temperature of the body. (Dogs don"t have sweat glands, and so cool themselves off by panting.) The gene for human fur apparently still exists but has been turned off. Thus, by turning on this gene, it might be possible to have people with fur all over their bodies. (Some have speculated that this may be responsible for the werewolf legend.) If we a.s.sume that some of the genes of the dinosaurs were in fact turned off for millions of years but still survive in the genome of birds, then it might be possible to reactivate these long-dormant genes and induce dinosaur characteristics in birds. So Dawkins"s proposal is speculative but not out of the question.
CREATING NEW LIFE-FORMS.
This raises the final question: Can we create life according to our wishes? Is it possible to create not just long-extinct animals but also animals that have never existed before? For example, could we make a pig with wings or an animal described in ancient mythology? Even by the end of this century, science will not be able to create animals to order. However, science will go a long way to being able to modify the animal kingdom.
So far, the limiting factor has been our ability to move genes around. Only single genes can be reliably modified. For example, it is possible to find a gene that causes certain animals to glow in the dark. This gene can be isolated, then placed in other animals so they glow in the dark. In fact, research is currently going on whereby family pets may be modified by the addition of single genes.
But creating an entirely new animal, like a chimera from Greek mythology (which is the combination of three different animals), requires the transposition of thousands of genes. To create a pig with wings, you would have to move the hundreds of genes that represent the wing and make sure all the muscles and blood vessels match up properly. This is far beyond anything that can be done today.