Can scientists clone dinosaurs?
Since the Steven Spielberg classic, "Jurassic Park," put the question of cloning dinosaurs in the public conscience, the idea evolved into a mountain to climb as genetics made leapfrog advances in research. But science has since indicated the mountain was a little different than thought when Spielberg was spinning the reels of his prehistoric imagination factory: the feathers of today's descendants might not have been completely absent on the raptors, or T-Rex, and that T-Rex was not the largest of the thunderous lizards, and that, rather than a stalking, springing, spitting, jeep-chasing, slashing predator, it was far more likely to have been a more lethargic, lumbering, hither-come-lately scavenger, cleaning up the scraps of others. No matter. Let's make one, put it in a zoo, somewhere, and feed it goats, cows, and the occasional unthinking patron or careless keeper who somehow crosses whatever boundaries are placed between it and us: "T-Rex devours visitor in freak zoo mishap."
Can science make that headline come true by cloning a hulking, down-feathered, large-toothed garbage can? The answer is, "Yes." Essentially the same technology that, in 1952, cloned the first animal, a frog, and which became more and more refined, using a nuclear-transfer procedure to clone the first mammal, Dolly, the sheep, "could" be used to clone dinosaurs. Since Dolly, reproductive cloning has successfully sent many animals to the near-replicates farm, including most of the leading cartoon celebrities: Bugs, Sylvester, Mickey, Elsie, and Piggly Wiggly, among others. Reproductive cloning, using nuclear transfer, "somatic cell nuclear transfer," or SCNT, to be specific, is the process of transferring mature genetic material (from DNA) from the cell-nucleus of one animal to the egg of another, an egg in which the nucleus has been removed. But even though the egg no longer has a nucleus, a bit of its mitochondria combines with the donor DNA, which makes the new animal somewhat less than an exact replica. SCNT is only one of three types of processes by which cloning can be achieved.
Therapeutic, or embryo cloning is the second type, and it is limited to human-cell production. Therapeutic cloning is the process that has the most interest in medicine, and ethics, since this is the process by which scientists have used stem cells for the specific purpose of generating replacement body parts, from organs to skin, and which is seen as the most promising way to create agents dedicated to a particular individual to combat disease and repair damage. The most recent breakthrough in this type of cloning research (performed on animals, mice, in this case) involves muscle tissue, where genetic engineers have found a way to monitor the development of stem cells as they grow into muscles within the test mammal. This could result in a drug to replace damaged muscles in humans, which would be significant for those afflicted with muscular dystrophy, as well as those whose muscle tissues are damaged through external forces, like gunshots, or athletic-performance damage.
In the motion picture, "Jurassic Park," the dinosaurs were cloned using the third method, Recombinant DNA Technology, or DNA cloning, also called "gene" or "molecular" cloning, and this process, invented in the 1970's, "could" recreate dinosaurs in the real world, as well. DNA cloning is the prevalent technology employed in molecular biology today, and it is similar to SCNT, in that the donor DNA is transferred to create the new animal. But the difference is that, instead of being transferred to an egg, sans-nucleus, where mitochondrial mutations are introduced, a non-corrupting, self-replicating, genetic-growth substance is employed: either a virus, artificial bacterial or yeast chromosomes, or most often, a bacterial plasmid, all of which allow propagation of the recombinant, donor DNA in host cells that are unrelated to the donor.
So, the question is really not whether science can clone a dinosaur, which it could, but rather, "can viable dinosaur DNA ever be found to go through the process?" Crime dramas on TV have provided an awareness of the difficulty of obtaining viable DNA from corpses for the purpose of identification. Identification! Replication is far-more demanding of the DNA and its genetic material, and that material is easily mutated or destroyed by many factors, including heat, ultra-violet, and dehydration. The genetic material must be entirely viable, alive, to be cloned. So as bad as the prospects of rebirth are for DNA in a corpse, a corpse is not a fossil, which is where the living bones and tissue, that which hasn't been scoured by scavengers and bacteria, has been mineralized, turned into stone. You can't find DNA in a stone, so if there is any to be had, it will have to be preserved in some other, more gentle process.
Never say never?
There may be some circumstance, somewhere, where some prehistoric DNA of some kind of higher animal (better hypothetical odds not to limit the search to an actual dinosaur) remains tucked away, viable, and ready to be made into a copy of itself. But even so, finding it would be pure chance, and that chance would have to cash-in on an extremely scarce opportunity. Insects trapped in amber have been found unsuitable for any of the three cloning processes, so far, although there actually has been prehistoric life found that survived the millennia in hibernation: spores of bacteria, found within the digestive tracts of bees that were encased in amber more than 25 million years ago, perhaps as long as 40 million years ago, have been found that, remarkably, or apparently not, for bacteria, were still alive! Bacteria are exceptions to the usual rules of life. They need only water to metabolize and multiply. There are strains that require no oxygen or sunlight, and those that survive in ultra-violet, that metabolize inorganic materials, like nitrogen and even iron, and volcanic gases, like sulphur, and those that survive in extreme heat and cold, beyond the extremes on the Moon, or those found around boiling deep-sea volcanic vents, all living in conditions very much like the primordial conditions on Earth, when bacteria were the only form of life.
What about a finding a glacier-frozen dino?
Glaciers don't get cold enough. Neither do the two paths taken in Cryogenic hibernation tests: chemically or temperature induced. Viable sperm is recovered from the far-colder temperatures of liquid nitrogen or dry ice to make late-term parenting a reality. Chemical tests on mice, only for less than half a day, have used low doses of respired hydrogen sulfide to dramatically lower life processes in mice, but have not been successful in more complex mammals. Tests with the temperature option, using blood-replacement technique, have shown partial, short-term, success, but those tests, and chemical-based experiments, were all of comparatively short duration and performed in tightly-controlled, laboratory conditions, not found in the wild, or the really, really wild of prehistoric times, and any frozen, prehistoric creature found would not at all be a short-term-popsicle, or char-dog-on-a-stick proposition, and would not have been kept cold enough.
Any condition that does not arrest body function would require feeding or end with death and decay, but bacterium do exist that metabolize in freezing, and even airless conditions. When Apollo 12 astronauts returned the Surveyor 3 Moon lander's television camera, which arrived on the lunar surface two-and-a-half years earlier, scientists found a strain of bacteria, known to have been in the camera when it was on the Moon's surface all that time, which, like those found inside bees preserved in amber, but using a preservation process different from spores, survived the airless space and the extreme, monthly temperature fluctuations. In fact, the substance the bacteria require to survive such conditions was courtesy of the initial bacteria, which died, producing the substance for the survival of the remaining colony! "Life will find a way ..." And, yes, the DNA of these bacteria could be cloned, and of other long-term frozen bacteria. But bacteria are not dinosaurs, and neither reptilian nor mammalian DNA has the unique, sacrificial, substance-producing, or spore-encapsulating survival capability of bacteria.
But there may be one possibility that could make the revivalist's dreams a reality. There is another, recently introduced scientific discipline, evolving into a subset of biology, called Evolutionary Developmental Biology (EDB), which incorporates new avenues of molecular-genetic research with the established research into evolutionary biology. EDB investigates the processes and the trails of genetic duplication, mutation, and regulation which determine the various changes that occur within species as evolution progresses. The process might be compared to reverse-engineering of computer software, to determine what switches and commands are used to generate subsets of actions that produce program outcomes, usually done with the goal of creating a similar program with a related purpose.
EDB, while not cloning, may lead to sufficient refinement of a process, micro-evolution, by which the prehistoric, genetic blueprint of a specie's genes can be identified and recreated, since the science examines the entire record of plant- or creature-specific genetic development that is stored within the DNA of all living creatures. Research is currently centered on genetic progressions in time, floral, germ-line, and aspects of skull evolution in vertebrates, and much work remains to be done before the state of genetic alignment of a particular species, in a certain time, can be blueprinted and the genes of the modern creature altered to match that blueprint, producing an early version of that creature's evolutionary existence. Since this would not involve original, prehistoric DNA, and would "only" require the identification of the prehistoric genetic map in a bird of today, or an earlier specimen in which DNA is still viable, and the means to recreate and grow it, it is possible that, someday, ethics and law permitting, a dinosaur could be "regressed" to life. It's not cloning, but the effect would be the same: some poor soul eventually turned into a snack at the local zoo.
But, since cloning is the process at question, it is probably a very safe bet to say that the probability of seeing living Dinosaurs, through cloning, is as good as the probability of hearing from intelligent aliens before the sun's expanding shell turns the Earth into a cinder, even though the aliens may or probably do exist, scattered throughout the vast stretches of the universe, beyond any reach of us or each other. Meanwhile, for both those aliens and the dinosaurs, there remains the safe, "imagineered" perspective of the movies.