Dinosaurs have captivated the imagination of people across generations since the the word was first coined in the late 19th century by Sir Richard Owen. Over the next century dinosaurs became part of the pop-culture, featuring in many stories, novels and movies. Of course, the most famous examples being Michael Crichton's Jurassic Park and The Lost World which were adapted to movies by Stephen Spielberg and were box office hits.
These books/movies garnered public attention on an unprecedented scale because they popularized the idea of reviving dinosaurs through genetic engineering and cloning. If scientists were to clone dinosaurs and bring these former rulers of the Earth back to life, it would probably be one of the greatest scientific feats of all time. But can we really clone dinosaurs? Do the things shown in Jurassic Park make sense? Let's take a look at the possibilities of cloning dinosaurs, and what obstacles scientists are facing in doing so.
One of the most popular ideas behind cloning dinosaurs is finding a mosquito fossilized in amber which still has dinosaur blood preserved in it. How would this happen? Let's consider a mosquito which has just fed on dinosaur blood. Soon after, the mosquito sits on a part of tree with tree resin (and not sap as commonly misinterpreted). As the mosquito gets stuck in the resin, it tries to fly out of it, but soon it's engulfed by the sticky resin and dies. The tree eventually dies and over millions of years it becomes part of the coal deposit. The resin with our mosquito is slowly polymerized and thus hardened into amber with the mosquito perfectly preserved in it.
Now, millions of years later this mosquito is discovered by a team of enthusiastic scientists. And they also discover that the mosquito has dinosaur blood in it. It seems pretty simple from there on. Extract the blood, and then the DNA from it. Fill up the gaps in DNA with an extant species such as frog. Then get an ostrich egg before the hard shell is formed and replace the ostrich DNA in the egg with the modified dinosaur DNA. And voila! We have a cute little T-Rex running around in no time.
Reality is, genetic engineering does not work like this and cloning a dinosaur would be near to impossible. Finding organisms in amber is pretty common in paleontology. However finding a mosquito with dinosaur blood in it is a tough probability. Furthermore, even if this kind of specimen is found, it will be highly improbable that the blood has not been mixed with blood of other creatures, that is, the mosquito did not consume blood from other creatures before or after snacking on a dinosaur. And if we are lucky enough to find a pure specimen, we have a host of other serious obstacles.
Let's consider that the mosquito perished immediately after sucking dinosaur blood. But its stomach acids would keep digesting the blood (and the DNA with it). Furthermore, the DNA would be further contaminated with bacterial, viral, and even the mosquito's own DNA. That is the least of the problems. For the sake of argument, let's say the scientists are able to extract and amplify the dinosaur DNA using PCR (PCR is a technique scientists use to replicate entire strands of DNA from very small samples).
Technically speaking, the DNA must be complete for any chance of cloning and must not be contaminated with any other forms of DNA. What does this mean? DNA is made up of between 1-10 billion base pairs. The largest quantity of prehistoric base pairs found so far is around in the tens of thousands region, but this is from fossilized bears as recent as 40,000 years old. It will be very hard to find anything close to that from 65 million years ago to say the least. And of course scientists do not know the exact sequence of dinosaur DNA, infact, they have no clue. This is because there is no living dinosaur DNA to compare the ancient DNA sequence with.
The closest scientists can get is compare it to birds (the only living descendants of dinosaurs) and other reptiles such as lizards, frogs, and crocodiles. This will not however result in even nearly coming up with the correct sequence of dinosaur DNA as they are a different species and belong to their own superorder altogether. It will be beyond optimistic to say that scientists will be able to complete these DNA sequence with bird or crocodile DNA as they don't know dinosaurian DNA sequence to begin with. And when it comes to cloning, knowing the DNA sequence is most essential, without it, cloning will not be possible.
Moving on, let's say our scientists decide to fill up the gaps in the dinosaur DNA sequence using crocodile or bird DNA. If they are successful, it will still not result in real dinosaur as the DNA is an altered version of the original. Considering the scientists are able to complete a pseudo-dinosaurian DNA sequence, the next step would be a viable medium for this to grow.
This would most probably be done by injecting the dinosaur DNA into the the nucleus of a fertilized egg cell of a close living relative such as an ostrich and replacing the original ostrich DNA in the egg. However, the development of the embryo in that egg would be regulated by the hormones and environment within the egg itself.
In the end if all these seemingly impossible barriers are somehow overcome to make a dinosaur, it will be almost impossible to sustain it. For starters, herbivores would not be able to survive at all as plants are constantly evolving to develop poisons and other protective measures against predators. The chemical composition of plants today would be very much different from that 65 million years ago and herbivore dinosaurs would find it extremely hard (if, at all) to survive on modern day plants.
Carnivores are a different story though, as the chemical composition of flesh and meat has not changed much over the millions of years of evolution. If however, this obstacle is overcome, there is another huge one awaiting. That, is of microbodies. Bacteria and viruses will pose the biggest threat to a newly cloned dinosaur, as these microbes have changed and evolved drastically over the course of time.
We are finding new microbes and diseases everyday, and often our immune system finds it hard to fight microbes, even though it is 'up-to-date'. Imagine how a dinosaur's 65 million year old immune system that has been reproduced would fare against modern day microbes. The chances of survival would be, if any, are extremely slim.
It would be amazing if we could see these creatures come to life. No other creature has dominated our planet like the dinosaurs. They were the rulers of the Earth for over 165 million years. Their sizes, shapes, and sheer variety of species make them even more attractive to us and thus make us so much more curious about them.
However, it seems unlikely that atleast in the foreseeable future, dinosaurs could be cloned and brought to life. The barriers to cloning a dinosaurs are innumerable and only a few important ones have been mentioned in this article. For now, we will just have to be content with dinosaurs in our imagination, and in movies and books such as the Jurassic Park.