Long-range fantasies
Will science ever be able to revive dinosaurs?
Alexander Markov, "Elements"
Unfortunately, science is still very far away from this. We haven't even revived the mammoths yet, although it's much easier.
Firstly, the last mammoths lived not very long ago: live mammoths walked on Wrangel Island only 4000 years ago! Frozen mammoth remains have been preserved in the permafrost, from which DNA can be extracted. The mammoth genome has already been read (that is, the sequence of letters-nucleotides in the mammoth genome is already known, in which the program for the development of a mammoth from a fertilized egg is encrypted). Moreover, whole cell nuclei can be extracted from frozen mammoth tissues and transplanted into the egg cell of another mammal. Such experiments have already been conducted with mouse eggs. At the same time, mammoth cell nuclei even show weak signs of life (K. Yamagata et al., 2019. Signs of biological activities of 28,000-year-old mammoth nuclei in mouse oocytes visualized by live-cell imaging)!
Secondly, we have living very close relatives of mammoths – elephants. Therefore, in general, it is clear who could bear a baby mammoth that would develop from an elephant egg with a mammoth genome embedded in it: an elephant could. But there are still many technical problems that can be solved in principle, but science still needs to develop for a long time before they are fully solved.
It's much worse with dinosaurs. The first difficulty is the absence of living close relatives of extinct dinosaurs. Of course, except for birds, which not only descended from dinosaurs, but are themselves conditionally considered dinosaurs (according to modern formal rules of biological classification). But after all, we are not interested in birds, but "real", ancient flightless dinosaurs like diplodocus or Tyrannosaurus.
However, biotechnologies are developing so fast now that we can actually hope that in the foreseeable future scientists will learn how to grow, for example, goslings in a chicken egg. And there it's not far from the dinosaurs. So the problem of "surrogate mothers" (or "surrogate eggs") does not look completely insurmountable.
The situation is much worse with another problem. We have neither genomes, nor, moreover, living dinosaur cells. The last real ("non-bird") dinosaurs became extinct 66 million years ago. DNA can't last that long. At least today, scientists are almost sure that it can't. Even if we are incredibly lucky and we still find exceptionally well-preserved dinosaur fossils that contain pieces of ancient dinosaur DNA, these pieces will probably be very small and few. We will definitely never collect the complete genome of a dinosaur from them. This is the main difficulty.
At first glance, it seems insurmountable. But don't underestimate the possibilities of science! You can look for workarounds. Comparative genomics is developing very rapidly now – the science of the structure and evolution of genomes. It already allows us to say something about the genomes of long-extinct animals based on the available knowledge about the genomes of their modern descendants. For example, having the genomes of modern birds, in principle it is possible to restore (albeit only partially and very approximately) the sequence of letter-nucleotides in the genome of their last common ancestor – that primitive Mesozoic bird from which all modern birds descended.
Another rapidly developing science, evolutionary developmental biology, is trying to understand how different genes affect the development of an organism and how evolutionary changes in genes lead to changes in the structure of the organism.
It is hoped that together these two sciences (of course, if everything goes well and they continue to develop rapidly for several more centuries) will develop methods for designing genomes and artificial breeding of animals that do not exist on Earth today. These may include animals similar to extinct dinosaurs. Although, of course, it will probably never be possible to truly resurrect any particular "non-avian" dinosaur that did not leave living descendants in this way. Because we will never know the exact sequence of nucleotides in his genome. But artificially engineered animals resembling dinosaurs may someday be born.
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