You can, you can…

Is it necessary to resurrect extinct species? 

Kirill Stasevich, "Science and Life" No. 6-2017
Published on the website "Elements"

At the end of February this year, the pages of many scientific and popular scientific publications were literally covered with herds of mammoths: the outstanding geneticist and chemist George Church, known for his work in the field of molecular biology, said that he and his colleagues in the next couple of years will be able to resurrect a woolly mammoth, which, as is known, it became extinct about 10,000 years ago. Mammoths are one of the most charismatic animals that have ever lived on Earth. However, many biologists, commenting on the upcoming "resurrection" of the mammoth, advised to first decide how and why we are going to do it.

First about how. Every biological species has more or less close evolutionary relatives. Closely related species are more similar to each other than distant relatives. In this case, we can combine the genetic portrait of an extinct species from those genes that remained in its immediate descendants and related species that have survived to our time. Here the methods of classical genetics are suitable, which boil down to the fact that we cross animals, and then analyze the signs that have fallen into the offspring, and select among the offspring those individuals that are most similar to the extinct species we are interested in. For example, if you try to breed mammoths from Asian elephants, then you need to purposefully select the most hairy individuals in each generation (of course, hairiness is not the only sign that distinguishes elephants from mammoths). But in this case, there will still be significant admixtures of modern species in the genome, and what we get will be only a version of an extinct animal, more or less close to the original.

Molecular biology allows you to manipulate genetic material directly: you can extract DNA from the remains of the same mammoth, compare it with The DNA of the current elephants and thus understand what needs to be done with elephants so that they become mammoths. Then the methods of genetic engineering come into play: by editing the necessary genes in the elephant's genome, we will get someone very, very similar to a mammoth. Genetic engineering allows you to perform the same task faster than crosses, and the result should be much more convincing.

Editing does not necessarily imply a large-scale rearrangement of the genome. For example, if we recall another extinct species, the wandering pigeon, which was completely exterminated by the beginning of the XX century, then its genome is 97% indistinguishable from the genome of its closest relative, the striped–tailed pigeon, which is safely alive to this day. That is, the DNA of both pigeons differs by only 3%, and among these 3% there are several thousand mutations that determine the differences between the species. And already out of several thousand, several dozen really key genetic features can be identified that make a wandering pigeon a wandering pigeon, and a striped–tailed pigeon a striped–tailed pigeon. And, going to reconstruct an extinct species, you only need to understand which mutations are considered truly necessary.

George Church and his team of "mammoth rescuers" claim that they have managed to introduce as many as forty-five mammoth modifications into the genome of the Asian elephant (the closest evolutionary relative of the woolly mammoth), some of which should provide the elephant with mammoth wool and a thick fat layer. However, the question is not limited to these forty-five alone: a number of mammoth features will need to be introduced into elephant DNA, after which it will be necessary to check how such a hybrid genome behaves in cells, whether modified and unmodified genes conflict with each other. The researchers expect that they will be able to do all this in two years. However, do not wait for a ready-made mammoth by 2019-2020. Everything that Church and his team have done, they have done so far only on DNA molecules. Then you will need to do genetic editing with an elephant embryo, transplant it to a surrogate mother and hope that its development will go well. Considering that many embryos die during such manipulations, it is hard to believe that it will come to the point here at all: the Asian elephant is classified as an endangered species, and it is unlikely that it will be possible to get a sufficient number of its embryos for molecular and cellular experiments.

But let's imagine that all the technical difficulties have been overcome: we calmly make any changes to the genome and in any quantity and we have no shortage of biological material. And here there are difficulties of a higher order, evolutionary and ecological. Firstly, one mammoth that has risen from oblivion is not yet a species, it is just one individual. To resurrect a whole species, you need a lot of mammoths, they have to live on their own and reproduce themselves. Now let's recall one of the basic rules of evolution: the population of a species must have a fairly wide genetic diversity. Living creatures live in a highly variable environment, and how well they are adapted to it depends on genes. Abrupt changes in the environment for an individual can end badly, but in general the population will survive, because among its members there will be those whose gene variants allow them to survive in new circumstances.

Although it may be that they will not be found. If the entire population consists of individuals with very, very similar gene variants, and the environment around them is very, very changeable, then nothing good can be expected. A viable population should include hundreds and thousands of individuals with individual genetic sets, and only when we have such a population (or even better, several), we will be able to talk about a "resurrected" species.

This is firstly, and secondly - where exactly are we going to resurrect the selected species? After all, it once existed in a certain ecosystem and was associated with other species that surrounded it at that time. Now everyone understands that it is impossible to engage in some kind of activity taken separately from others. If we look away from mammoths and remember about modern animals that are threatened with extinction, then earlier ecologists tried to preserve them in this way – consistently and most often starting with those who occupy the lower stages of the food pyramid. There is a reason for this: it seems obvious that if we increase, for example, the number of fish in the ocean, then the number of seals that feed on it will increase by itself. However, now it is increasingly being said that it would be more reasonable and effective to try to preserve species comprehensively. This, in particular, is discussed in one of the recent articles in Nature Ecology & Evolution, the authors of which showed on a mathematical model that by taking measures to preserve both the predator and its prey at the same time, it is possible to achieve an accelerated increase in the number of both, rather than trying to preserve them in turn.

Regarding the extinct species being restored, this means that if we undertake to resurrect some dinosaur, we must simultaneously provide it with a whole Jurassic park with a crowd of relatives so that it has a place to live, what to eat and with whom to reproduce. Well, let it not be a dinosaur, let it be a mammoth – but a mammoth is unlikely to feel at home in the current ecosystems. Therefore, when thinking about what kind of species we would like to restore, it is best to choose one that has recently died out and for which there are still ecosystems where it could be integrated.

Finally, according to a number of ecologists from Australia, Canada and New Zealand, instead of engaging in the "resurrection" of extinct species, it is better to focus their efforts on those that have not yet become extinct, but which are definitely threatened. In an article in Nature Ecology & Evolution Joseph Bennett (Josep Bennet) from Carleton University (Canada) and his colleagues analyze the costs that will be required in order to maintain the resurrected extinct species in a "living" state. The researchers are discussing the conservation of the species, not one or two or three individuals; in addition, there are no costs for molecular biological operations in their calculations - the authors of the work wanted to estimate only the ecological cost. At the same time, they compared similar species, that is, the ecological price of a mammoth was correlated not with the cost of some squirrel, but with the cost of an Asian elephant.

The money that different countries spend on ecology is either public or private. Nevertheless, regardless of the source of funds, it is better to spend them on something that has not yet disappeared. According to the authors of the work, if the funds that are supposed to be allocated for the "resurrected" species are directed to the preservation of those who have not yet died out, then we will be able to save 2-8 times more species. (Once again, we recall that funds for the actual "resurrection", that is, for molecular biological, embryological and other procedures, are not taken into account here.) The sustainability of any ecosystem directly depends on biodiversity, that is, on whether there are many different species of living creatures living in it. If we take into account that ecosystems are intertwined and that these are not only wild forests and sea depths, but also agricultural territories and cities, then it is clear that the greater the biodiversity, the better for ourselves.

So the answer to the question of whether it is necessary to resurrect extinct species is no, it is not necessary. Now environmentalists have more pressing tasks that would be worth spending our so far limited resources on. But if we are not talking about a species, but about an individual, then it is definitely worth continuing the "resurrection" efforts in order to better understand how various genomes are arranged, how they evolved and how the "obvious" evolution that we observe with our own eyes in the form of a change of living forms on Earth is connected with the evolution of the "invisible", occurring at the level of molecules and cells.

Portal "Eternal youth" http://vechnayamolodost.ru 25.08.2017