MOSCOW , March 6, Nikolai Guryanov. Biologists from Moscow have proposed a new classification of living organisms. Their concept cancels the concept of a species, which is fundamental in zoological systematics. Why is this important not only for science, but also for relations between people?Not everything is so simple
Scientific classifications are artificial and natural. Artificial ones are created by man for special tasks. For example, in order to release the Red Book, it is necessary to divide animals into endangered, rare and widespread.
At the same time, scientists are trying to develop so-called natural classifications — that is, to describe the systems that actually exist in nature. One of them is Mendeleev's periodic table.
It is more difficult to create such a harmonious system in biology. Thus, the classification of organisms is a serious problem. =»600″ data-crop-height=»600″ data-source-sid=»cc_0″ class=»lazyload» width=»1920″ height=»1920″ decoding=»async» />
The evolution of living beings can be represented as a genealogical tree. With the upper ranks, everything is more or less clear. All living organisms are divided into domains — archaea, bacteria and eukaryotes. The latter, in turn, are divided into several treasures. One of them — posterior flagella — includes the kingdoms of fungi and animals. Further down the hierarchy are class, order, family, genus and, finally, species.
The further down the hierarchy, the more scientists argue about each particular taxon, its content and boundaries. The most problematic step is the last one. Science still does not have a generally accepted definition of species.
“A two-legged creature, without feathers, with flat nails”
The ancient Greek philosopher Plato defined a person as “a bipedal creature, devoid of feathers and with wide (sometimes flat) nails, receptive to knowledge based on reasoning”. This is a classic example of the so-called typological or morphological description, in which a species is defined by a set of external features inherent in it.
Carl Linnaeus, who is considered the founder of a unified classification system for flora and fauna, could only use the “eyeball method” — that is, a visual assessment.
With the development of tools, science has many other ways to determine a species. It turned out that some populations of animals, similar in appearance to the degree of indistinguishability, are completely different at the genetic level. For example, it was established that African elephants are not one species, but two: savanna and forest.
The modern definition of a species, which is taught in Russian schools, is as follows: “a set of individuals capable of interbreeding under natural conditions with the formation of fertile offspring, inhabiting a certain area, possessing a number of common morphological, physiological and other signs.”
However, none of these criteria can be considered absolute. In particular, the ability to interbreed and produce fertile offspring. For example, there are so-called ring types. These include the sea gulls, settled throughout the Northern Hemisphere. Each species of these birds can successfully interbreed with a living one, but with its neighbors it no longer has neighbors.
In total, more than 30 concepts of understanding species are named. Some taxonomists reject this unit of natural classification in principle and only recognize the existence of individual individuals.Russian scientists Alexander Martynov from the Zoological Museum of Moscow State University and Tatyana Korshunova from the Institute of Developmental Biology of the Russian Academy of Sciences have proposed a new look at the classification of living organisms. Their work has been published in the well-known Cambridge University book series «Special Volumes of the Systematics Association». The authors of the work argue with the understanding of the species as a constant. They suggest that when describing each organism, ontogeny should be taken into account — that is, its life cycle.
“There is such a thing as a phylotypical period, when embryos of completely different animals show a high level of similarity,” says Martynov. — For example, a frog, a bird and a person have a stage of development in which they all resemble a fish. This suggests that all three groups of animals had a common fish-like ancestor.»
Ontogenetic conservatism and its connection with the ancestral organization are confirmed by modern molecular methods, the scientists note.
In previous works, the co-authors showed the presence of the same conserved stages in invertebrates (only the common ancestor was, of course, different). Scientists now argue that the same approach can be extended to at least all multicellular organisms. Martynov and Korshunova proposed to make the conservative stages of ontogeny the basis for filoperiodic tables, which vaguely resemble the periodic table of Mendeleev. is clearly defined quantitatively. In biology, everything is an order of magnitude more complicated,” Martynov notes.At the same time, scientists propose to take into account not only genetic, but also epigenetic factors. Evolution occurs constantly during the life of each organism. Thus, recent studies have shown that people whose ancestors survived the siege of Leningrad or the Holocaust bear a special epigenetic mark. That is, the stress was so strong that the trace of it was preserved for several generations.
In another study, laboratory mice were given to smell a certain aroma, and later it turned out that their offspring were more sensitive to the source of this smell. That is, this group of creatures began to differ from the original.
But the existing taxonomy does not take into account epigenetic changes. 1825191169.html» data->
Russian scientists offer a description of an individual organism or group in the form of a formula that would resemble the formula of a chemical compound, but at the same time would retain continuity with the traditional nomenclature. At the same time, the traditional binary name (for example, Homo sapiens) becomes the core of the new conditional notation.
Such a formula for the multilevel diversity of organisms (Multilevel Organismal Diversity, MOD), as the authors of the concept call it, should take into account both a common evolutionary origin and recent changes in a small group or individual.
Martynov believes that such an approach will be a «cure for racism.» The imaginary superiority of one race over another is often justified by the fact that they supposedly represent different «species» or some other «groups». But it will be difficult to say if, in the words of a taxonomist, «everyone, without exception, bears signs of bacteria, invertebrates, fish, archaic hominids and many other organisms.» That is, the ontogenetic approach emphasizes that each living organism does not just belong to some «strictly diagnosed group», but carries a true multi-level diversity, including the features of the most distant and closest ancestors.
The new work does not offer a complete code of the new nomenclature, but only the basis for its creation. Scientists acknowledge that the development of a new classification will be associated with many difficulties and will require many years.
The authors of the work are completely convinced of the need for such efforts. Martynov compares the existing biological classification with Newtonian pre-relativistic physics, which could not explain some cosmic phenomena. In his opinion, we will not understand what real diversity is if we stick to a rigid concept of species.