Extinction

Extinction, a biological phenomenon consisting in the disappearance of certain species or genera of living organisms from the territory they inhabit or even completely from the face of the earth (paleontological extinction); in the latter case, extinction implies the disappearance of certain forms without their transition into other forms. Thus, completely extinct are the trilobite crustaceans, which during the Cambrian period were distributed throughout the entire globe (more than 1,700 species); they were less represented in the lower Silurian and completely died out in the Permian period. This form did not transition into any other form, and a memory of it is found only in the so-called "trilobite-like larva" of the great crustacean Limulus (tropics of Asia and America). Thus, extinct are the unique cephalopod mollusks ammonites (the so-called "devil's fingers," found near our rivers, represent the terminal parts of their shells). The causes of animal extinction are numerous; for each animal species, its own specific causes of extinction could be cited. But in general, the main cause of extinction lies in the change of those external (in the broad sense of the word) conditions in which these organisms developed and to which they adapted. Without changes in the environment, the ability to preserve species could have lasted throughout the entire paleontological history of the earth. Thus, for example, some brachiopods-Lingula, Terebratula, Rhynchonella-still live today, starting from the most ancient epochs (Cambrian, and possibly even earlier). How strongly the change in the external environment affects extinction can be seen from the replacement of one fauna by another under the influence of human activity; thus, the plowing of land in the southern steppes of the USSR forces the disappearance of the marmot there; the draining of swamps destroys wading birds, the snipe and the woodcock; the cutting down of forests-the capercaillie. The onset of the glacial period in Europe and Asia was the cause of the extinction of many animals, which survived only in places corresponding to their former living conditions; thus, rhinoceroses that inhabited central Russia now live only in Africa. On the other hand, the glacial fauna of freshwater basins has survived among us only in lakes remaining from the glacial period. The second, no less important condition for extinction is the disruption of the biocenosis (see), in which a given organism exists. The disruption of the biocenosis leads to a change not only in its quantitative but also in its qualitative composition. For example, the introduction of sparrows to the Sandwich Islands led to the destruction of almost all native bird species. The introduction of mongooses to Jamaica led to the destruction of all rats on this island. Man is one of the strong factors contributing to the extinction of many forms, either through their predatory extermination or through the change of surrounding conditions under his influence. Thus, in 1741, near the shores of Kamchatka, Bering encountered in enormous numbers the mammal-the sea cow (Rhytina Stelleri). It was hunted as game, and subsequently not a single living specimen could be found (even their complete skeletons are now considered a great rarity). According to calculations by Rothschild, 174 species of birds have become extinct or have been exterminated in historical times. In Western Europe, completely exterminated are the elk, bears, wolves, and others. Bison, which roamed the millions in the prairies of North America, in 1867 were divided by the Transcontinental Railroad into two herds-southern and northern-and in 4 years they were exterminated to such an extent that now they survive only in national parks. At present, the governments of Western European countries and the USSR are fighting this phenomenon in relation to the wisent by establishing nature reserves, proper hunting regulations, etc. In addition to changes in external circumstances and the environment, so-called internal factors of animal extinction are also assumed. Among the corresponding theories can be included the theory of the natural aging of species, analogous to the old age and death of an individual organism. An example of this kind is considered the wisent, which has survived in a small number of individuals only in the Caucasus (in the Bialowieza Forest, after its occupation by the Germans in 1916, all the wisents were killed). Despite all careful attempts to protect the wisents, their number continuously decreased. This theory, however, is very difficult to prove, and the stability of some species, living in paleontological development from the Cambrian, speaks against the universal applicability of this theory. Such a cause of an internal nature, according to some paleontologists, can also be the high specialization of organs, which prevents animals from adapting to new conditions (the so-called "victory of unspecialized"-according to Cone). Thus, many extinct Mesozoian caddis flies (Trichoptera) are much more complex and higher organized than modern ones (Martynov); Hipparion, considered the ancestor of our horse, turned out (according to new research) to be a lateral, more specialized branch than our modern horses, being in some respects more highly organized than the latter. In the Miocene, all even-toed ungulates with a special structure of legs and molars became extinct, although their origin from the five-toed Phenacodus can be traced back to the Eocene. In the Pliocene, the North American branch of horses, which did not give rise to descendants, becomes extinct. Sometimes the cause of extinction is the strong specialization of some organ to the detriment of others. Thus, the extinct predator Machairodus with huge fangs developed simultaneously with other cats, such as the tiger and lion. In all of them, there was a simultaneous development of fangs, unusually strong in Machairodus and more harmonious in other cats. As a result, the fangs of Machairodus, developed for a special purpose-attack-at the same time did not allow it to seize prey as skillfully as other cats. This eventually made it more vulnerable in the struggle for existence and led it to extinction. In addition to the causes mentioned above, one must undoubtedly also take into account the factor of infectious diseases of animals (plague, trypanosomoses, pleuropneumonia and other diseases); unfortunately, this factor has not yet been sufficiently studied.

H. Bogoyavlevsky. Extinction of peoples, a prolonged, progressive decrease in population size, leading to its complete disappearance and extinction as a special tribal group, caused by a reduction in the population's natural growth capacity. Although in many cases the decrease in the size of a tribal group is a combined process of denationalization, assimilation, extinction of language, and special forms of lifestyle, there are unquestionable cases where the decrease in size should be attributed mainly to extinction. In the USSR, ethnic groups showing a tendency toward extinction or a significant slowdown in natural growth include certain ethnic groups in the northeastern part of the European RSFSR, the extreme north, northeast, and Far East of the Asian part of the RSFSR. Comparison of data from the 1897 and 1926 censuses reveals a tendency toward extinction among a number of peoples of the USSR (with an average growth rate for the entire population of +32%) [growth rate (+), decline rate (-)]: Finnish peoples Voguls .... +24.0% Karelians . . . . +19.4% Mari.....+14.3% Ostyaks . . . . + 13.0% Lapps .... - 5.0% Mongolian peoples Kalmyks .... - 30% Buryats.....- 12% Paleoasiatics Koryaks . . Eskimos . Kamchadals Chukchi. . . Gilyaks . . Aleuts . . + 22, 7% + 17, + 6, + 6, 3, 5% 3% 3% 3% 40.0% Turks Bashkirs ... - 37.4% It should be noted the unfavorable natural growth of the Kalmyks of the Kalmyk Autonomous Oblast, who showed population stability almost throughout the entire 19th century until 1914 and a sharp decline in population level under the influence of the revolution, famine, civil war. Classical examples of extinction are: the native population of Australia, Polynesia, the Malay Archipelago, the Indian tribes of South and North America, the Eskimo aborigines of the polar regions of North America and Greenland. The Tasmanians, numbering several thousand at the beginning of colonization in the early 19th century, became completely extinct by the 1840s. The native population of Australia and a number of Polynesian islands decreased and continues to decrease at almost the same rate. In our time, the native population of the southern tip of South America and Tierra del Fuego shows a rapid decrease in numbers. Finally, the Indian population of North America has decreased by about 10 times in the last 150 years and continues to show an unfavorable growth rate. The decrease in population through extinction is directly caused by the unfavorable ratio of birth and death processes. A slowdown in natural population growth and even its decline can be the result of stable or decreasing birth rates and increased mortality. Stability of low-type reproduction can be caused by the direct influence of lifestyle traditions that enshrine in religious prescriptions the conscious limitation of birth rates (through expulsion of offspring, infanticide) and a low reproduction rate corresponding to the primitive hunting state of the people. A significant influence on the decrease in birth rates can be a decrease in fertility due to the specific effect of certain infections on the reproductive function (such as malaria) or unfavorable age-sex ratios leading to a large predominance of the male population in productive ages. The latter phenomenon of the predominance of the male population is extremely characteristic of all so-called extinct peoples of the USSR without exception. Increased mortality is caused by the excessive spread of infectious diseases, extremely unfavorable conditions of work, nutrition, climate, etc., and finally, what is especially important to note, huge losses of the native population in constant armed clashes with colonizers. The enormous spread of infectious diseases, taking the form of devastating epidemics, leads to a catastrophic decline, especially among those tribal groups that first encounter a given infection brought by colonizers; such are the epidemics of smallpox among the population of Siberia. Along with acute infections, the introduction of tuberculosis, syphilis, and other non-epidemic diseases plays a significant role in increasing mortality. Alcoholism and opium smoking should also be mentioned. In addition to the introduction of infections, the massive excessive spread of infectious and parasitic diseases (malaria, helminthiases, especially ankylostomiasis, etc.) is explained by the working, living, and nutritional conditions of the native population. Work on swampy plantations, lack of land reclamation, lack of water supply protection, etc., some non-infectious diseases, such as nutritional deficiency diseases (avitaminosis), find a similar explanation. However, there is no indication of the existence of special racial diseases—the excessive mortality of the native population from a number of infectious and other diseases is not the result of racial inferiority. Europeans, first encountering colonial conditions, also show a similar tendency to increased morbidity and mortality with respect to a number of endemic diseases (malaria, yellow fever, etc.). The basis of extinction processes are socio-economic causes, which in turn are a consequence of colonial-imperialist policy. These causes should include the displacement of natives from their permanent places of residence, from their areas of economic activity, the compulsion to slave labor, and the continuously progressive deterioration of living conditions as a result of colonial oppression policies. On this basis, the appalling sanitary condition of the population is created, which directly causes extinction. How the extinction process is determined not by racial but by socio-economic causes can be particularly clearly seen from the example of the extinction processes of the peoples of Siberia. Researchers (Patkanov and others), who developed material on the growth of the indigenous population of Siberia based on 19th-century data and the 1897 census, came to indisputable conclusions about the dependence of population growth and extinction processes on the socio-economic structure. Negative population growth is characteristic of peoples standing at the most primitive stages of economic development (hunters, nomads, reindeer herders). Already a mixed livestock-farming group gives stability of growth, and a purely settled agricultural group gives sufficient positive growth. Peoples of Siberia belonging to the same tribal group but different in their economic structure (Yakut reindeer herders, Yakut farmers) show different types of growth corresponding to this structure. The Kalmyks of the Astrakhan steppes show extremely unfavorable fluctuations in population growth in parallel with the general, sharply expressed instability of the livestock economy of the region. Finally, the political conditioning of the direct physical destruction of the population needs no explanation. From this it follows that extinction is not an irreversible process, that it can stop and then be replaced by a regenerative process. Already the relatively short period of existence of Soviet national policy has given tangible results in improving the sanitary condition and eliminating the extinction process of a number of peoples of the Soviet Union. The struggle against extinction is the struggle for a painless transition from lower, dying-out forms of economy to higher ones, the struggle for raising the level of general and sanitary culture, for the final destruction of the remnants of lifestyle traditions. All this, of course, can be achieved on the basis of full national independence and the destruction of colonial-imperialist oppression.