All new finds of fossil mammoths do not let the debate about the fate of these ancient mammals cool down. Scientists are getting to the answer to the question: why did the mammoth fauna disappear?
11 species of mammoths are described, but when speaking of these animals they usually mean the woolly or tundra mammoth, Mammuthus primigenius. He had the largest range, his remains were found more often than others, and he was described first. It is believed that the environment in which woolly mammoths lived was the tundra steppe - a relatively dry area, overgrown mainly with grasses. It appeared near the glaciers, which, having fettered huge masses of water, dried up the adjacent lands. As evidenced by paleontological findings, this region was not inferior to the African savannas in terms of the abundance of various animals. In addition to mammoths, rhinos, bulls, bison, saigas, bears, lions, hyenas, horses lived in the tundra steppe. This complex of species is called the periglacial, or mammoth, fauna. But now these places are extremely poor in large animals. Most of them died out.
In the early 1990s, Russian researchers made a sensational discovery, Radiocarbon analysis of the teeth of woolly mammoths found on Wrangel Island in the Arctic Ocean showed that ancient elephants existed on this island only 3,700 years ago. The last mammoths were dwarfs, one and a half times smaller than their continental predecessors. But 12,000 years ago, when Wrangel Island was connected to the mainland, large mammoths lived there.
LOST IN SIBERIA
Discussions about the extinction of mammoths for at least 200 years. Jean Baptiste Lamarck wrote on this topic. He believed that biological species do not die out, and if animals of the past differ from those living today, then they did not die out, but turned into others. True, now there are no animals that could be considered the descendants of mammoths. But Lamarck found an explanation for this fact: mammoths were exterminated by humans, or they did not die out, but are hiding somewhere in Siberia.
For their time, both explanations were perfectly acceptable. On the one hand, the destructive effect of man on nature was already evident then. Lamarck was one of the first to thoroughly analyze this process. On the other hand, in Europe, ideas about Siberia were very vague. And it was at the time of Lamarck that data began to come in about the finds of the corpses of mammoths, well preserved in the permafrost, as if they had died not so long ago. Lamarck antagonist Georges Cuvier interpreted the same information differently: since the corpses were well preserved, they were not victims of predators, but died for other reasons, possibly due to flooding. The essence of his theory was as follows: in the history of the Earth there were transient cataclysms that could lead to a change in the fauna in a certain area.
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Around the same time, the Italian paleontologist Giovanni Batista Brocchi expressed another thought: every species on Earth has its own term. Species and groups of species are dying out, just as organisms die of old age.
All these points of view had supporters and opponents. At the beginning of the 20th century, one of Lamarck's followers, the German paleontologist Gustav Steinmann, tried to prove that only the largest mammals died out completely - those that were hunted especially intensively. The rest of the animals, known from the fossil remains, did not die out, but turned into others. Such views have not been widely accepted. Cuvier's theory of "catastrophism" turned out to be more in demand, especially since it was supported by new data on the transformations that the Earth's surface underwent during its long history.
Some researchers have developed ideas about the disharmony, "over-evolution" or "adaptability" of extinct creatures. The absurdity of individual animals was so exaggerated that the question arose: how could they even exist? Mammoths have been used as one example of such disharmony. As if the huge tusks of these proboscis, overdeveloped, led them to an evolutionary dead end. But the authors of such works bypassed one important point: "awkward" animals, before disappearing, flourished for millions of years.
And yet, their reasoning was based on a real fact: in the evolution of some groups of organisms, directions are found leading to the maximum possible degree of development of a trait. For example, the size of the body, horns, tusks, teeth, shells may increase over time. In this case, the reverse process does not occur, and when further increase becomes impossible for physical reasons, the group dies out. Austrian paleontologist Otenio Abel called this the law of inertia.
ON A SPIRIT DIET
One of the most popular hypotheses explaining the extinction of mammoth fauna is climatic. At the end of the last ice age, about 15,000-10,000 years ago, when the glacier melted, the northern part of the tundra steppe turned into a swamp, and in the southern part, forests, mostly coniferous, grew. Spruce branches, mosses and lichens became food of animals instead of grasses, which supposedly killed mammoths and other representatives of mammoth fauna.
Meanwhile, the climate had changed several times before, glaciers advanced and retreated, but mammoths and mammoth fauna survived and flourished. Suppose the tundra and taiga are really not the best place for large herbivores (however, reindeer, elk, and Canadian forest bison still live there). But the theory of evolution teaches that when the climate changes, living things must adapt to it or move. The territory at the disposal of mammoths was huge, almost half of Eurasia and most of the north-west of North America (in which, in addition to the woolly mammoth, the Colombian mammoth, Mammuthus columbi, lived at the same time).
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If the climate changed, then the number of animals could decrease, but they would hardly disappear completely. Most of the territory in which the mammoths lived is now occupied by coniferous forests and swamps, but there are other biotopes on it - meadows, river floodplains, large areas of mixed forest, devoid of forest foothills. Surely among these spaces there would be somewhere a place for mammoths. This species was very plastic and 70,000-50,000 years ago lived in the forest-steppe and forest-tundra, in swampy or, conversely, dry woodlands, in the taiga, mixed forests and tundra. Depending on the latitude, the climate in these areas varied from mild to severe.
Columbian mammoth
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But the main argument against the climatic hypothesis is that the extinction of mammoth fauna in many places occurred when significant climatic and landscape changes did not occur there. If so, the expansion of the taiga flora could not be the cause, but the consequence of the extinction of animals. If there are many herbivores, they eat not only grass, which can quickly grow, but also sprouts of trees and shrubs. As a result, trees regenerate poorly and decrease in number. In addition, proboscis can cut large trees. In African reserves, gamekeepers are forced to regulate the number of elephant herds, otherwise they simply eat the savannah. Therefore, it could happen that when the mammoths became extinct, and there were much fewer other herbivores, a forest grew on the site of the tundra steppe.
Meanwhile, it is obvious that the extinction of mammoths and other large mammals coincides in time with the beginning of the human attack on nature. Already tens of thousands lay back, people had tools with which they could destroy
their neighbors on the planet. The ability to make flint spearheads, possession of fire, the ability to hunt together and other qualities made ancient people competitors of predators.
DANGEROUS NEIGHBORS
Ancient people hunted mammoths especially often. Whole settlements were built from their skulls and skins. Maybe in the end everyone was killed? This explanation is offered by some modern researchers (although, as we said, this hypothesis is already 200 years old). Other scientists believe that "a handful of savages with sticks" were unable to exterminate a whole species of large animals.
It is not known exactly how many people there were on Earth at that time, but thousands of primitive sites have already been found in sediments 12,000 years old. Perhaps, in the days of mammoths, there were enough "savages" to cause serious damage to nature. In the 19th century, for example, European travelers described the barbaric driven hunts of Indians, Eskimos and African tribes who exterminated a huge number of animals. Moreover, the natives did not care that most of them would not be used. Huge accumulations of herbivore bones in different parts of the world indicate that ancient people did not differ from their descendants in this respect. As the fauna became impoverished, the tribes wandered away in search of places rich in game.
However, sometimes modern researchers paint a more complex picture of extermination. The man allegedly "rocked the ecological pyramids", that is, somehow violated the existing ecological order. Ancient hunters, coupled with predatory animals, allegedly first destroyed large herbivores, and then the predators themselves died out from malnutrition.
By the way, on Wrangel Island, archaeologists found traces of a Paleo-Eskimo settlement, but they were mainly engaged in marine fishing. There were no remains of mammoth bones at this site. Only the bone of a woolly rhinoceros (much earlier extinct) was found, which was probably something of a child's toy. The discovered site is 3200 years old, and the finds of the last mammoths date back to an earlier period - 3700 years ago. That is, no one bothered the last mammoths on the island, they died out on their own. The dwarf size of mammoths from Wrangel Island, as well as the imprint of disease on their remains, indicate that these animals suffered from a lack of food and closely related crossbreeding. And this small population of dwarfs gradually faded away. Perhaps it was isolation that allowed her to outlive other relatives for several thousand years.
So, the claims that climate or humans were the main reason for the extinction of mammoths are far from indisputable. In case of discrepancies in hypotheses, scientists often offer compromise solutions. There has already been a "traditional" completion of works on the extinction of animals: supposedly in this process, various adverse effects superimposed on each other. In our case, the climate damaged the mammoths, and people persecuted them, and with a decrease in numbers, genetics failed: closely related crossbreeding began, which led to degeneration. Well, let's say the mammoths were unlucky, but it is unclear why others, who were not extinct, were lucky. Bison, musk oxen, reindeer …
VARIATIONS ON THE THEME OF HAYDN
One consideration in modern science is not discussed at all, namely that mammoths became extinct "from old age." Such interpretations of evolution are now considered heresy. However, this explanation seems to put everything in its place: during the evolutionary "youth" mammoths and the climate was nothing, and primitive hunters were not afraid of them. And then, when the "youth" passed, their numbers began to decline steadily. In the end, the last long-lived populations, like the one that lived on Wrangel Island, also died out.
There is a lot of evidence of such phylogenetic aging, and their number is increasing. Recently, American researchers have traced cases of extinction of some mammals using spore-pollen analysis and many other modern methods. They concluded that in the N American continent, the disappearance of large herbivores began even before the arrival of people there and occurred gradually. The extinction of mammoths and other mammals is forming a typical pattern that paleontologists describe for older groups of animals, for example, for dinosaurs or sea cephalopods, ammonites. One of the researchers wittily compared it to Haydn's 45th Symphony, in which the musicians take turns leaving the orchestra before the end of the piece.
The aforementioned American researchers believe that the climate is the cause of the extinction. However, the facts pointed out by the founders of paleontology remain facts. For some reason, the evolution of groups of organisms goes in a certain direction, just as the individual development of an individual takes place unidirectionally - from youth to old age. The characteristics of the mechanism of "phylogenetic aging" proposed by the classics of paleontology are rather vague. Something can be clarified here if we turn to modern gerontology - the science of aging of organisms. There are several dozen hypotheses proposed to explain the mechanism of aging in an individual. They often note that some cells cannot reproduce their exact copies indefinitely. With each division, they either break DNA, or shorten the length of some sections of chromosomes,or something else that eventually leads to the impossibility of further division. It is possible that because of this, it becomes impossible to rejuvenate "worn out" cells, and therefore tissues and organs. The result is old age and natural death. Perhaps, in the whole genome, something is shortened with each copying, and this eventually leads to the impossibility of its reproduction, which means to the extinction of the species. And although today the question of the causes of extinction remains open, this last hypothesis deserves attention.and in the whole genome, something is shortened with each copying, and this eventually leads to the impossibility of its reproduction, and therefore to the extinction of the species. And although today the question of the causes of extinction remains open, this last hypothesis deserves attention.and in the whole genome, something is shortened with each copying, and this eventually leads to the impossibility of its reproduction, and therefore to the extinction of the species. And although today the question of the causes of extinction remains open, this last hypothesis deserves attention.
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If this assumption is correct, then attempts to "revive" mammoths are doomed to failure, but some scientists continue their experiments. There were reports in the media that the mammoth was about to be cloned. Japanese scientists have managed to clone mouse cells that have been in the freezer for several years, and now they seem to be ready to move on to larger-scale projects.
However, this raises the eternal question of biology: to what extent can the results of laboratory experiments on a model object be extrapolated to what happens in nature? Several years in the freezer is not thousands of years in the tundra, where the remains could thaw and freeze again many times. During a long stay in permafrost, cells cannot remain intact. Only fragments of molecules remain of them, so they cannot be cloned.
Basically, damage occurs due to the fact that the water contained in the cells crystallizes and ruptures the cellular structures. All mammoth carcasses found so far are severely damaged when compared to a mouse in a freezer. Therefore, scientists are pinning their hopes on frozen mammoth sperm. They contain very little water and can withstand freezing better than normal cells. But the probability of such a find is negligible. So for now, cloning a mammoth looks like a lost cause.
Around the World No. 8 (August) 2011