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The Labray Asphalt Pool in Los Angeles is a museum about the Ice Age. Many tourists are accustomed to seeing saber-toothed tigers throwing down horses or bison in open fields. But according to the latest research by paleontologists, this scenario is rare in the Ice Age. In fact, saber-toothed tigers prefer to hunt under the cover of forests, while giant wolves prefer to track their prey in open environments. The latest discoveries by paleontologists may also provide valuable clues as to why ancient predators such as saber-toothed tigers died out and hyenas survived.
The so-called Pleistocene Epoch can be traced back to 2.5 million years ago to about 10,000 years ago. This period includes dramatic changes in climate and the evolution of human beings to ecosystems. Labri asphalt pool is one of the best treasures of extinct Pleistocene ancient species. For tens of thousands of years, animals will sink into tar, slowly sink into pits, and eventually die of asphyxia. Over time, animal remains become fossils, and bones are trapped in harder materials. Carnivores in asphalt pools have much more specimens than herbivores, which may be because many predators are attracted to pits as they chase them into asphalt.
Labri pitch pool was discovered in 1769. To this day, scientists are constantly excavating various fossil remains from it.
Beginning in 2009, Larisa DeSantis, a paleontologist at Vanderbilt University, began studying animal fossils. Initially, she and her colleagues studied the micro-abrasion of teeth in modern animals to determine whether the abrasion reveals the dietary habits of these animals. For example, cheetahs avoid bones, while hyenas eat them. The lions behavior is somewhere in between. The pattern of tooth wear was consistent with the observed eating behavior.
Previous studies will assume that the Pleistocene has a difficult period. This hypothesis suggests that many of the carnivores preserved in the Labri pitch pond are now extinct because climate change leads to food scarcity, which intensifies competition. Because the canine teeth of the fossil puma were found to be broken, the researchers speculated that the puma had broken its teeth while chewing on the bones of dead animals. But they did not find the same phenomenon when they analyzed the teeth of lions and other Pleistocene species.
They also used the same method to study fossils excavated from the Labray asphalt pool. Desantis and his colleagues studied the tooth wear of ancient pumas and other Pleistocene species under a microscope: We found that pumas ate more like cheetahs, saber-toothed tigers more like lions, but not hyenas. No animal is munching its carcass like hell. Subsequent studies looked at the teeth of Pleistocene pumas to look for signs of their eating habits, which did show signs of foraging like hyenas, which may be one of the reasons why pumas have survived so far.
Now researchers are studying more animal fossils of teeth in order to better understand how carnivores and herbivores coexisted in the Pleistocene. Desantis and his colleagues are particularly interested in the isotopes contained in dental analysis samples because they contain all the information needed for animal diets. What you eat is what you eat, she said. Everything you eat is contained in the tissues -- the hair, enamel, nails, etc. of the predator -- but it has different isotope ratios in different parts of the body.
Previous studies of isotopes in fingernail fossils of Labri asphalt pond animals have shown that there are many overlaps in the feeding preferences of these predators, which provides more support for the hard times hypothesis. But Desantis et al. found that isotopes in teeth were not. Cats like saber-toothed tigers, lions and pumas hunt in forests, while dogs like wolves hunt bison and horses in open fields. Its not clear why the isotopes in bones and teeth are different, but Desantis says this may be related to the enamel of the latter. She said: The enamel is highly inorganic, so it is not easy to change after deposition. This makes enamel the gold standard for isotope preservation.
So can these data tell us why so many species died out at the end of the Pleistocene? Desantis said: We cant say exactly why species died out, but we can say what the consequences of species extinction are. For example, pumas and other surviving species are those that are most environmentally adapted to their predatory behavior, changing from hunting larger prey, which is becoming increasingly rare, to hunting smaller mammals. The saber-toothed tiger simply cant adapt to this. I often joke that I want to see a saber-toothed tiger bite a rabbit, Desantis said. They are not good at preying on small animals. Preying only on large prey may be detrimental to them.
Desantis is currently participating in a larger study to further clarify the respective impacts of rapid climate change and human arrival on species extinction. The advantage of asphalt pools is that they preserve animal remains very well, Desantis said. The disadvantage of Labray is that all the bones are stacked together. Unlike most fossil sites, everything in the pitch pool is mixed together.
The forthcoming study will use radiocarbon dating to date about 400 bones from different species in different pits. Researchers can then determine the exact time period of animal life and then cross-refer to the corresponding climate records. We will be able to track more accurately the ecological environment in which these animals live. Over time, as the climate changes, and as humans reach this land, we will be able to better understand the causes of extinction, at least in the Labray region, Desantis said.
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