Perhaps the largest animals that ever walked the earth were dinosaurs Argentinosaurus, a 77-ton (70 metric tons) titanosaur that lived about 90 million years ago during the late Cretaceous period. For comparison, the heaviest animal on Earth today is Africa Elephant (Loxodonta) weighing less than 7 tons (6 metric tons). And they both look positively cute blue whale (muscles of Balaenoptera), which, with an average weight of 165 tons (150 metric tons), was probably the heaviest animal that ever lived.
But can any animal handle that? Is there a limit to the size of the animal that can be reached?
“We saw blue whales, and the question was whether we could achieve something bigger.” Gerath Vermige (Opens in a new tab), professor of geology and paleobiology at the University of California, Davis, told Live Science. “I’m not sure I’m going to refuse that question. Size depends on so many factors, and I take a relative viewpoint.”
Although, in theory at least, there could be a hard limit – enforced by the laws of physics – of around 120 tons (109 metric tons) for wild animals, according to Felissa Smith (Opens in a new tab)Professor of paleoecology at the University of New Mexico. “To get any bigger than that, on Earth, your feet would have to be so wide to support your body that you couldn’t walk efficiently,” he told Live Science in an email.
Smith pointed out Square cube law (Opens in a new tab), a mathematical principle first described by Galileo Galilei as “the proportion of two volumes is greater than the proportion of their surfaces.” In other words, as animals get bigger, their volume grows faster than their surface area, so larger animals need bigger limbs to support their weight. If we only increased the size of an elephant by a few times, the cube-square law would say that it would collapse — its mass would increase by a third power, while its limbs would increase in volume by a second power.
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The only way our large elephants can overcome this limitation is by having disproportionately large and thick feet. But even then, at around 120 tons, the limbs needed to keep an elephant afloat would be enormous. The largest animal in the fossil record weighs just under 100 tonnes [90 metric tons], which supports this theoretical maximum,” said Smith, adding that “it is not clear that larger companies cannot evolve.” “
But physics isn’t the only limit to animal size. If so, we would live in a world full of 100 tons of wild animals, and play carefully with Galileo’s cubic strains. The availability of resources is also an important factor – megafauna have to eat. “Animals that live in more productive environments with higher quality food are generally able to accommodate a larger maximum body size,” he said. Jordan Aoki (Opens in a new tab), a quantitative biologist at Arizona State University. “Whales, elephants and other plant myiabiota tend to live in environments that are productive and rich in nutrients.”
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Nutritional needs also explain why reptiles, such as titanosaurs, grew much larger than even the largest land mammals, according to Smith. Smith explains that because warm-blooded mammals have faster metabolisms, they need about 10 times more food to support a given body size than reptiles. Reptiles, on the other hand, have lower body temperatures and slower metabolisms, so they can eat less and can grow on a caloric budget that would starve mammals.
“It’s not surprising that the largest land-dwelling dinosaurs were about 10 times larger than the largest mammals,” said Smith.
The blue whale, which can weigh up to 165 tons and is a warm-blooded mammal, is a striking exception to many of these rules. But hmm Their unique environment explains their success (Opens in a new tab). Megamarines can use their buoyancy to increase in size without straining their muscles and bones, and they grow in ways that would cause land animal limbs to collapse. And whales have miles and miles of open ocean at their disposal, which they traverse in pursuit of their food.
“It is hoped that animals in the water will be less constrained by biomechanical constraints,” Oakey told Live Science in an email. “Oceans also provide abundant and nutrient-rich resources for these active and resourceful animals.” Oki adds that the evolution of the baleen plates in particular allows whales to consume zooplankton efficiently enough to support their large size.
Limitations aside, the planet can definitely support megafauna. For hundreds of millions of years, megafauna were widespread. However, for the past twenty thousand years or so (Opens in a new tab), Just a blink of an eye in the time of evolution, the megafauna was almost extinct. Large land mammals such as elephants and rhinos are in decline, and are found only in certain parts of the world; Many marine megafauna groups, such as whales, continue to teeter on the brink of extinction. So where have all the giants gone?
“Most of them were wiped out by humans,” Vermeig said. “Mammoths, elephants, bison, large carnivores – we have eradicated 90% of the large animals, maybe more, of course all the large animals.”
Humans are also the main obstacle to reviving this large species.
“You don’t have to have humans before megafauna can come back,” Vermeig said. “So far, we are the dominant species, and no animal will grow under our domination. The possibility of getting anything the size of a Cretaceous dinosaur again is out of the question.”
