Animal growth is limited, particularly for terrestrial animals. The square-cube rule is the basis for this.
The Argentinosaurus, a titanosaur that weighed 77 tons (70 metric tons) and lived about 90 million years ago during the Late Cretaceous, was most certainly the largest animal to ever move on Earth. In contrast, the African elephant (Loxodonta), which weights less than 7 tons, is the heaviest animal on earth right now. (6 metric tons). The blue whale (Balaenoptera musculus), which weighs an estimated 165 tons (150 metric tons) on average, may be the largest mammal to have ever existed. They both appear exceedingly dainty in comparison.
Could a mammal ever surpass that, though? Is there a size restriction for animals?
According to Geerat Vermeij, a professor of geobiology and paleobiology at the University of California, Davis, “we look at blue whales, and the question is whether we could get anything bigger.” Vermeij made this statement to Live Science. “I’m unsure of my willingness to refuse that request. Numerous variables affect size, and I adopt a liberal viewpoint.
According to Felisa Smith(opens in new tab), a professor of paleoecology at the University of New Mexico, there may be a hard limit for terrestrial creatures of about 120 tons (109 metric tons) imposed by the rules of physics. She explained in an email to Live Science that if you were larger than that on land, your thighs would need to be so broad to support your weight that you couldn’t move around with ease. Smith is alluding to the square-cube rule, which was first defined as “the ratio of two volumes is greater than the ratio of their surfaces” by Galileo Galilei. To put it another way, larger animals require much larger appendages to support their weight because as an animal gets bigger, its volume expands more quickly than its surface area. The square-cube rule states that an elephant would collapse if we simply scaled it up by a few orders of magnitude because its bulk would increase by a power of three while the size of its extremities would increase by a power of two.
Animal growth is, however, not only limited by mechanics. If it were, we would inhabit a planet filled of 100-ton land animals while meticulously following Galileo’s cube-shaped rule. Megafauna need to consume, so the abundance of resources is another important consideration. According to Jordan Okie(opens in new tab), a quantitative biologist at Arizona State University, animals that exist in more fruitful habitats and eat high-quality food can typically support bigger maximal body sizes. Whales, elephants, and other megabiota frequently inhabit nutrient-rich, fruitful habitats.
According to Smith, the need for nutrients explains why reptiles like titanosaurs came to be much bigger than even the biggest terrestrial animals. Warm-blooded animals need about 10 times as much sustenance as reptiles do to maintain a particular body size because they have faster metabolisms, according to Smith. Reptiles, on the other hand, can afford to consume less and can develop on a calorie diet that would starve an animal because they have lower body temps and slower metabolisms.
Not unexpectedly, Smith noted, the biggest terrestrial dinosaurs were roughly 10 times larger than the largest animals.
Several of these laws are obviously broken by warm-blooded animals like blue whales, which can weigh up to 165 tons. However, their specific setting accounts for their achievement.(opens in new tab). Marine megafauna can develop in ways that would cause the appendages of land animals to disintegrate by taking advantage of their buoyancy to scale up in size without putting undue pressure on their muscles and bones. Additionally, whales can move over kilometers of open water in search of food.
Animals that live in water “are expected to be less constrained by biomechanical constraints,” Okie wrote in an email to Live Science. For creatures that are movable and resourceful, the seas also provide an abundance of nutrient-rich resources. Okie added that the development of baleen plates in particular made it possible for whales to effectively ingest zooplankton in order to sustain their huge sizes.
Despite some obstacles, it is obvious that the earth can sustain megafauna. Megafauna have existed for hundreds of millions of years. Megafauna, however, have virtually disappeared over the past 20,000 years(opens in new browser), a brief blink in evolutionary time. A number of groups of marine megafauna, like whales, are constantly teetering on the edge of extinction. This includes large terrestrial animals like elephants and rhinos, which are only found in certain regions of the globe. So, where did all the titans disappear to?
Most were exterminated by humans, according to Vermeij. We have probably exterminated 90% of all big creatures, and definitely all of the larger ones, including mammoths, elephants, bison, and large predators. The main barrier to the resurgence of these big animals is humanity. Megafauna couldn’t return unless there were no people, according to Vermeij. “We are by far the dominant species, and under our rule, no animal will grow to be very big. It’s doubtful that anything as large as a Cretaceous monster will ever exist again.
