Why did dinosaurs grow so big?
1 Flourishing vegetation contributed to the "mega-mega-ization" of dinosaurs.
During the Mesozoic period, which began in the Triassic period, 250 million years ago, to the Cretaceous Period, when the dinosaurs became extinct 65 million years ago,
The earth's atmosphere contains much more carbon dioxide than it does today, which means that the global climate was much hotter then than it is now (if you pay a lot of attention to global warming, you know that the increase in carbon dioxide levels is directly related to global warming).
The high levels of carbon dioxide in the atmosphere (converted into food through plant recycling) and higher temperatures meant that the prehistoric earth was covered with a wide variety of plants, including trees, mosses, etc. The dinosaurs who dominated the earth were like children facing huge natural dinner cabinets, and they must have struggled to resist the temptation of delicious food. In this way, dinosaurs can grow so large, perhaps only for a simple reason, and that is overnutrition. This also explains why carnivorous dinosaurs are not far behind in size. Imagine a 23-kilogram carnivore, when confronted with a 10-ton herbivorous animal.
2 A form of self-defense for a massive dinosaur.
If you think inference 1 is too simplistic, then your intuition is probably right. A large amount of vegetation alone does not determine the evolution of organisms to "mega-belittle", and many of the flaws of "mega-magnity" (such as affecting the speed of action and limited group size) can easily offset the benefits of food access.
Still, some paleontologists argue that the evolutionary advantage of "megasity" brought many benefits to dinosaurs, and that the huge herbivores did not have to worry about being attacked by predators. This theory also provides evidence for the inference that Tyrannosaurus rex (Tyrannosaurus rex) was a scavenger: the bewildered dragons that the tyrannosaurus used to feed on it usually died of disease or old age, rather than being killed by the tyrannosaurus rex.
3 Dinosaur "megasity" is a byproduct of "cold-blooded".
The reasons for the "megacity" of dinosaurs may be even more complicated. Many paleontologists who study giant herbivores believe that dinosaurs were cold-blooded. They had two more convincing reasons: first, according to our metabolic patterns today, a warm-blooded lepidarosaur would be roasted quickly from its body like a potato and die; second, no mammal living on Earth today could grow as big as a herbivorous dinosaur, the largest of today's land animals, but only a few tons in weight. Scientists believe that cold-blooded herbivores evolve to a certain size and will achieve a "constant temperature" effect, that is, the ability to maintain the temperature of the body. This is because a cold-blooded animal the size of a house will have a very slow process of raising its body temperature in the sun and falling at night. This enables it to have a relatively constant average body temperature.
How long did dinosaurs live?
Fossilized skeletons of dinosaurs that lived 100 million years ago tell us many of the stories of its life, such as what it ate, how it walked, how it interacted with other of its kind, but it didn't tell us how long it would live. In fact, to know the lifespan of sauropods or tyrannosaurs, one must first have a large amount of research evidence, including analogue analysis based on the lifespans of modern reptiles, birds, and mammals, analysis of how dinosaurs grew and metabolized, analysis of dinosaur skeleton fossils, and so on.
These kinds of studies can help determine the cause of death of dinosaurs. Paleontologists can speculate whether the unfortunate dinosaur was buried by an avalanche, flooded, or suffocated in a sandstorm based on the location of a dinosaur's fossil; they can also speculate whether it was hunted by other predators based on the traces of gnawing on the iliac (of course, it is not excluded that it was eaten by scavengers after it died of natural causes); if it can be determined that it is a young dinosaur, then the cause of old death can be excluded, but it is impossible to judge whether it died of disease. Because so far scientists know very little about the diseases that dinosaurs suffered from.
In the study of dinosaur lifespan, there are generally three models.
By analogy
Modern reptiles are one of the longest-lived animals on Earth, the giant tortoise
It can live for more than 150 years, and crocodiles and alligators can live for 60 to 70 years.
Birds, which are direct descendants of certain dinosaurs, also have long lifespans, swans and Turkish condors can live for more than 100 years, and some parrots tend to live longer than their human owners. Among mammals, elephants live for 70 years and chimpanzees for 40 years. Among fish and amphibians, the longest lifespan can live for 50 to 60 years. The only exception to the longest-lived mammals is the Arctic right whale, which lives for more than two centuries
Of course, we can't jump to conclusions that since some of the dinosaurs' close relatives and descendants could live for a century, the dinosaurs themselves must have lived a long life. For example, one of the reasons why giant turtles live so long is that they are cold-blooded animals with extremely slow metabolism, but whether dinosaurs are also cold-blooded is a controversial question.
In general, small animals tend to have shorter lifespans (with a few exceptions, such as parrots), so it is fortunate that the dragons live to be 20 years old. Conversely, larger animals, such as Arctic right whales, tend to have longer lifespans. But it cannot be said that Liang Long's body is 10 times that of an elephant, then its life expectancy must also be 10 times that of an elephant.
Metabolic mode
As mentioned earlier, larger animals tend to live longer than smaller animals. Extrapolating from this, earthquake dragons should be able to live for hundreds of years (especially those with super-large dinosaurs,
They come from almost no threat from predators, only disease, hunger, accidents, and old age.) However, if sauropod dinosaurs had the metabolic mechanisms of cold-blooded animals such as today's giant turtles, it is not unreasonable to infer their lifespan in a metabolic way.
How did dinosaurs metabolize? This is a hotly contested issue. Recently, There is a more credible conclusion that the huge herbivorous dinosaurs can achieve "constant temperature" because their bodies are extremely large, like a large house, which can be slowly warmed up and cooled down, so the internal temperature can be kept almost constant. Cold-blooded animals can also achieve constant temperature because of their metabolic methods, and if the confused dragon is completely warm-blooded, it will be roasted from the inside like a giant potato. In this way, it seems possible that dinosaurs had a lifespan of 300 years.
So how long did smaller dinosaurs live? The problem is complex, and even smaller warm-blooded animals such as parrots may have a longer lifespan. Most experts believe that the lifespan of smaller herbivorous and carnivorous dinosaurs is proportional to their size, for example, a chicken-sized megalosaur could live 5 to 10 years, while a much larger Allosaurus could live 50 to 60 years.
Bone growth patterns
You might think that an analysis of dinosaur skeleton fossils can help us understand how quickly dinosaurs grew and how long dinosaurs lived. Unfortunately, this is not the case. Biologists explain that the growth of bones is either continuous, such as mammals and birds, and some are cyclical, while the bones of different parts of dinosaurs show different growth patterns.
Some dinosaurs such as the Aguanosaurus with a duck's beak,
Its growth rate is extremely amazing, and it only takes more than a decade to grow into an adult dinosaur. The problem is that this rate of growth is clearly not in line with the metabolic patterns of cold-blooded animals, which means that some giant leather-eating dinosaurs, especially Crownosaurus, may have had the metabolic patterns of warm-blooded animals, and their maximum lifespan may be much lower than the 300+ years described earlier.
Some dinosaurs grow similarly to crocodiles, growing slowly and steadily. The emperor crocodile is a "super crocodile" that lived in ancient times, and it takes about 35 to 40 years to reach the size of an adult crocodile, and then maintains a slow growth rate throughout its lifetime. If sauropods had grown in the same way, their metabolic patterns would have been the same as those of cold-blooded animals, and their lifespan would have exceeded 300 years.
What kind of conclusions can we draw about the lifespan of dinosaurs? Unless we know more about how dinosaurs metabolized and grew, any conclusion would be a guess.
How high is the IQ of dinosaurs?
An stegosaurus stood on the podium and addressed its fellow dinosaurs: "The outlook is rather bleak, gentlemen, the global situation is changing, mammals are taking over the world, and our brains are only the size of walnuts." ”
For more than a century, this passage has been commonly used to summarize the intelligence of dinosaurs. The first fossil dinosaur (stegosaurus) excavated in 1877 showed that the dinosaur's brain was very small, like a walnut. We might think that if dinosaurs had a higher IQ, maybe some of their members would have survived somehow!
Dinosaur Intelligence Judgment Method: "Brain Formation Quotient"
Since we have no way to go back in time to iq testing dinosaurs, scientists have used a parameter called the brain-forming quotient to assess the intelligence of animals, which is to measure the ratio of the animal's brain to the rest of the body, and then compare it with other species of similar size.
One of the reasons why human beings can become the spirits of all things is that human beings have developed brains.
The "brain formation quotient" of humans is 5 (some people are as high as 8). That doesn't sound like a big number, but let's take a look at the "brain formation quotient" of other animals: 0.68 for antelopes, 0.63 for African elephants, and 0.39 for possums. As you can imagine, monkeys have a higher "brain formation quotient", with 1.5 for red colobus monkeys and 2.5 for monk monkeys. Dolphins are the closest animals in the world to the "brain formation quotient" to humans, and bottlenose dolphins have a "brain formation quotient" of up to 3.6.
It is conceivable that the "brain formation quotient" of giant dinosaurs whose brains are only the size of walnuts is very low. According to the analysis of dinosaur fossils, the "brain formation quotient" of triangular dinosaurs is about 0.11, but if compared with the slow-moving behemoth Brachiosaurus, the triangular dinosaur may be regarded as a "first-class genius", and the "brain formation quotient" of brachiosaurus is not even 0.1. However, some agile bipedal dinosaurs had relatively high "brain formation quotients", and although their intelligence was not as good as that of modern antelopes, at least their movements were not too clumsy.
Were carnivorous dinosaurs smarter than herbivorous dinosaurs?
One of the confusing questions about animal intelligence is that, under normal circumstances, an animal's survival requires having intelligence sufficient to adapt to its surroundings and survive in such an environment. Because the bodies of herbivorous sauropods were so large, carnivorous dinosaurs that preyed sauropods had to be slightly smarter than they were, and the relatively large brains of these carnivorous dinosaurs were attributed to the need for sharper vision and better muscle coordination. According to this deduction, the reason sauropods are more clumsy is that they only need to be a little smarter than plants!
However, we may have exaggerated the intelligence of carnivorous dinosaurs. For example, the scene in the film Jurassic Park about the collective hunting of dragons is just science fiction. If you encounter a living Thornosaurus on Earth today, you'll find it a little dumber than a modern bird of the same size, and you certainly can't teach it anything, because its "brain form quotient" is not at all on the same level as a dog or a cat.
Did dinosaur intelligence evolve?
From our perspective today, the intelligence of the dinosaurs who lived hundreds of millions of years ago is not worth mentioning. But we should remember that the intelligence of primitive humans five or six million years ago was also incomparable with that of modern humans, although they were a little more intelligent than other animals of their time.
This raises the question: What if some species of dinosaur had survived a mass extinction event 65 million years ago? A hypothesis by a famous Ji biologist once caused a sensation. He hypothesized that a wounded-toothed dragon of similar size to a human with similar intelligence to a possum rat might eventually evolve into a brain comparable to that of humans if it had the opportunity to go through another multi-million-year evolutionary process.
Of course, this is just an interesting guess. The size of the brain also depends on how it is metabolized. If dinosaurs were indeed cold-blooded, there is no doubt that they would have to evolve into the metabolic patterns of warm-blooded animals before they had the opportunity to further develop their intelligence; even if they were already warm-blooded animals, their lower "brain formation quotient" meant for them that it was a long way to go to catch up with them at the level of intelligence.