Why were all animals before humans so big?

It's very simple, let's talk about the food chain first, and you'll understand. Carnivores-herbivores-plants.

The reason lies in the plants at the bottom of the food chain. Because the plants used to be taller. So herbivores have to be tall enough to eat plants if they want to eat them. Carnivores can't be smaller than herbivores if they want to eat herbivores. So they're all taller (like dinosaurs).

Actually, there are a lot of small animals, too. The little dinosaurs ate insects. In general, the animals of the past were much larger than the current ones (such as dragonflies), mainly depending on the size of the food. Animals evolved based on food.

The first floor said that the plants used to be relatively tall? This is nonsense!

Prehistoric ferns, no taller than today's plants.

There is a theory as to why prehistoric animals were so large because of the relatively high concentration of oxygen in the air at that time.

Small refining is a direction of evolution, and today's scientific and technological products are not all pursuing small.

Third Floor Wild Flying Sun Don't talk nonsense, how do you know that the plants were not high in prehistory??? Please check the information. Today's syncope plants are not high, because the environment has changed, and prehistoric syncope plants are also very high, so learn a little more about it, and according to you, the concentration of oxygen in the air was relatively high at that time, so you can grow taller every day???

Can this theory stand on its feet? Don't take non-mainstream theories as an example.

Just according to what you say, the higher the oxygen concentration, the taller the animal. Plants that live in the same concentration environment at the same time. Isn't it supposed to be tall too?

Didn't you shoot yourself in the foot? Use your brain before you speak. The landlord asked why the animals were tall before.

It mainly depends on the conditions of survival. That is, food. It's better than eating food and you're going to die, right?

If you want to survive, you have to evolve. in order to adapt to the living conditions. This is also an evolutionary necessity.

You want to grow as tall as Yao Ming. I hang an oxygen cylinder every day).

The environment in which prehistoric giant organisms are located has a high concentration of oxygen, and the genes of the organisms and the conditions at that time are conducive to the growth of prehistoric organisms, and now animals are generally smaller because of the low oxygen content and the survival of large prehistoric organisms.

You will find that they are very large when you are in the ** prehistoric creatures, take dinosaurs as an example, dinosaurs are cold-blooded animals, and the size of cold-blooded is directly proportional to the temperature at that time.

In prehistoric times, scientists found that the atmosphere at that time was not as thick as it is now, and the sun was stronger than the energy that irradiated the earth now, the temperature was relatively high and the oxygen content was also high, which was conducive to the growth needs of large organisms, and if the dinosaurs were pulled to today's environment, it was estimated that they would suffocate to death because of the low oxygen content.

The genes of prehistoric creatures dinosaurs are not as complete as they are now, the animals in the age of dinosaurs lack reproductive genes that inhibit the growth of cells, just like the current crocodiles and dinosaurs belong to the same era, as long as the crocodile does not die, the body cells have been growing, but because of various factors such as temperature, oxygen content, etc., the crocodile is not as big as prehistoric.

The reason for the huge size of prehistoric organisms was determined by the climate and atmospheric oxygen content at that time, as well as the indispensable reasons for adapting to the environment, sufficient food, sufficient space, and good natural environment.

1. High oxygen content in the air.

Explaining this strange phenomenon in prehistory, scientists point out that the appearance of giant organisms hundreds of millions of years ago was related to the high content of oxygen in the atmosphere, which once reached 35%, far exceeding the oxygen content in the air today (the current oxygen content in the Earth's atmosphere is 21%), so the individual animals were larger than they are now.

2. The natural environment is excellent.

At that time, the climate of the earth was warm and humid, and the forest was full of dense forests, and the forests were inhabited by a variety of animals, so both plants and animals-eating dinosaurs had endless delicacies. Because of such a good environment, the prehistoric giant insects were hundreds of times larger than modern beetles, butterflies and cockroaches.

3. The temperature is low and the climate is suitable.

The comprehensive results of modern archaeology show that most of the animals that were tragically extinct in prehistory died around 10,000 years ago, and there must have been a sudden change in the earth's climate during this period, so it indirectly led to the large size of the animals at that time. Prehistoric temperatures were lower than they are now, and lower temperatures required larger individuals for animals to preserve their body temperature.

4. Survival of the fittest. Organisms with strong adaptability are preserved in the competition for survival, and those with poor adaptability are eliminated. This is a fundamental thesis of Darwin's theory of evolution. Moreover, at that time, the strength was determined by body size, and large animals had an absolute advantage in survival.

In the late Paleozoic Era, more than 300 million years ago, dinosaurs once ruled the earth with some other giant insects. Explaining this strange prehistoric phenomenon, scientists point out that the appearance of giant organisms hundreds of millions of years ago is related to excessive levels of oxygen in the atmosphere. If oxygen levels rise again, there is a good chance that Earth will once again become a paradise for giant monsters.

Scientists at the university noted that prehistoric giant insects were hundreds of times larger than modern beetles, butterflies and cockroaches. According to Professor Alexander Kaiser, who led the research, the size of the prehistoric giant insect is directly related to the amount of oxygen in the atmosphere. According to the analysis, the oxygen content in the Earth's atmosphere once reached 35%, which is 14% higher than it is now (the current oxygen content in the Earth's atmosphere is 21%).

It is reported that in the course of the study, scientists also specifically analyzed the relationship between the body size of modern insects and the length of their trachea. For example, in those days, a dragonfly could reach 70 centimeters on its wings. Scientists explain that more than 300 million years ago, the ratio of insect body size to the size of their trachea reached a very high level – because the higher the concentration of oxygen in the atmosphere, the less capacity the respiratory system has to process the air.

With the current relatively low oxygen concentration, the theoretical size of the insect does not exceed a few centimeters. However, once the level of oxygen in the atmosphere increases to the level of the Paleozoic, then the mosquitoes and cockroaches that we usually see may pose a great threat to human life. Adopt it.

As with many other animal groups, there has been a tendency to increase the number of individuals during evolution. But after the individual enlarges, the body returns.

physical support, exercise, and physical activities all have an impact, thus limiting the maximum length and weight of the individual. Dinosaurs far surpassed previous invertebrates and vertebrates in length and weight, and only the blue whales that now live in the ocean can compare in length and weight to dinosaurs. The largest contemporary land mammal is the African elephant, which is about 11 meters long and weighs 12 tons, but it is also much smaller than some dinosaurs.

Experts believe that the fact that dinosaurs could be so huge is inseparable from the relatively warm and humid climate and abundant food at that time.