Mammals rose from the ruins and conquered the world.
About 65 million years ago, when huge meteorites hit the earth and cleared dinosaurs, the earth was in chaos. For surviving creatures, the race to become the new ruler of the earth has begun, and recent research shows that our ancestors were the first to act.
Meteorite impacts the earth
when the weight of the 34 billion tons meteorite impacts shallow near Mexico now at 30 km / sec, which changed the history of the earth. The energy released by the impact is equivalent to 1 billion tons of nuclear bombs. The burning rocks fall through the atmosphere to the surface, causing wildfires and tsunamis throughout the earth. For decades, dust clouds throughout the earth have blocked the sun, temperatures have plummeted, and plants have died. After 160 million years of rule over the Earth, large dinosaurs died with 75% of the animals on Earth.
In the ruins of the lost world, a small group of survivors, including birds, crocodiles, snakes and mammals, still exist. The planet is waiting to be conquered, and the cruel race begins to approach the top of the food chain and become the new ruler of the planet. Today, 65 million years later, scientists finally have a clear understanding of the period of intense competition.
The meteorite impact marks the end of the Cretaceous and the beginning of the new era, the Paleogene. After the darkness and cold, the dust settles, the greenhouse gases slowly release from the interior of the earth, and the earth warms again. At that time, the temperature was nearly 15 degrees higher than the current average temperature, and the warm climate extended to the poles. The lush tropical rainforest and broad-leaved forest cover most of the land, with no ice on either pole. In many ways, the Earth has returned to its heyday. Large herbivorous dinosaurs and excellent predators once ruled the planet, and now they have basically disappeared, except for a group of dinosaurs, birds, which survived. Other populations have also been greatly affected, with only 10% of mammals surviving.
Evolution to win the war
In order to win this war and become the ruler of the earth, these animals have evolved. Birds are getting bigger and bigger, giant birds have strong legs and powerful jaws, and some birds may be at the top of the food chain. Their scaled relatives – crocodiles also want to be the rulers of the earth. During the evolutionary process, some crocodiles became very large, and some crocodiles became fast-running land predators. The snake also joined the battle and evolved a 14-meter-long Titan. In order to take over the throne left by large dinosaurs, each group of animals developed explosively. However, they were all defeated by a group of small insectivores (mammal ancestors) like mice, which quickly developed different life forms that ruled the world today.
For many years, the early evolutionary bio-evolutionary competition has been a controversial subject in academia. Geneticists calculate the evolution of individual animal populations by analyzing the genes of modern organisms. Geneticists compare the genetic differences between dogs and elephants, and when the rate of difference is known, they can tell when the common ancestors of the two species lived. According to the equilibrium evolution rate, this research method shows that the ancestors of modern mammals originated from the Cretaceous (150 million years ago – 65 million years ago). While the dinosaurs flourished, they have lived on Earth for thousands of years, but their evolution did not begin until the death of large dinosaurs.
The accuracy of this method is not high, especially when the time required for calculation is long. Therefore, some scientists use fossil methods, and the bones in fossils tell a completely different story. In the fossil study of the most detailed meteorite impacts to date, scientists at University College London provided us with a clear process of early mammalian evolution. Scientists have studied several different aspects of early mammalian evolution. First, they observed the number of species and found that a large number of new mammalian species evolved in the early Paleogene; subsequently, they analyzed changes in shape and size between species and found that mammals evolved in a very short time. A variety of body types have emerged. The results show that at the moment when large dinosaurs disappeared from the surface, mammals did not hesitate to begin an “explosive” evolution.
What is a mammal?
We have some very basic consensus on mammals. For example, we can live with milk only when we are young. For example, we have hair, a warm-blooded animal, and we are a placental mammal, and we give birth to the offspring in the womb. However, in addition to the above basic common sense, how are mammals defined and how they evolved? Why are humans more similar to foxes, hedgehogs, and giraffes, unlike pythons, tortoises, or penguins?
To answer these questions, biologist Liam Dulu believes that we may be able to use methods that were once popular in the 18th century. The definition of animals and plants at that time was determined by their common characteristics. Based on similar principles of reproductive biology and breathing, Carl Linnaeus announced in 1758 that whales and dolphins were not fish, but were members of the thermostatic terrestrial bioline. In order to name this new group, Linnaeus chose the feature of the breast to classify these creatures as mammals. A century after Linnaeus completed the classification of mammals, Charles Darwin published his greatest book, The Origin of Species, in which the concepts of natural selection and evolution were widely accepted by biologists.
Darwin believes that mammals have many similar characteristics, probably because they all share a common ancestor. To explain where these features come from, first we need to figure out the advantages of these features, and where do the features that these ancestors did not have come from? For example, how does the mammary gland “have nothing”? The closest species to mammals are reptiles. Currently, we know that the lineages of mammals and reptiles have evolved in different directions about 310 million years ago, and their last common ancestor looks more like reptiles. Non-mammal. This common ancestor, beginning with cold blood, less milk, and hairless, has evolved into a true mammal, which has evolved the characteristics of today’s typical mammals.
The first species considered to be mammals appeared 210 million years ago. Most of the mammalian evolutionary information we know is obtained from fossil records. Now scientists compare the body and DNA of 5,500 mammals, and the research results extracted from it are combined with fossil records for deeper Species research.
Seven characteristics of success
Several distinct features of mammals help them have a good start in the competition. Even today, these features help mammals maintain their dominance.
One of the most unique features of mammals is the ability to produce milk. White liquids originate from mammalian ancestors resembling reptiles, which in a dry environment keep the eggs moist with a white liquid. When they start to let the eggs develop in the womb and give birth to their offspring, the milk gains another function—providing them with the best nutrition in the early life of the offspring, and the milk can also allow the mother to transfer the immune body, so Prevent future generations from getting sick. Parents no longer need to find food for future generations, they no longer rely entirely on food.
Fur is also very important for early mammals. It helps mammals stay warm when temperatures drop, and when they are hot, they can block heat. Body temperature is determined by rapid metabolism, and metabolism ensures constant body temperature. Constant temperature provides optimal conditions for somatic cells, allowing animals to maintain high energy throughout the day. Unlike cold-blooded reptiles that rely on sunlight, mammals can adapt to cold areas or be active at night. The extra energy allows mammals to forage in larger areas and prey on prey more efficiently.
Mammals have evolved more complex hearts, making high activity levels possible. The reptile’s heart has only three ventricles, and the mammal has developed a heart with four ventricles. An extra ventricle means that oxygen-rich blood from the lungs is not mixed with oxygen-poor blood from the body before being pumped into the blood vessels. Therefore, somatic cells can continuously receive a large amount of oxygen, keeping the animal’s rapid metabolism and keeping the animal active.
Teeth are another major advantage of mammals in race competition. Unlike most other animal populations, each mammal has many different types of teeth in its mouth, and the type of teeth varies from species to species. Humans have anterior teeth, canines and caries, and each type of tooth has its own function. Like other mammals, teeth allow us to eat a variety of foods and smash them, so we can absorb nutrients faster and more efficiently.
The flexible limbs of mammals enhance mammals’ ability to adapt to different habitats and foods. When the bird’s hand is reduced to a set of feathered fingers, the mammal can flexibly use the limbs, crawling, digging, handling food and tools, and supporting their heavy body. The limbs can be freely used to allow mammals to better utilize the surrounding environment and resources to promote the growth of mammals.
However, the key to mammals’ ability to conquer the earth is their head. The first mammals evolved a new set of bones in their ears called the humerus and the anvil. New bones, along with the tibia, also found in reptiles and birds, allow mammals to hear higher frequencies that other animals cannot hear. In addition, ancient fossils show an improvement in the mammal’s sense of smell and sensation. Adequate research on mammalian ancestral skulls has revealed an improvement in sensory effects.
The brain is a very large organ in a mammal, covered by special brain tissue. Because neural computing requires a lot of energy, mammalian brains are closely related to body temperature. Some people even think that high intelligence is an important driving force for animals to evolve a constant temperature.
In order to deal with sensory impressions, mammals have evolved larger brains and soon used new parts of the brain. The function of the new brain center gradually changed from explaining the sensory impression to solving the problem. Most of the human cerebral cortex develops from these new features. Intelligence is one of the most important factors when animals need to adapt to a new living environment. Ancient mammals are smart enough to conquer the entire planet.
Cold means new opportunities
when mammals became the dominant species, they will never give up this position. After 20 million years of meteorite impact, climate change has brought more benefits to mammals. The continental drift caused Antarctica to separate from Australia, and new ocean currents around Antarctica stimulated the slow cooling of the Earth. As the temperature dropped, the ice caps of the two poles began to grow, and the water was “bundled” on the ice, causing the water level to drop and a new continental bridge between the separated areas. In addition, India and Asia collide, Africa collides with Asia, and Europe and North America are in contact with South America, making mammals easier to spread. The cold climate has also changed the composition of the ecosystem. The earth is no longer just a forest. It includes deserts, tundra and vast grasslands. The new environment paves the way for more variation in mammals and promotes large herbivores. The development of animals and predators.
Mammals have won both the ocean and the land, but the key to success is not the number of species. In fact, the number of species of birds and reptiles exceeds that of mammals. Mammals are able to become dominant species because of their unique and diverse body shape, lifestyle, habitat and size. Mammals have wings, fins and legs that live in mountains and underground, including the smallest terrestrial vertebrates and the world’s largest animal, the whale.
The meteorite impact changed the fate of the earth in a matter of seconds, leaving a variety of possibilities. If the meteorite does not hit the earth, or if the mammal’s evolution is very slow, the world may be completely different. But the combination of these random factors made our ancestors a winner.
Today, mammals live in a variety of different terrains in the world, ranging from arctic foxes and polar bears to scorpions and deer; from wildebeests and cheetahs to camels and desert pelicans. Whale swimming, horses running, bat flying, kangaroo jumping, monkey climbing, big world, no wonder. Mammals become species that rule the planet.