The most direct and reliable evidence is a large number of fossils excavated in paleontological research. Fossils are the general names of the remains and relics of ancient creatures preserved in strata and the remains and relics of biological activities. Different fossils found in different geological ages are real records of the occurrence and development of various organisms in different periods of earth evolution. Therefore, fossils are one of the most convincing historical evidences that can prove biological evolution.
Through fossils, people know that there was no life on the earth in the early days of Archean. The earliest known traces of life appeared 3.4 billion years ago. Some primitive animals and plants began to appear in Proterozoic, mainly unicellular green algae, protozoa and coelenterates. Paleozoic fossils are so rich that almost all invertebrates can find their representatives. There is an ancient creature belonging to the phylum Arthropoda called trilobite. Its shell can be easily preserved as a fossil. It can be clearly seen from the fossils that this small animal appeared in the early Cambrian, reached its peak in the late Cambrian, gradually declined after Silurian, and was not completely extinct in Permian. It lasted for hundreds of millions of years and there were as many as 10 thousand species, so some people called that era "trilobite era"
The Middle Paleozoic was the heyday of fish. At the end of Paleozoic, amphibians developed highly, and primitive reptiles and primitive gymnosperms appeared at the same time. Mesozoic is the era of reptiles and gymnosperms. In the middle of this generation, dinosaurs dominated the world and were widely distributed in land, water and air. Modern creatures appeared in the Cenozoic era, and large reptiles and gymnosperms such as dinosaurs were basically extinct, replaced by birds, mammals and angiosperms. In the late Cenozoic, 2 million to 3 million years ago, biological evolution reached its peak and completed the transformation from apes to humans.
The discovery and study of fossils clearly show that all kinds of life on the earth do not appear at the same time, but early and late. The earlier the strata are excavated, the simpler the fossil structure is. The more complex the fossil structure excavated in the later strata, the more similar it is to the present biological types. The general trend of evolution is from simple to complex, from low to high, and from few to many types. This clearly shows that life is constantly advancing in the long historical development, and all kinds of creatures are formed through the gradual evolution and development of hundreds of millions of years.
Some transitional fossils, such as archaeopteryx fossils, have the characteristics of birds and reptiles, indicating that birds evolved from ancient reptiles. There are hundreds of fossils of various horses. If arranged in geological chronological order, we can clearly see the whole change process from ancestor horse, gradually new horse, Sino-Singapore horse, Shangxin horse to modern horse.
In addition, some organs are very developed and useful in some organisms, but they are obviously degraded and useless in others. This is called a "trace organ", like a human appendix. The history of species evolution can be traced back to the existence of trace organs. There are traces of hind limb bones in the whale, indicating that the whale originated from terrestrial vertebrates. Python is naked and has no legs, but there are traces of limbs in its body, indicating that it originated from quadrupeds.
It is convincing to study the process of biological evolution by excavating fossils, but it is not an easy task. Any conclusion can only be reached after hard excavation and serious textual research. Since scientists in China discovered the fossils of "Sinosauropteryx" and "Confucius Bird" in recent years, a debate about "who is the true ancestor of birds" has started. However, many Chinese and foreign scientists, after looking at the fossils of the Chinese dragon bird, think that this is a dinosaur fossil rather than a bird fossil. Although both Confucius and Archaeopteryx lived in the late Jurassic of Mesozoic, the geological age of the stratum where Confucius fossils were located was a little later than that of Archaeopteryx. So the earliest transitional bird fossil found in the world is the archaeopteryx of Germany. But the debate continues.
Comparative anatomy also provides strong evidence for biological evolution. In many different kinds of organisms, some organs with similar positions have great differences in appearance and function, but their internal structures are basically the same, and they have similar origins during embryonic development. Such organs are called "homologous organs". For example, the wings of birds and the forelimbs of mammals. This shows that they all originated from primitive reptiles. On the contrary, some organs are similar in appearance and function, but their internal structures and origins are different in embryonic development. Such organs are called "organs with the same function". Such as the wings of birds and flies. This shows that these creatures did not develop from the same ancestor, and their organs tend to be consistent in the process of adapting to the development and changes of the external environment, forming similar forms.
Embryological evidence is more interesting. The embryonic development of all higher animals and plants starts from a fertilized egg, which seems to indicate that higher organisms originated from lower single-celled organisms. Fish, amphibians, reptiles, birds, mammals and humans are very different in mature individual morphology. But observing their early embryos, they are too similar to be recognized. In early embryos, all kinds of higher organisms have branchial fissures and tails, big heads and bent bodies, and only after a certain degree of development do they show different shapes. This shows that vertebrates have a common ancestor, and humans evolved from animals with tails. This phenomenon is the proof of Huxley and haeckel's "law of biological occurrence" in 1866, which is also called "recursive law". This is because organisms quickly reproduce the main evolutionary stages of their ancestors in individual development, which is a powerful and interesting evidence of biological evolution.
In addition, cytology, biochemistry and molecular biology can also provide evidence for evolution. For example, we can study the genetic relationship between species from the number and morphology of biological chromosomes. The same number of chromosomes and similar morphology indicate that they are closely related in species. If we use the method of serum comparison for identification, we will find that the genetic relationship between dogs and wolves is relatively close, but it is far from foxes and cows. Advanced science and technology provide a variety of sophisticated testing methods, which opens the door to the study of species relationship and biological evolution.
The geographical distribution of species also confirms the process of evolution from a certain aspect. For example, in Australia and New Zealand, there are many marsupials such as kangaroos and marsupials, as well as monophyletic animals such as platypus and echidna, but it is difficult to see placental animals. This shows that placental mammals first appeared in the northern continent, and then gradually migrated to the south. New Zealand's land left the mainland in the Mesozoic Jurassic, and Australia's land was separated from the northern mainland before the Mesozoic Cretaceous, so the new species in the northern mainland could not enter the area far from the ocean, which made the isolated land still maintain the level of the original mammalian species.
In a word, countless evidences give a good explanation to the scientific theory of biological evolution. With the support of convincing scientific theory and strong evidence, biological evolution theory and cell theory have become the basic theories of modern biological science, and led and promoted the vigorous development of various branches of biology.