Atavisms and rudiments, examples of which will be discussed in our article, are irrefutable evidence of the evolutionary theory of the development of living organisms. What do these concepts mean and what is the significance of their discovery for modern science?
Evidence of evolution
Evolution is the irreversible process of development of all living things from simple to complex. This means that organisms have changed over time. Each subsequent generation had more progressive features of the structure, which led to their adaptation to new living conditions. And this means that organisms belonging to different systematic units must have similar features.
For example, the forelimbs of birds and pinnipeds of mammals consist of the same sections. These are the shoulder, forearm and hand. But since birds are adapted for flight, this limb turns into wings for them, and for aquatic inhabitants it changes into flippers. Such organs are called homologous.
Another proof of the theory of evolution are analogies. So, both insects and bats have wings. But in the first they are derivativesepithelial tissue, and in the latter they are a skin fold between the fore and hind limbs. These organs have different origins, but have common features of structure and functioning. This phenomenon arose due to the divergence of signs, or divergence.
Atavisms and rudiments, examples of which are studied by comparative anatomy, are also direct evidence of the interconnection of all living things.
What is a rudiment?
Some organs are said to be "rudimentary developed". This means that it is not enough for the full implementation of the intended functions. Indeed, rudiments are called organs that have lost their original meaning in the process of evolution. On the one hand, they are developed to a certain extent, and on the other hand, they are at the stage of extinction. Typical examples of rudiments are a change in the shape of the auricle and the degree of development of the muscles that surround it. Our ancestors needed to listen every minute to the approach of danger or long-awaited prey. Therefore, the shape of the shell was sharper, and the muscles ensured its movement. For a modern person, the ability to move his ears is unlikely to be useful in everyday life. Therefore, individuals with such skills can be found very rarely.
Examples of rudiments in humans and animals
Insufficiently developed organs inherent in ancestors are found in animals quite often. Examples of rudiments are the presence of a coccyx in a person, whichis a remnant of the caudal spine, as well as wisdom teeth, necessary for chewing rough and unprocessed food. At this stage, we practically do not use these parts of the body. The appendix is a vestige that humans supposedly inherited from herbivores. This part of the digestive system secretes enzymes and is involved in the processes of splitting, but compared to the ancestors, it is significantly shortened. For comparison: in humans, its average length is about 10 cm, and in a sheep or camel - a few meters.
The list of human rudiments continues with the third eyelid. In reptiles, this structure moisturizes and cleanses the outer shell of the eye. In humans, it is motionless, has a small size, and the above functions are performed by the upper eyelid. A scar on the upper palate of a person is also a vestige - these are the rudiments of the next row of teeth, in which a person does not need.
The rudiments of animals are the hind limbs of whales hidden inside the body, and the h alteres of dipterous insects, which are a modified pair of wings. But in snakes, the limbs are not developed at all, because due to the peculiarities of their musculoskeletal system, the need for them is completely absent.
Rudiments: photo of plants
Plants also have rudimentary organs. For example, wheatgrass weed has a well-developed rhizome, which is an underground shoot with elongated internodes. Small scales are clearly visible on it, which are rudimentary leaves. Because undergroundIf it cannot perform its main function - the implementation of photosynthesis, then there is no need for their development. A rudimentary pistil in the form of a tubercle in the staminate flower of cucumbers is also a rudiment.
What are atavisms?
Another proof of evolution are atavisms. We can say that this concept is the opposite of rudiments. Atavisms are the manifestation in individual individuals of signs characteristic of their distant ancestors. Their presence also indicates a certain degree of kinship in a number of generations. In the early stages of embryo development, there is both a tail and gill sacs. If embryogenesis occurs correctly, these structures stop their development. In case of violation of the development process, individuals with structural features unusual for them may appear. Therefore, the tailed boy and the amphibious man are not just a fantasy.
Human atavisms
In addition to the appearance of the tail, typical human atavisms are excessive body hair. Sometimes it significantly exceeds the norm. There are cases when hair covered the entire body of a person, except for the palms and soles of the feet. The appearance of additional mammary glands on the body is also considered an atavism, and this can occur in both women and men. This trait is inherited from mammals that have had many children. At the same time, there was a need to feed them all at the same time. A person does not have such a need.
The second row of teeth is also a feature inherent in our distant ancestors. For example, sharks haveseveral rows. This is necessary for predators to effectively capture and hold prey. There is an opinion that microcephaly can also be considered an atavism. This is a genetic disease that manifests itself in a decrease in the size of the brain and skull. At the same time, all other proportions of the body remain normal. This entails mental retardation.
Man shows some signs of animals in the form of reflexes. For example, hiccups are a typical feature of ancient amphibians. This reaction was necessary for them to pass water through the respiratory organs. And the grasping reflex, which is especially strongly developed in children, is a manifestation of that in mammals. They grabbed onto their parents' fur to keep from getting lost.
Atavisms of animals and plants
Examples of the manifestation of ancestral traits in animals are the appearance of hair or hind limbs in cetaceans. This is proof of the origin of these animals from extinct ungulate mammals. Atavisms are also the development of extra toes in modern horses, movable limbs in snakes, and legless lizards. In primroses, an increase in the number of stamens up to 10 is sometimes observed. This is how many ancestors of modern plants had. Although modern species have only 5 stamens.
Causes of evolutionary change
As you can see, rudiments and atavisms appear in many species of plants and animals. This indicates a certain degree of kinship between representatives of different systematic units within the same kingdom. evolutionary changealways occur in the direction of their complication, as a result of which living organisms have the opportunity to better adapt to certain living conditions.
Having considered examples of rudiments and atavisms, we were convinced of the generality of the system of the organic world and the viability of the theory of evolution.
