Nobel laureate Australian scientist John Echole mentions in his book The Evolution of the Brain that the brain evolved from fish brains to reptile brains, to mammalian brains, and finally to the human brain. If we analyze the human brain, we can clearly see that the structure of fish-like, reptile-like, and mammal-like is clearly distinguished in the human brain.
In fact, the evolution from fish to man is a comprehensive evolution, including human appearance, body shape, and even reproductive mode. But more importantly, there would be no human evolution without the evolution of reproductive methods.
< h1 class= "pgc-h-arrow-right" > shield fish invented sexual intercourse</h1>
Today, human reproduction must be combined with sperm and eggs, and the union of sperm and eggs must rely on the mating of reproductive organs of both sexes. Although sexuality has too many tasks and complex contents, such as the pleasures of sexual life, and strange sexual behavior, the inventor of sexual reproduction is the fish, to be precise, the small-limbed fish in the shield fish
Shieldfish are the most primitive jawed animals. The human face that develops into the upper and lower jaws is also derived from the shield fish (also known as the initial whole jaw fish).
That was 440 million to 360 million years ago. Nowadays, most of the facial bones known as "faces" can be found from the upper and lower jaws of fossils in ancient times. But later, pelagic organisms evolved a breeding behavior that humans follow today—sexual mating. About 380 million years ago, the small limb fish invented today's sexual behavior that is both happy and obsessive, as well as red-faced.
John Lang, a professor of paleontology at Flinders University in Australia, confirmed the finding in an article published in the British journal Nature. They have conducted long-term studies of small-limbed fish living in Scotland, Estonia and China. Previously, they had been unable to understand the function of certain organs in the fish, which was about 8 centimeters long.
When they studied the appearance of these fossils, they found some of them with a pair of strange lateral branches at the end of the shell of the abdomen body. This lateral branch structure is very similar to the previously discovered finned foot, but it is not a traditional fin. In general, fish can be divided into dorsal fin, fin, caudal fin, pectoral fin and ventral fin according to the position of the fin. They have a variety of functions to promote, balance and guide fish activity.
The lateral finned feet of small-limbed fish differ, and now researchers understand that this flipper is the intersection of the abdominal fins of male cartilaginous fish that mutates to adapt to in vivo fertilization. John Lang et al. believe that the lateral fins are the skeleton part of the male external genitalia of the small-limbed fish, the male L-shaped fins are a "reproductive tool", and the fossils of the female small-limbed fish do not have such lateral branches, but have a pair of bone plates, equivalent to the female's "mating groove", which is used to support the reproductive organs of the male fish for mating.
However, the external genitalia of male small-limbed fish extend laterally, almost at a 90-degree angle to the body, and it seems difficult to mate with females. The researchers speculate that the small-limbed fish are identical to the male and female when mating, their joints and hard pectoral fins are held against each other, the male extends the "mating process" to the side of the female's body to the bottom, and the female is trapped by the female's "mating groove" to complete the mating behavior.
In this way, the male can enter the female's body and deliver sperm to the female in a targeted and quantitative manner. Today, it is said that sex is an innate human instinct. While this is not entirely true to sexologists and physiologists, some of them are true from the source of evolution. Because the earliest ancestors of human beings already made people have this instinct, otherwise, human beings would not have evolved to this day.
< h1 class= "pgc-h-arrow-right" > why do small-limbed fish reproduce in both sexes? </h1>
Why do small-limbed fish reproduce in this way that sexual organs mate? Researchers may not be able to explain the complexity and diversity of human sexuality today, but they can be explained by the efficiency of reproduction.
Therefore, it is necessary to distinguish between the three breeding methods of today's fish: oviparous, oviparous and viviparous
Oviparous means that the female lays eggs directly in the water, the male follows, and the sperm is released onto the egg for fertilization, and the fertilized eggs develop in the water to hatch the juveniles. This method is mainly used for the reproduction and reproduction of fish. Females lay their eggs directly in the environment, unprotected, and can be swallowed by other aquatic organisms. Second, the male releases sperm after the female spawns and fertilizes the eggs, which is similar to the thin harvest of a wide species. It is not very targeted, like shooting birds with shrapnel, very effective, but not efficient.
In this way, the female produces a large number of eggs. For example, carp and crucian carp produce hundreds of thousands of eggs a year, while sunfish can lay up to 300 million eggs. As a result, ovate fish have a low fertilization rate but a large spawning volume.
Viviparous is when a fish's eggs are fertilized inside a female. The fertilized egg develops in the reproductive tract and has little nutritional connection with the mother. During development, the nutrients required by the embryo are provided entirely by the egg itself, and as such, it is a form of in vivo fertilization and incomplete growth in the body. Peacock fish, swordtail fish, crucian carp and some sharks are all oviparous. Females gradually enlarge their abdomen after estrus, with black fetal spots. At this point, the male will continue to chase the female, and then insert the hybrid agent into the cloaca of the female to expel sperm and undergo internal fertilization.
Obviously, oviparous birth is more efficient, safer, and more advanced than oviparous birth. Fertilization and survival rates are higher. It is also inherited from small-limbed fish.
Viviparous is when male fish fertilize female fish in the body, and the fertilized egg also matures in the body. The embryonic body formed by the fertilized egg has a blood circulation relationship with the mother. Its nutrition comes not only from the yolk, but also from the mother's supply. It is a form of reproduction in vivo fertilization and growth in vivo. Only a few fish, such as the grey star shark and the true shark, are viviparous. During the breeding season, the male discharges sperm through a mating apparatus to the female's vent hole, and then the sperm and egg combine inside the female's body, and the fertilized egg forms an embryo. The developing embryo and the mother obtain nutrients through blood circulation, and the place where the mother gives birth to the small fish has also changed, forming a placental-like structure similar to that of mammals, but there are still great differences, so it is called pseudo-fetal birth to show the difference from the real fetal birth of mammals.
This condition is similar to the birth of mammals and humans, apparently inherited from small limb fish. Because the offspring of fetal raw fish are highly protected, only a few are produced in this way, generally only a few, and no more than 10 at most, but they are highly efficient and energy-efficient.
The so-called high efficiency is, of course, calculated from the ratio of efforts to the benefits of population reproduction. Fish spawning requires a wide variety of fish, so pay more and harvest less because the offspring cannot be protected. Viviparation not only protects offspring, but also has a high survival rate, and the cost and effort paid by parents is also very low.
< h1 class= "pgc-h-arrow-right" > more bizarre fish mating</h1>
However, why do only a few fish inherit hermaphroditism in vivo, while most fish have not yet evolved this mode of reproduction, and why do humans inherit the method of intercourse and reproduction from small limb fish?
Although these two questions are not easy to answer, they also have evolutionary inevitability and chance. All of the above illustrates the inevitability and safety of mating. As far as chance is concerned, another fact of evolution can be partially explained. Although bonobos are sexually similar to humans, only Australopithecus Africans evolved into humans, while other primates, such as monkeys, chimpanzees, and bonobos, did not evolve into humans, and today they cannot evolve into humans. This is the opportunity.
The sexual behavior peculiar to other fish may also explain why small-limbed fish use sexual intercourse to reproduce their offspring.
A study published in the journal Animal Taxonomy shows that there is a very strange fish in the Mekong Basin of Vietnam, the throated fish, whose genitals are on the head. This small fish is one of 22 species and genera of known spermatomycenes. The reproductive system of this fish grows on the mouth. As a result, their mating becomes a strange phenomenon. The male of the laryngeal fish places the genitals into the opening of the reproductive system next to the female's mouth to complete the fertilization.
Located in Washington, D.C., Linni Parenti, curator of the National Museum of Natural History, explains that this peculiar mating process is a feature of spermidal fish. In general, the mating process of fish is usually short, almost instantaneous. However, this is not the case with spermidal fish, whose reproductive organs remain together for long periods of time. It seems a bit like mating between humans and mammals today, pursuing longer mating times to enjoy "sexual bliss".
Of course, according to the researchers, the evolution of the genitals of the spermatomot family on the head is not because of "sexual happiness", but similar to the genital evolution of small limb fish, and many of them have similarities. The ancestors of this fish allowed males to fertilize females in their bodies, just like small-limbed fish, and later they evolved the strange shape of the genitalia of the head, just like the males of small-limbed fish have L-shaped concatenations.
A more plausible explanation, however, is that head-to-head mating is a more efficient form of mating, ensuring that all the eggs are fertilized as much as possible.
Like other sperm fish, the body length of this fish is usually about 2.5 cm, and the body is almost transparent. This new species was first discovered in shallow waters of the Mekong River Basin in Vietnam, an environment in which spermidal fishes usually live. This fish also has a strong adaptability, and they are gradually adapting to the modern ecological environment. Now, researchers have found their tracks in some highway culverts.