Reproduction is one of the most important issues in animal life. In order to stand out in the fierce breeding competition and seize the opportunity, the male animals showed their magic and evolved Tintin of different sizes and shapes.
Although human beings are advanced intelligent beings, they cannot escape the laws of evolution. Studies have shown that women have hidden ovulation periods in their evolution, all year round, with unlimited numbers and times; Males have also lost important traits in evolution, and genetic studies have found that the tintins of human ancestors had bones (penile bones), which is far from modern humans.
Human Tintin once had bones, but why were they lost in evolution?
Tintin's long bones sound bizarre, but it is actually a universal natural phenomenon. Among human close relatives, there are still primates who retain this bone, such as gorillas and chimpanzees, which have a penis bone.
Chimpanzees also have tintin bones
Biological anatomy reveals the mystery of tintin bone, which is mostly stick-like in appearance, and the thickness, curvature, and size vary from species to species. For example, the gorilla's tintin bone is only 6mm, and the relative size is insignificant; The butadiene bones of walruses are 50 to 60 cm long, accounting for 16 to 18% of the body length.
Studies have shown that tintin bones are found only in 7 species of the eutherapia suborder, namely African shrews, carnivorous, pterodactyls, primates, rodents, and Lauya carnivorous. But in 2014, Weimann and other scholars studied an American pika, and found a tiny penis bone on its tintin, which caused a sensation in the scientific community.
Butadiene bone of different sizes and sizes
This discovery means that the range of tintin bone is more common, because the American pika belongs to the order Rabbit in taxonomy. Not only that, but the animal's tintin bone is also "unstable" and may also be lost during evolution.
Different species of tintin bone, with different morphological characteristics
In the case of mammals, for example, their penile bones were lost ten times in evolution and acquired nine times. Tintin bone is not a homologous structure, and different species of tintin bone have evolved independently. Primate tintin bones are generally small, only 1 to 2 cm, while humans are more special, there is no tintin bone, which is actually the result of evolutionary loss.
Phylogenetic tree of primates
What is the role of tintin bone? Some people may take it for granted that with tintin bones, animals will have a longer time to mate. There is some truth to this statement. Scientists believe that tintin bone can prolong the mating time of animals, generally more than 3 minutes, and male animals use this to improve the chances of female conception, thereby preventing females from mating with other individuals.
Scientists have also found a relationship between mating time and tintin bone: the more persistent male animals, the larger the size of tintin, and such animals generally have tintin bone support. Of course, there are exceptions to everything, such as: the black stars only have a single mating time of 15 seconds, but they still have a penis bone, even if the size is only about 8mm.
Co-evolution of the presence of tintin bone and the duration of insertion
Some friends may ask: If tintin bones are so important in competing for mates and prolonging time, why do humans lose it? In this regard, scientists also gave an explanation: this is related to human reproductive strategies.
Compared to other animals, human males have little sexual competition, and females typically have sex with only one male at a time. Over time, human fertility strategies have changed, which may be the last straw that "crushes" tintin bones.
How hard do the animals fight for mating?
Breeding competition is widespread, and as a result, species undergo adaptive evolution, and this change is not only reflected in faster speeds and stronger bodies, but also in the different forms of tintin.
In 2012, the American listverse website published the case of "the world's top ten unexpected animal tintins", which was really eye-opening. In front of these animals, the size of humans is completely unworthy, and the barnacles that rank first are a typical example.
Barnacles have shellfish-like shells, but they are not shellfish, but crustaceans, and are more closely related to shrimp and crabs. Barnacles are a "wave first and then home" character, in the larval stage will go through the free stage of planktonic larvae, arthropods, and glandular larvae, and after completing the metamorphosis, they will live in a fixed life, attached to the reef and the surface of turtles and whales, and can no longer move at will.
In order to reproduce offspring, barnacles evolved into very long tintins, almost 8 times the length of the whole body! During the breeding season, barnacles stretch out extra-long tintin to find nearby companions and store sperm in neighbors' bodies. Interestingly, barnacles are hermaphrodites, which can either be fertilized by a peer, "fertilized," or both.
If you want to talk about size, there is no creature on Earth that is more powerful than a blue whale. The blue whale is the largest surviving mammal on Earth, with a body length of up to 33 meters and a weight of 180 tons, and the matching Tintin is also quite large. According to the data, an adult blue whale is 500 cm long (ordinary length is 240 to 300 cm), 30 cm long in diameter, and weighs 68 kg. Depending on the size of each testicle, the amount of sperm per blue whale is estimated to be around 35 pints, or about 17 liters!
In addition to the blue whale, the tintin of some small animals is also very distinctive. For example, the male bed bug's junction (tintin) is thin and long, and can directly penetrate the female's abdomen and inject sperm into it. These sperm spread through hemolymphs into the ovaries of the female, achieving binding to the eggs. This form of mating is straightforward and violent, and scientists call it "Traumatic insemination."
However, this mating strategy also has drawbacks. On the one hand, female worms have wounds due to attack by male worms and are more susceptible to bacterial infection, resulting in a decrease in survival rates; On the other hand, injected sperm will also trigger an immune response, which is also not conducive to the improvement of viability.
Cats have barbs on their genitals, and ducks evolve spiral-shaped tintins
For humans, sexual behavior is not only for the purpose of reproducing offspring, but more likely for the purpose of obtaining physiological pleasure, and a prickly tintin will obviously be unacceptable.
Curiously, felines generally have prickly tintin, which will undoubtedly make the mating process extremely painful. Therefore, the female cat often screams during mating, and when the mating is over, she will even turn around and attack the male cat.
What exactly does the barb of the male cat Tintin do? Scientists have come up with two explanations.
The first explanation: stimulation of ovulation. The mother cat does not ovulate before mating, and the role of the tintin is to stimulate the reproductive organs of the mother cat and facilitate ovulation and fertilization.
The second explanation: complete mating. Felines are born with the instinct to be alone and escape pain, and the barbs on the male cat Tintin can prevent the female cat from escaping during the mating process, that is, strengthening the control of the female cat's body to ensure the completion of the mating process.
It is worth mentioning that the barbs on the cat are not born, but only begin to develop at 3 months of age, fully developed at 6 months of age, and the whole process also needs testosterone stimulation. As long as it is neutered early and the effects of testosterone are avoided, the tintin of male cats will not develop barbs.
If cat genitals are incomprehensible, then Tintin of ducks is even more outrageous. The butadiene of ducks has a spiral-like structure, resembling a corkscrew; The size is also very large, up to 20cm in length, accounting for about half of the body length. According to Wikipedia, the Argentine blue-billed duck can grow to 42.5 cm, and the average body length of the species is only 36 to 46 cm!
In contrast to Tintin's appearance, the female duck's genitals are anti-spiral, which makes fertilization extremely difficult. Speaking of which, everyone may be confused: why is there such a structure? Scientists believe that the construction of the female duck's genitals is the result of a "sex race"! Because in the duck world, forced mating is very common, males are very grumpy, and even female ducks die.
At this point, the structure of the anti-spiral increases the difficulty of fertilization, helping to get rid of (eliminating) the sperm of a particular male duck, which is equivalent to increasing the sexual selection of the female duck. If the female duck wants to mate with a male, the muscles of the cloaca can be relaxed, making the male duck's tintin more accessible and the sperm and eggs more easily combined. Thus, the reproductive structure of the spiral and the reverse spiral is actually a contest between male and female ducks over reproductive choices.
Scientists have also found significant seasonal variations in the length of duck tintin, with summers generally longer in size and winters shortest. It can be seen that Tintin's changes are far more "flexible" than imagined, and it is not surprising that Tintin is diverse!
summary
The tintins of animals are strange and varied, and on the surface there is no order to follow, but in fact they are the result of mating competition and adaptive evolution. Animals are like this, so why shouldn't humans?