It is said among the people that mule cannot have children. Even if you are pregnant, mule must pay the price of your life .
Have you seen this kind of creature
It turns out that behind all this is the trouble caused by "horse and donkey". What is the specific situation? Let's take a look together.
The birth of mule
Mule is a breed produced after the hybridization of horses and donkeys. The offspring of male horses and female donkeys is called "donkey mule", and vice versa is " horse mule ".
Most of the common mules in our lives are horses and mules, because the genes of horses and mules inherit the strength of horses and donkeys, has the most practical value .
The mysterious gene chain
And the probability of a horse and mule being born is about 70%, and donkey and mule being only 30%, which greatly increases the number of horse and mule in human society.
But not all hybrid species are so lucky, mules are just an exception.
For example, animals in zoos that look like both tigers and lions are called lions and tigers or tigers and lions . Their lifespan is less than either lions or tigers, and most of them die in childhood.
lion tiger beast and tiger lion beast
relatively, because the species relationship between horses and donkeys is very close, and in terms of chromosome pairing, there are 64 horses, 62 donkeys, and mules and lucky enough to get 63 chromosomes.
Mules inherit most of the advantages of horses and donkeys, and have relatively long lifespans, and can generally be sold for about 30 years by humans.
In my country, mules have a long history of appearance, and mules have appeared as early as the Spring and Autumn Period and the Warring States Period.
小小有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有有�
In modern times, with the development of biology, people have gradually mastered the skills of cultivating species, and a large number of mules appear in people's lives.
People use mules to farm, which in turn promotes the development of society.
Strong mule
Data statistics, as of 1985, there were about 114 million mule in the world, a large part of which were breeds cultivated in China.
Sadly, all mules do not have the ability to reproduce and cannot reproduce naturally.
Reproductive ability of mule
Biologically, the number of chromosomes in horse sperm cells is 32, and the number of chromosomes in donkey egg cells is 31.
, but since the genes cannot be fully paired, the mule's gene has a strong randomness of .
For example, one pair has 15 chromosomes from horses, 17 chromosomes from donkeys, and the other pair has 17 chromosomes from horses, and 14 chromosomes from donkeys.
Donkey Horse and mule chromosome arrangement
and so on, there are about 4.29 billion species, of which only two situations can produce fertilized eggs.
That is, all the chromosomes in it come from horses or all the donkeys.
Mule is not completely infertile, it just says that its fertility probability is astonishingly low and almost negligible.
Theoretically speaking, if the descendants are really born, the cub will tend to be one of the horses or donkeys when they grow up, and basically have no characteristics of a mule.
This seems to have returned to the starting point.
1 plus 1 equals the new 1
Before, people found offspring of a gray-white mule in Morocco, and people found that its offspring was more like donkeys.
Scientists have discovered through genetic tracking that the baby's father is a black donkey.
This little guy was not born naturally, but the offspring of the mother mule through scientific means after discovering that the mule is pregnant.
pregnancy will die
Generally speaking, female mules have sexual functions and also provide uterine for the growth of offspring, but does not have pelvic bone that can be opened and closed.
Pelvic bone is an essential body structure for mammalian when reproduction and offspring. The greater the tension of the pelvic bone, the lower the probability of females being difficult to give birth.
This is because when mammals reproduce, they need to give birth to fetuses in the uterus. The higher the animal, the longer it will be.
Fertilized eggs divide and develop in the uterus
This also leads to a problem. The fetus is getting bigger and bigger in the uterus, which puts a serious burden on the mother. At this time, it is necessary to have sufficient toughness to support it to help the fetus and the pregnant mother through the crisis.
When giving birth to offspring, due to the narrow and long birth canal, a large opening and closing pelvis is needed to cooperate.
If the pelvic bone is accidentally broken during the process, the fetus and the mother can only choose one, either the fetus will be strangled by the narrow space, or the mother will be broken and killed.
Humans are a good example. In the early days, the cycle of human raising offspring was more than 15 months. At that time, the fetus was burdened with women, and it was very dangerous for women to give birth to offspring.
For the sake of human continuation, women have evolved the reproductive characteristics of 10 months of pregnancy (actually only between 8 months and 9 months), and optimized the pelvic structure of , which only reduced the chance of difficult childbirth .
Pelvic bone structure
If there is no help from humans, the mule will die if it is pregnant for about one month. This is why it is said that mule will die if it is pregnant.
The probability of pregnancy is extremely low, and the risk factor for giving birth is extremely high, which makes mules unable to have children naturally.
However, there is no shortage of lucky newborns in the world.
Dispersed mule
1924, a female mule and stallion in South Africa gave birth to a foal. If people had not seen it with their own eyes, it would be hard to believe that this was the offspring of the mule.
Because this foal has all the characteristics of a horse, it is no different from the offspring given birth between the horse and the horse.
Another 7 years later, the foal's estrus arrived, mated with the other mare, and successfully gave birth to a descendant of pure blood. At this point, all the genes related to the mule disappeared.
horse cub
On the contrary, if the offspring of the mule is a donkey cub, then in the third generation, the gene will also return to the donkey.
This also shows that although mule is a new breed after hybridization, it cannot be independently a species .
Coincidentally, the famous biologist Anderson published an experiment in a magazine, mating a female mule with a rare snow dragon stallion and giving birth to a pure bloody snow dragon stallion.
If the probability of giving birth to offspring is too low, perhaps this method can be used to prevent the blood of some species from being "contaminated".
xuelongma
However, considering mules as a machine for giving birth to offspring is undoubtedly cruel .
Although biological experiments are not explicitly prohibited, animals should be treated well in experiments and protected as much as possible.
This is not only a respect for life itself, but also the responsibility of human beings as higher intelligent creatures.
Back to the topic, the emergence of mules is a challenge to the "red line" of nature to a certain extent, but unfortunately it is not successful. The red line of
is reproductive isolation . Over countless years, the creatures in nature have been bound.
Do you think this is a donkey or a mule?
Reproductive isolation in nature
The so-called Reproductive isolation is that different species or the same species that are not closely related to cannot mate and reproduce. Even if offspring is reproduced, the ending is a tragedy.
What makes people wonder is where reproductive isolation comes from and why does it restrict the evolution of organisms?
Scientists do not know the answer to this question, but it can be clear that the benefits of reproductive isolation to species are greater than its own disadvantages.
The reason is that the reproduction of different genes is instability. If there is no restriction, the offspring produced by various species are strange and do not have a fixed development direction, which is not conducive to the continuation of genes.
Mules were thus deprived of their reproductive rights
and random hybridization can easily lead to the loss of certain genes .
is also due to reproductive isolation. The species on earth we live in are complex, but the division is clear and everything is developing in an orderly manner.
