The Evolution of Horseshoe About 65 million years ago, an asteroid with a diameter of 10 km broke into the earth's orbit, causing tsunami, earthquake, volcanic eruption and other natural disasters, leading to the extinction of dinosaurs. However, mammals have a wide range of energy sources because of their insectivorous and omnivorous nature. Coupled with small size and low energy demand, mammals survived extinction and gradually flourished.
Due to the extinction of dinosaurs, most of the ecological niches on the earth were vacated, and mammals began to fill the gap. Among them, not only carnivores but also herbivores appeared, and the ancestors of Chiroptera were one of them.
From Paleocene to Eocene, because the carbon dioxide content of the earth reached a critical value, the temperature of the earth soared in a short time. The high temperature climate makes the earth's water source evaporate a lot, and then falls to the earth in the form of rain. In this hot and rainy weather, the forest is gradually flourishing. Even in the polar regions, there are no permanent glaciers, but a large rainforest.
For the ancestors of Chiroptera, the plants in the rainforest are fresh and juicy, and the scattered trees can provide them with better shelter, and Chiroptera is gradually flourishing.
However, the environment of the earth is not static, and a catastrophe is coming. For some reason, the earth suddenly cooled down, which caused the original ocean current to be broken, the earth's rainfall decreased, and the air became much drier.
Many forest vegetation is no longer suitable for growth. On the contrary, grasses thrive. Perhaps for us, whether it is leaves or grass, it is a plant. For Chiroptera, no matter what plants you eat, the prosperity of grass can also satisfy the survival of Chiroptera.
But this is not the case. Herbs are low, mixed with a lot of sand and stones. In addition, the leaves of herbs are hard, which makes it difficult for Chiroptera to adapt to this change, so a large number of Chiroptera became extinct during this period.
In order to adapt to this environment, the surviving Chiroptera evolved high crown teeth, that is, the teeth are super long and can be worn for a lifetime. In addition, because there is no shelter in the grassland, carnivores can easily find them. In order to avoid predators, some Chiroptera began to evolve hooves, while horses were more extreme. They only have one middle finger, and the middle finger has evolved hooves, while the other toes have degenerated. This way of walking greatly improves the horse's grip on the ground and makes it run faster.
Because a horse has only one horseshoe, humans can install horseshoes on its horseshoe, but it will not affect its walking. Horses' hooves are equivalent to human nails and will grow with the growth of horses. The reason why human beings put horseshoes on horses is that after human beings domesticate horses, they need to rely on horses to carry heavy objects and act as means of transportation.
Due to the long-term consignment of heavy goods by horses, the horseshoes are seriously worn. If the horseshoe is not corrected for the horse, when the horseshoe is put on the horse's foot, the horse will be unable to walk because of eating pain, thus delaying the progress of mankind.
Why don't cows nail their claws? Cows are herbivores like horses, but they are distant relatives. They belong to the order Artiodactyla and have even toes.
Cattle and horses have different evolutionary paths, and the main difference is hooves. Cattle have multiple hooves, so they are called Artiodactyla, while horses have only one hoof, so they belong to Artiodactyla.
The two hooves of cattle can be separated or gathered together when walking, so it is difficult for people to install hooves for them.
Moreover, cattle in our country are mainly used for farming, rather than carrying heavy objects, so the hoof of cattle wears slowly, and even if it is not installed, it will not cause serious harm to cattle.
At present, in many places, the way cattle cultivate land has been abolished, but cultivated by machines, so the burden on cattle has become less. Now people raise cattle not for breeding, but for meat quality and milk, so cattle don't need nail protection.
In fact, some horses used for breeding do not nail horseshoes. This is because horses used for breeding rarely participate in transportation and supervised work, but are kept in stables. They don't walk and consume many horseshoes every day, so these horses don't nail horseshoes. But sometimes horseshoes grow too long, and long-term neglect affects walking.