Or use it to wipe your eyes, show your rival in love, use it to say hello, walk, etc ... Compared with the strange long nose, many people don't know that elephants are the only mammals with chins besides humans. What's more strange is that the elephant can evolve such a long nose, which has a deep relationship with its chin. And all this has to start with the prehistoric extinct elephant ancestors.
Speaking of the ancestors of elephants, many people may think of the ancestor elephants that appeared 47 million years ago. From the outside, it looks like a combination of tapir and hippopotamus, only the size of a pig. It doesn't have the long nose of a modern elephant, but its nostrils and lips are connected and it can skillfully search for food. Therefore, it is considered as the embryonic form of the elephant trunk.
But also because its teeth are similar to those of modern elephants. So people mistakenly thought it was the most primitive ancestor of modern elephants at first, but in fact it was just an extinct branch of ancient elephants.
* Note: At present, there are only three kinds of elephants in the world, namely Asian elephant, African grassland elephant and African forest elephant. In addition, the other elephants mentioned in the article are extinct.
After another 6.5438+0.2 million years, an ancient mastodon with a deciduous tooth appeared. At present, scientists believe that the ancient mastodon is the true ancestor of the elephant. At that time, this kind of elephant lived near the Sahara desert in North Africa today. However, in those days, the desert area without water was actually a large swamp.
This means that most of the earliest ancestors of elephants lived in water. On this basis, the theory of diving breathing appeared to explain the existence of elephant trunk. In order to swim in the swamp, elephants have evolved a nose that protrudes forward in order to reach out of the water for air.
However, with the change of forest climate, such as the disappearance of forests, the gradual drying up of oceans and rivers and other geographical factors. These ancient elephants have to live on land, but their noses still exist.
This assumption is the most reasonable explanation at present, but it still doesn't solve a problem. That is why the elephant's nose is getting longer and longer.
According to the fossil restoration map, the ancient mastodon, the ancestor of the elephant, had a short nose. On the contrary, its flat lower teeth are like a huge shovel, very sharp. Scientists speculate that their lower tooth structure is convenient for picking up plants in the water when foraging in swamps.
In fact, when the ancient elephants moved to live on land, the situation changed. Generally speaking, herbivores on land need to be much taller than carnivores. Because it helps to pick leaves and other plants in higher places. In order to survive, elephants have to make appropriate changes. As a result, the elephant grows bigger and bigger, and its head is farther and farther from the ground.
What if you want to eat delicious grass on the ground? Can't give up urgently? Many animals, such as horses, cows, giraffes and camels, do this by stretching their necks. Because long necks can ensure that their mouths can reach the ground and don't eat grass on the ground. In this way, high and low food can be enjoyed well.
Compared with other animals, the elephant's head is heavier. If your neck is long, you have to have strong neck muscles to raise your head. By that time, with its sharp teeth, the weight of the head was almost hundreds of kilograms. If it always uses its neck heavily, it must be equipped with a crane on its shoulder. Since this road is impassable, those ancient elephants have to find another way.
So let's see how extinct elephants evolved. They chose a very simple and rude method. Bad neck? Then try to lengthen your chin. So, they gradually lengthen their mandibles, so that they can reach the food on the ground. Some elephants have long and wide jawbones and a pair of thick fangs.
An extreme example is a very strange elephant that appeared in Miocene. Its jaw is extremely slender, with a pair of flat lower incisors lined up at its front end.
Because it looks like a big shovel, it is named shovel tooth elephant. Its strange mouth looks like a mixture of ducks, wild boar and mussels. At first, people thought that the shovel elephant was foraging in mud and swamp. However, studies have found that shovel-toothed elephants, like modern elephants, eat from trees.
Observing this shovel tooth through a microscope, scientists found that the shovel tooth left no trace. On the contrary, there are many traces similar to the friction of bark and branches.
When you see this, do you think of a dead creature that bites branches with its toot? I'm afraid this strange picture will make people lament the difficulty of survival. This profile shows that the elephant's chin is still very useful. Almost at the same time as the shovel-toothed elephant, the horror evolved in another direction. Yes, it is a frightened elephant with only two long lower teeth. Horror elephants lived in Asia, Europe and Africa from Miocene to Pleistocene, with the largest individual reaching 12 tons and a body length of nearly 8 meters.
Different from the modern elephant, the ivory growing on it does not grow forward, but bends to the ground like a hook. So, what's the use of this short and curved ivory?
In the final analysis, we still have to solve the problem of eating. Scientists speculate that fear of elephants may be used to push ivory onto branches to eat leaves or dig bark. For the ancestors of modern elephants-ancient mastodons, their longer and longer chins began to affect their mobility. Heavy head, long fangs and short nose make the elephant's center of gravity move forward.
To keep their heads vertical, they often need to consume a lot of energy. The longer the chin, the bigger it will be, and it can't support the weight of the elephant.
What is more difficult is that the elephant can't reach the leaves on the tall tree because of its heavy head. At the same time, their huge chins prevent them from eating grass on the ground. They can't live with it. They have to find a way to reduce the weight of their heads and shift their center of gravity back. So after generations of evolution, the elephant's head and chin have become shorter and shorter. The nose connected with the upper lip becomes longer and more flexible.
Elephants with long noses lost their competitive advantage before evolution. Climate change made their living environment worse and worse, so they gradually became extinct.
In any case, the elephant's nose has experienced a process from scratch, from short to long. This is a slender and developed nose like a modern elephant. Although the elephant's nose is very soft and flexible, it can hold 40 thousand muscles. Maxillary nerve and facial nerve form a unique long nasal nerve, which makes it the most powerful organ in elephants. The elephant's nose can do many things through precise and coordinated muscle contraction. It can lift hundreds of kilograms of heavy objects and wipe its eyes very gently.
Then, who can answer the lyrics in crayon Shinchan: "Elephant, elephant, why is your nose so long?" A paper published on 20 15 holds that a long nose is the key to keeping an elephant's figure.
Generally speaking, the energy consumed by metabolism is also positively correlated with body shape. The bigger you are, the more you need to eat, otherwise you will easily starve to death. Researchers believe that the elephant's nose is equivalent to a soft mouth, which can increase the disposable food intake of the elephant and make it commensurate with its weight. Not only that, but also greatly improved the eating quality of elephants. Because elephants are huge, they usually choose larger plants. But with the increase of plant volume, the leaf proportion and nitrogen content will decrease. If you only eat it all at once, the efficiency of nutrient intake is very low. This requires them to choose the most nutritious leaves through their noses before eating.
In this respect, the elephant's mouth alone can't do it. Only a flexible organ like the trunk can act as a soft mouth. Because of soft tissue, it is difficult to leave fossils. So there is still not enough evidence to prove that it determines the evolution of the elephant trunk. But this is also the most reliable hypothesis so far, and scientists are working hard for it.
The article was transferred from Zhihu @SME intelligence agent.