Why does a giraffe have a long neck? It would seem that the answer is obvious. It was given at the beginning of the 19th century by the outstanding French naturalist Jean-Baptiste Lamarck. He claimed that the giraffe created this miracle of nature for himself thanks to his excessive zeal. Animals from generation to generation reached up to eat the crowns of trees. So they got a long neck, which was passed on to their descendants.
Everything seems to be logical, but... Lamarck was deeply mistaken. In general, the neck of a giraffe - perfect example how science develops. Its main principle is to doubt everything, especially the obvious. Therefore, in each answer, scientists immediately look for a new question. In such a series of "question - answer - a new question - a new answer, and so on" science cognizes the world. And she proved that Lamarck was wrong, that no matter how many hundreds of thousands of years giraffes have been reaching for leaves located at a height, this has nothing to do with their long neck. In fact, genetics and natural selection are to blame for everything. Thanks to mutations, different animals were born: with just a long neck, with a longer one, and also with a very long one. And then natural selection came into play: out of this multitude of giraffes with necks of different lengths, the long-necked ones won. They ate better, as they reached for leaves that were not available to others. They were healthier, more competitive, had more offspring with the same long necks.
This is one of the most famous examples of how natural selection works, and giraffes, with their amazing necks, have made their way into all textbooks. It would seem that here you can put an end to it, but science has not calmed down this time either. She asked herself a new question: is it only in the unattainable leaves? Various versions have been proposed. Let's say this: a long neck was primarily needed by male giraffes. The "record holder" more easily defeated an opponent in a fight for a female, or maybe the weaker sex for some reason preferred longer-necked males. In other words, giraffe neck length was a trait on which sexual selection worked.
Another hypothesis: a long neck protects against overheating. After all, the temperature balance depends on the ratio of the surface of the body to its volume. The larger the surface, the faster the heat escapes, the larger the volume of the body, the more heat is retained in it. For a large animal in a hot climate, it is important to get rid of excess heat so as not to overheat. Perhaps the long neck, along with the long legs of giraffes, increase body surface area relative to volume, helping them to cool. Scientists from South Africa made calculations and showed that the surface-to-volume ratio of a giraffe is about the same as many other animals. This means that the "refrigerator neck" hypothesis will have to be discarded. But the authors immediately put forward a new version: a giraffe can escape from overheating by always positioning its head towards the Sun. So they reduce the area of \u200b\u200bthe body illuminated by its rays - the light simply does not fall on the neck. Quite possible.
No other animals have such unique genes, except for the giraffe.
Studying the phenomenon of the giraffe, scientists came to the conclusion that the long neck "pulled" changes in many of its organs. To pump blood to a height of 5-6 meters, nature provided the animal with a very powerful heart. It passes 60 liters of blood per minute, weighs 12 kg and creates a pressure that is three times higher than that of a person. This is big job even at rest, but giraffes also love to run, they reach speeds of up to 60 km / h, which is simply amazing with their growth. And for this they had to greatly change their constitution: the back is sloping, the torso is shortened, and the legs are greatly elongated. This means that not only "neck" mutations worked on the structure of the giraffe, but many others. Which? This question was answered by an international group of scientists. They compared the genomes of the giraffe and its closest relative, the okapi, which did not look like him at all. Despite the fact that by evolutionary standards they diverged relatively recently, only 11-12 million years ago, the okapi is more like a zebra - it has neither an elongated neck nor a strong heart that allows it to pump blood to great heights. The genes of several dozen other animals, from mice to cows, have also been studied. As a result, it turned out that about 70 genes that both humans and other mammals have are “tuned” differently in the giraffe. No other animals have such specific variants. Moreover, it is these genes that are responsible for the development of the skeleton and the cardiovascular system.
Now scientists intend to go further, to understand which particular of this ensemble of 70 genes caused the appearance of a long neck. To do this, giraffe genes will be introduced into the mouse genome. When long-necked rodents are born, it will become clear which gene has turned the giraffe into a natural wonder.
The giraffe is an amazing animal, very graceful, with thin legs and a high neck. It is very different from other representatives of the animal world, especially in its growth, which can exceed five meters. This is tallest animal among those living on land. Its long neck is half the total body length.
Interest in the giraffe arises in both children and adults, why does he need such long legs and neck. It is possible that there would be fewer questions if animals with such a neck were more common in the fauna of our planet.
But giraffes have other body structure features that are very different from other animals. The long neck consists of seven vertebrae, exactly the same number in any other animal, but their shape is special, they are very elongated. As a result, the neck is not flexible.
The heart is large, because its task is to supply blood to all organs, and in order for the blood to reach the brain, it must be raised by 2.5 meters. Blood pressure giraffe almost twice as high than in other animals.
The lungs of a giraffe are also large, approximately eight times more than an adult. Their task is to distill air along a long trachea, the respiratory rate is much less than that of a person. And the head of a giraffe is very small.
Interestingly, giraffes sleep most often standing up, laying their heads on the croup. Sometimes, to rest their legs, giraffes sleep on the ground. At the same time, it is rather difficult for them to find a place for a long neck.
The peculiarity of the body structure of the giraffe is associated with nutrition, which is based on young shoots, leaves and buds of trees. The trees are quite tall. Such food allows you to survive in hot conditions, where there are many grass-eating animals and in summer, the savannah is completely burned out. So it turns out that giraffes are in more favorable conditions.
Giraffe's favorite food is acacia.. The animal grabs the branch with its tongue and draws it to the mouth, plucks the leaves and flowers. The structure of the tongue and lips is such that the giraffe cannot damage them on the thorns of the acacia. The process of nutrition takes him sixteen or more hours a day, and the amount of food is up to 30 kg. A giraffe sleeps for only one hour.
A long neck brings a lot of problems. For example, to just drink water, a giraffe spreads its legs wide and bends over. The pose is very vulnerable and at such moments the giraffe can easily become a prey for predators. A giraffe can go without water for a whole week, quenching its thirst with the liquid present in young leaves. But when he drinks drinks 38 liters of water.
Since the time of Darwin, it has been believed that the giraffe's neck acquired its size as a result of evolution, that giraffes in prehistoric times did not have such a magnificent neck. According to the theory, during the drought, animals with a longer neck survived, and by inheritance they passed this feature on to their offspring. Darwin argued that any hoofed quadruped could become a giraffe. Quite a logical statement, within the framework of evolutionary theory. But fossil evidence is needed to confirm it.
Scientists and researchers should find various transitional forms. However, the fossil remains of the ancestors of today's giraffes are not much different from those living today. And transitional forms from a short neck to a long one have not been found so far.
The giraffe is an animal with thin legs and a long neck, graceful and very amazing. Its growth can sometimes reach more than 5 meters, and in this it is very different from other animals. The giraffe is the tallest animal on land. Half overall growth a giraffe is only one of its necks!
The question "Why does a giraffe need legs and a neck of such length?" hurts people of all ages. But if there were more animals with such a long neck on Earth, the answer to the question would be obvious. Giraffes also have other distinguishing features of the body structure, which is not similar to the bodies of other animals. Its neck is formed by a system of seven vertebrae, like in other animals. But the shape of the giraffe's vertebrae is not like the usual ones. They are very elongated. It is because of this that the giraffe's neck is not as flexible as, for example, ours.
You already know that the task of the heart is to provide blood to all the cells of the body. In order for blood to enter the brain of a giraffe, it must be raised to a height of more than two meters. Only a big heart can do this task. For this reason, the blood pressure in these animals is almost twice as high as in others.
A giraffe breathes much more slowly than a human, but that doesn't stop it from having incredibly large lungs. Compared to a human, their volume is almost nine times greater than ours. Their purpose is to circulate oxygen through the trachea, which is located in the neck.
You will be surprised, but giraffes sleep standing up. They lay their heads on their backs and fall asleep. But sometimes, if their legs are tired, they can fall asleep on the ground. With this way of sleeping, it is difficult for them to find a comfortable position for the neck. Another amazing fact: a giraffe's sleep lasts only one hour!
Scientists have proven that the structure of the body of a giraffe is directly related to its nutrition. He eats leaves and branches from trees. And since in hot conditions not only the giraffe feeds on plants and grass, its long neck is indispensable for obtaining food. Thus, the giraffe is in the most favorable conditions than other inhabitants of arid places.
The most favorite delicacy of these animals is the acacia. But its spines are not able to harm the giraffe, because it has a special structure of the oral cavity. The giraffe loves to eat. This process lasts for more than fifteen hours every day, and all the food can weigh more than 30 kilograms.
But a long neck is not only positive sides, but also negative. For example, to drink liquids, a giraffe needs to spread its legs and bend down to reach the water. In this position, the giraffe becomes very vulnerable, and predators can easily cripple it or even kill it. For this reason, the giraffe is able to live without water for almost a week, taking fluid from leaves and plants. But when he has the opportunity, he can drink more than 35 liters of water!
Are you wondering why the giraffe's neck has become so long? Scientists are sure that this happened in the course of evolution. During a drought, animals with a long neck were more likely to survive, which was passed on to their descendants. Then there must be transitional forms between modern giraffes and their ancestors. But, unfortunately, no such animal has yet been found.
Previously, they thought that for food, to get tree branches and eat them. It turned out - for sexual sex. Not for the act itself, but for the disco scuffle that preceded it. True, this is still a hypothesis.
Most of us are used to thinking that giraffes need a long neck in order to get food from the tops of trees. But, as the observer learned, some scientists believe that this anatomical feature is more likely related to the sexual life of these animals.
Giraffes are the tallest living land mammals, and their long legs and neck make them seem especially huge. Males can reach a height of 5.5 meters, females are usually a little lower. In their natural habitat, these beautiful creatures crane their necks to pluck leaves from the tops of trees.
The giraffe lives "in places where the soil, almost always dry and devoid of grass, forces it to pluck leaves from trees and make constant efforts to get them," he wrote in 1809 in his book "Philosophy of Zoology."
“As a result of this habit, preserved since ancient times by all individuals of this breed, the front legs of the giraffe became longer than the hind legs, and its neck [...] stretched out.”
In general, according to Lamarck, the giraffe's long neck was formed due to its constant stretching and inheritance of this anatomical features for many generations. English naturalist Charles Darwin also believed that such unusually long legs and neck must be associated with the need to get food.
“The giraffe, by virtue of its high stature, very long neck, forelegs, head and tongue, has a general constitution remarkably adapted to picking leaves from the upper branches of trees,” says his book On the Origin of Species, published in 1859. However, Darwin did not accept Lamarck's ideas about the causes of this evolutionary change. In his opinion, the long neck of the giraffe is the result of continuous "natural selection". Long-necked giraffes had a better chance of surviving hard times than their short-necked rivals.
It is now clear that Darwin generally correctly understood the principles of evolutionary development, while Lamarck was mistaken. Therefore, it is important to understand the difference between the evolutionary mechanisms described by both scientists. It is a pity, however, that for illustration it is necessary to use a giraffe.
To begin with, Lamarck mentioned the giraffe only once and in passing in one of his many works. However, it is precisely for this that he is remembered, and not at all for the ideas that served as the forerunner of the theory of evolution and greatly influenced Darwin, and for the rest of his contribution to the development of science. In addition, the hypothesis that the long neck was formed in giraffes for the sake of prey, which was put forward by both Lamarck and Darwin, may not be entirely correct.
In 1996, zoologists Robert Simmons and Lew Scheepers came up with several theses that called into question the existing theory, known as "competition for food."
“During the dry season (when the struggle for subsistence should be in full swing), giraffes usually feed on foliage from low bushes, and not from tall trees,” scientists say in their article, published in the American scientific journal American Naturalist . Moreover, most often giraffes eat with their necks bowed - by the way, this happens faster.
It is also not clear why for over a million years the growth of the giraffe has remained two meters more than all of its rivals. This is an obvious overkill.
Simmons and Scheepers came up with an alternative suggestion that the long neck is the result of sexual selection, which became known as the "neck for mating" hypothesis. Male giraffes often fight over the location of females - this ritual is called "fighting with necks." Opponents stand side by side, and then begin to clobber each other with their heads.
"Giraffes strike an opponent in the neck, chest, ribs, or legs, using the top or back of their hard skull as a club, with a force capable of knocking the opponent down or incapacitating him," write Simmons and Scheepers.
“Apparently, the skull of the male giraffe is perfectly adapted for such a specific fight with their relatives,” note the authors of one study, the results of which were published in 1968.
According to zoologist Ann Innis Dagg of the University of Waterloo in Ontario, Canada, who has been studying giraffes since the 1950s, battles (even a fatality was recorded in the 1960s) are usually won by the largest males, who produce the most offspring. "The rest of the giraffes don't have many mating opportunities." In addition, there is evidence that females are more accommodating to courtship by larger males.
However, over the past decade, evidence has been collected that argues against the “neck for mating” hypothesis. In particular, a 2013 study found no evidence that males have a longer neck (relative to body weight) than females.
In other words, there are no obvious signs of sexual dimorphism in the length of the neck. As a result, the authors of the study came to the conclusion that after all, "the hypothesis of competition for food is a more likely explanation for the high growth of giraffes." Meanwhile, other scientists have found direct support for the "competition for food" hypothesis.
By building fences around acacia trees in South Africa, Elissa Cameron and Johan du Toit were able to demonstrate that when competing for food with smaller giraffe rivals such as Steinbock, impala, and kudu, “giraffes gain a nutritional advantage because they can get leaves.” inaccessible to smaller animals. That's what it says in a magazine article. american naturalist in 2007.
Their findings provide "the first experimental evidence that the giraffe's extremely elongated body is the result of natural selection, having evolved in response to competition from smaller herbivore species." These studies suggest that Darwin and Lamarck were right after all.
However, proponents of the “neck for mating” hypothesis do not give up, so it is possible that there is some truth in both explanations. One way or another, this story may not be over yet...
Like humans, giraffes have seven vertebrae in their necks. But, nevertheless, it is much longer than ours. This is due to the fact that the third cervical vertebra of the animal is almost the same length as the bone connecting the shoulder and elbow joints of a person. At the same time, its width is almost 9 times less.
Giraffes did not immediately get a long neck
According to a new study published in the Royal Society open sciences, elongation of the giraffe's neck occurred gradually. The process took at least two stages. First, the cervical vertebrae stretched towards the head and only millions of years later - towards the tail.
Why giraffes have such a long neck is a question that has been debated by scientists for a long time. According to some assumptions, this makes it easier for animals to obtain food in the form of tall plants. Proponents of a different opinion believe that such a body design may have been formed for a protective function. 
Scientists have identified two periods of animal development
To study exactly how the animals received such an acquisition, a team of scientists led by Melinda Danowitz from the New York College of Osteopathic Medicine analyzed 71 vertebrae. Samples of representatives of 11 different species of giraffes were subjected to the study. Among them were the vertebrae of nine extinct and two living groups of animals. These fossil bones have been housed in museums around the world, and some have been discovered over a century ago. 
“The most interesting thing is that the length of the neck of a giraffe that lived many years ago does not correspond to the size of the neck of a modern animal,” said Nikos Solonias, one of the co-authors of the study. He also added in his statement: “Firstly, in early period species, only the anterior part of the third vertebra is elongated. Those bones that were a little “younger” turned out to be larger. They have already gone through two stages of their development and have been elongated both towards the head and towards the tail.
On the other side of the era
The upper end of the vertebrae originally elongated about 7 million years ago. This type of animal, called Samotherium, has already become extinct. This representative of artiodactyls is the most distant relative of the modern giraffe. The second stage in the development of the animal - the elongation of the vertebra in the tail - occurred much later, about 1 million years ago. 
The team also found that the most primitive giraffe appeared with a slightly elongated neck. As Danowitz noted, the first signs of elongation of the vertebrae could appear as early as 25 million years ago. In this case, it is quite realistic to consider the so-called Prodremotherium as the ancestor of the giraffe.
