Help on Tele2, tariffs, questions

Giraffes are hard to miss. In zoos or in their natural habitat - Central Africa - they tower above other animals. Still would! After all, the giraffe is the tallest land animal on the planet. The length of the giraffe's neck has puzzled nature researchers for many years. You often hear: “Where do they get such a long neck?”

Looking at how a three-meter (not counting the neck!) animal stretches out its neck, the length of which is 2.5 meters, and then sticks out its tongue, another thirty centimeters long, reaching a seemingly inaccessible acacia branch, you might think that giraffes “grew” themselves such a long neck as a result of long exercises. But is a giraffe really able to somehow influence? Doesn't a change in one trait affect the body as a whole? Let's take a closer look at the giraffe...

The giraffe is a mammal, and therefore its anatomical structure should be similar in many ways to that of other mammals. Like the vast majority of animals, the giraffe has seven cervical vertebrae. What if he didn't have those seven links between his shoulders and the base of his skull? The giraffe's huge head must remain at the top at all times. When a giraffe stands, almost half of its 225-pound neck muscles are in tension. And muscle mass is directly related to the number of joints it needs to support. If, for example, there were only two joints - on the skull and on the chest - the weight of the animal would be much less, and less energy would be required for its life. And if the lack of food resulted in a change in the structure of the neck, then wouldn't this evolutionary process also change the number of cervical vertebrae and joints? Of course, the problem with such a design would be a loss of flexibility and a sharp weakening of resistance when hit on the head or neck.

In contrast, a neck with more joints would require more energy and more muscle mass. This would lead to a forward shift in the center of gravity of the giraffe's body; consequently, the head would also stretch forward, and the hind legs would lift off the ground - of course, provided that the front legs were able to withstand this. So seven cervical vertebrae is an excellent design solution.

Because the giraffe's head is so high, its huge heart must be able to pump enough oxygen-rich blood to the brain (to a height of 3 meters). Given the high blood pressure, this could cause serious problems when the giraffe lowers its head (say, at a watering hole), if not for the unique system of arteries with thickened walls, various valves, a network of tiny vessels (rete mirabile - "wonderful network") and receptors , assessing blood pressure. With their help, blood flow in the giraffe's neck is regulated depending on pressure. Even to those who consider this entire system to be merely “an adaptation to high pressure in the blood vessels,” the giraffe seems to be a unique creature.

The giraffe has perhaps the strongest heart in the animal kingdom because it needs blood pressure almost twice as high as normal to move blood up the neck to the brain. With such pressure, only very unusual structural features save the giraffe from hallucinating when it tilts its head at a watering hole.

No less surprising is the fact that the giraffe’s blood does not accumulate in its legs, and the giraffe does not bleed after injuring its leg. The answer to this secret lies in very strong skin and internal ligaments that ensure the integrity of blood vessels and normal blood flow. The structure of giraffe skin has become the subject of intensive study by NASA specialists in connection with the development of new space suits. In addition, all the arteries and veins on the giraffe’s legs are located very deep, and this also prevents bleeding. The capillaries that approach the surface of the skin are very small, and the red blood cells of a giraffe are three times smaller than those of humans; Thanks to this, they pass through narrow capillaries. Obviously, these unique features of the giraffe's anatomy are interrelated with the length of its neck.

But that is not all. Small red blood cells have a relatively large surface area; they absorb oxygen from the lungs better and faster. This helps to effectively supply oxygen to both the limbs and the head.

The lungs, working in harmony with the heart, provide oxygen to the tissues, but the giraffe is unique in this sense. His lungs are eight times larger than those of a human, and his breathing rate is three times less.

Such slow breathing is necessary so that the ribbed four-meter trachea does not become weathered when moving huge masses of air. Why does a giraffe have such big lungs? After inhaling, no animal is physically able to exhale completely. The giraffe's problem is complicated by the fact that the long trachea creates a very large volume of "dead space" air - more than a person can inhale at one time. To compensate for this, you need to increase the volume of your lungs - then the air in the “dead space” will make up a small part of the total air in the respiratory tract. And this physical problem has been successfully solved in the giraffe’s body.

The miracle of the giraffe's birth bears the indelible stamp of intelligent design. A newborn is born falling from a height of one and a half meters, since the mother cannot squat on half-bent legs, and lying on the ground means inevitably becoming the prey of a lion or other predator. Moreover, the cub’s head, like that of other animals, is disproportionately large, which complicates childbirth. But the main thing is that this head is connected to the 70-kilogram body through a fragile long neck. And if a newborn falls head first, then when the body falls from above, the cub will inevitably break its neck; and if his body is forward, then he will still break his neck under the weight of the weight of the body, when it has already come out, but his head has not yet. However, there is a way out of this situation: a newborn giraffe has very narrow hips on the hind legs, and the neck is long enough so that the head runs along the body to the hips. Thus, the hind legs come out first, the newborn rests on them, his head is supported by the hips, and the neck, thanks to its extreme flexibility, remains intact.

Such a miracle becomes possible only with a combination of strictly defined structural features and precisely this length of the neck. A few minutes later the newborn is already standing in a graceful pose between the mother’s legs. In the four years from birth to maturity, the giraffe's neck grows from one-sixth to one-third of the animal's total height. Thanks to this feature, the giraffe quickly gains the ability to lean toward the water while standing on its long legs. In the first year of life, a young giraffe feeds almost exclusively on its mother’s milk, and this is not difficult.

From an ecological point of view, the giraffe fits perfectly into its environment. Fast-growing trees create too much shade and thereby destroy the grass that serves as food for other savanna animals, so such trees need to be “trimmed.” In addition, herbivores need a “sentinel” who can spot silently sneaking predators from the cat family in the tall grass. The giraffe is perfect for this role not only because of its height, but also because of its excellent eyesight and behavioral characteristics. Having warned other animals about the threat with several flicks of its tail, it fearlessly goes out to meet danger. Huge height, tough skin, deadly force of the hind hooves and swift gait make the adult giraffe a very unattractive prey for any predator.

Of course, the giraffe’s neck became long not because its ancestors had to constantly reach for leaves. So how did it all go?

During the early Neogene there was a flourishing of fatty species, twhen they reached their greatest number of species and geographic distribution. Many of them (species) were already distinguished by their large size and powerful physique. As a result of climate change in the Pleistocene, most giraffes became extinct, leaving only twotemporary species: giraffe and okapi. They still had short necks, but over time, thanks to mutations in giraffes, their necks became

will lengthen giving a number of advantages.

According to one version, authored by zoologist Rob Siemens, long necks arose as a result of fightingnecks. A male with a longer neck was more likely to win and, as a result, received more “attention” from females, resulting in more offspring.

It should also be added to Siemens’ version that the long neck gave an advantage in searching for food; they could pluck the tops of trees, which means they found more food for themselves and had a better chance of surviving, especially during periods when food was scarce andhad to compete with other herbivores: antelopes, zebras and many others. And each of them has to dine on his own “floor.”

It is inconvenient for a giraffe to pluck low-growing grass, but he can easily reach the very tops of trees, and at such a height he has no competitors. (Giraffes also often preferThey move to improve their ownsafety with herds of antelope or zebra. Here they also need a long neck to avoid competition for food) The giraffe rarely nibblesstumpy grass, preferring only succulent shoots that are rich in moisture. Getting all the necessary liquid from food, giraffes can be quite far from water sources.

Just as they claimzoologists from the Wildlife Research Center in South Africa and the American University of Wyoming, the advantage of long-necked animals is that they can see further (giraffes can see their tall relatives at a distance of up to a kilometer), thereby increasing their ownIncreased safety, as well as a long neck, improves thermoregulation due to an increase in body surface area.

Well, okay, but besides the advantages there are also disadvantages, like a predatorAnd? After all, with a long neck, a giraffe is more vulnerable. Giraffes can run fast and, in case of urgent need, reach a gallop speed of 55 km/h, that is, over short distances they can outrun a racehorse.

It is also noteworthy that these, at first glance, are bulky and awkwardlow-tide animals can also jump, overcoming even barriers 1.85 m high. Well, if you have to clash with an enemy face to face, then he defends himself quite effectively with strong blows from his front hooves, capable of crushing the skull of anyone notto a cautious attacker.

Due to its size, the giraffe has few natural enemies, and from those few predators that dare to attack it, it defends itself quite effectively with strong blows from its front hooves, capable of crushing the skull of any neophyte.to the rogue attacker.

Great, we figured out the neck, but what about blood circulation, especially in relation to supplying the brain, with such and such a neck?

Giraffes have especially strong hearts. It passes 60 liters of blood per minute, weighs 12 kg and creates pressure thatthree times higher than in humans.
However, it would not be able to withstand the overload of the sudden lowering and raising of the giraffe's head. To ensure that such movements do not cause the death of the animal, shelterThe giraffe's body is thicker and has twice the density of blood cells than humans. In addition, the giraffe has special shut-off valves in the great jugular vein that interrupt the flow of blood so that pressure is maintained in the main artery supplying the brain.

Children's regional public "Learned society of students "Search"
Municipal state educational institution "Goryacheklyuchevskaya
secondary school of the Omsk municipal district of Omsk
region"
XX Municipal Scientific and Practical Conference of Schoolchildren
Non-profit educational institution "Search" of the Omsk municipal district
Topic: “Why does a giraffe have a long neck”
Educational and research work
Scientific direction "It's interesting"
Performed:
1st grade student
MKOU "Goryacheklyuchevskaya Secondary School"
Rykovskaya Taisiya Petrovna
Scientific adviser:
primary school teacher
MKOU "Goryacheklyuchevskaya Secondary School"
Krasilnikova Olga Viktorov
1

Omsk 2013
Content
Introduction………………………………………………………………………………………. 3
1.Who is a giraffe?………………,……………...…………………………… 5
2. Friends and enemies of the giraffe……………………………………………………….6
3. Interesting things about giraffes……………...……………………………………………………………….7
4. So why does a giraffe have a long neck?................................................. ............................8
Conclusion……………………………………………………………………………………… …9
List of references……..……………………………………………………........10
2

Introduction
Recently, together with my parents, while on vacation in Thailand, I visited
open zoo in Bangkok, where I saw and even fed very interesting things
animal - giraffe. The first thing that immediately caused my surprise and what I shouldn’t
I had to look away, it was the long neck of giraffes. (Slide 2)
Picking flowers is easy and simple
Small children
But to the one who is so tall,
It's not easy to pick a flower! ­
I remembered the poems of S. Marshak. I decided to find out: why does a giraffe need such
long neck, doesn't it bother the animal?
I asked my parents, they advised me to try to find the answer myself.
to this question. I asked my classmates if any of them knew:
why does a giraffe have a long neck? They didn't know for sure, but they assumed that
long neck giraffe:
for beauty;
to pluck leaves from tall trees; The giraffe's neck bones are long.
I decided to find the answer to this question myself.
The purpose of my work: to try to find out the reason for such a long neck of the giraffe;
In the process of conducting research in my work, I set the following
tasks:
1. study the lifestyle of giraffes and their habitat;
2. learn interesting facts about giraffes;
3

3. set the value of the long neck for the animal;
4. draw a conclusion: how much does a giraffe need a long neck? (Slide 3)
Hypothesis: If I read books and other materials about giraffes, then I can
find out why he has a long neck.
Research methods:
encyclopedic literature, survey.
observations,
conversation,
scientific study,
5. Object of study: giraffe lifestyle. (Slide4)
4

Who is a giraffe?
The giraffe is an animal that lives in the savannas of Africa. They live
in herds. Very peaceful. (Slide 5)
Its enormous height reaches 6 m, and almost half of this height falls on
neck. When I fed the giraffe bananas, I especially liked his black ones,
thick, long eyelashes.
Giraffes are herbivores. Their long and flexible neck allows them
feed on leaves from the tops of trees and tall bushes - at a height where
they have no rivals. (Slide 6)
To drink water, the giraffe has to take strange poses.
Sometimes he spreads his front legs wide and tilts his front
the torso and neck forward, and sometimes the legs simply bend. (Slide 7)
Giraffes sleep in an equally interesting position. They throw their neck back and lay down
head on the back thigh. (Slide 8)
I tried to draw a giraffe myself and saw it like this (Slide 9)
5

Friends and enemies of the giraffe.
Giraffes have few enemies, as predators can attack them
only lions, and even then in a group. Other inhabitants willingly graze with giraffes
savannas - antelopes, zebras, ostriches. Giraffes, due to their high growth,
With excellent vision, they are able to see a sneaking predator from afar.
Unfortunately, humans are also a serious enemy for the giraffe. He
I have been killing giraffes for meat for a long time.
6

3. Interesting things about giraffes.
While reading about the giraffe, I learned many interesting facts about the animal. Here
some of them:
1. The giraffe is the tallest land animal on the planet.
2. The length of a giraffe's tongue is about 50 centimeters. He can use it to clean
your ears.
3. The giraffe has a very large heart, which weighs 12 kilograms.
4. Giraffes can rest while standing, sometimes placing their head between two
branches so as not to fall.
A giraffe can go without water longer than a camel. (Slide 10)
7

So why does a giraffe have such a long neck?
As you can see, the giraffe is a very interesting animal. But still, why should he
such a long neck. It’s not easy with her: it’s inconvenient to pluck grass or drink or sleep
difficult.
It's not easy being a giraffe. Not an easy matter...
A giraffe's head is far from its body.
How does he live, my God? I feel sorry for him...
How does he wash his neck in the morning with such a length? –
Yuri Beridze says jokingly in his poem. Exploring lifestyle
giraffe, I learned this:
1. The giraffe’s long neck allows it to eat leaves on the tops of trees, and it
you get untouched vegetation at the highest altitude. (Slide 11)
2. A long neck, which means tall height, helps to notice enemies from afar.
(Slide 12)
3. The giraffe's neck along with strong legs is an excellent weapon against
predators. Even lions. When hunting a giraffe, always exercise caution,
approaching him in a group. (Slide 13)
4. Even with a long neck, a giraffe cannot get food from the ground - the length of its legs
always longer than the neck. The giraffe constantly has to position its legs like
as wide as possible in order to become shorter and reach, for example, water.
8

If a giraffe's neck were short, it would have to lie on its stomach and drink
water while lying down. (Slide 14)
But it turns out that in nature there are also short-necked “giraffes” - okapi
(“forest giraffes”). They live only in the forests of the Congo, where there is a lot of greenery and they cannot
you need to stretch your neck high. But there are very few okapi. Only 20 nurseries in the world
can boast of having such a rare animal. (Slide 15)
Conclusion
After learning so much about the giraffe, I came to the conclusion that the giraffe's long neck is
This is not a mistake of nature, but an excellent adaptation of the animal to the conditions
life. Without a long neck, he would have less food and more enemies.
I shared my observations and conclusions with my classmates -
Now they also know why the giraffe has a long neck. (Slide 16)
9

Bibliography
1. Alfred Brehm “The Life of Animals.” – M: Eksmo, 2011;
2. V. D. Ilyichev, O. L. Silaeva “Giraffes” // Biology. 815.4.2003.
№14 (688);
3. S. Marshak “At the Zoo”
4. http://www.portalslovo.ru;
5. http://ru.wikipedia.org;
6. http://www.

Forum
.zoologist.ru
10

I first saw a giraffe in its natural habitat in Arusha National Park in Tanzania, and was amazed by the yellow-brown head gliding gracefully at a seemingly impossible height above the tops of the tall acacia trees. That was 11 years ago, which is roughly why the giraffe remains one of my favorite animals. But the giraffe is dear to me not only because of my African impressions.

As an evolutionary biologist and professor, I deduced Giraffa camelopardalis on stage during class - not literally - as an example of how natural selection has produced a creature that is, on the one hand, impressively adapted to its peculiar ecological niche, and on the other hand, an example of "clumsy, wasteful and inept" the process of evolution, using Darwin's words. It is sometimes suggested that these oversights are the result of mutations or evolutionary errors. But they actually arise because of history: the fact that at any point in history natural selection has no choice but to work with what is already there. More clearly than other animals, giraffes reflect the fact that organisms were not created from scratch (or if they were, then the Great Creator was very inept). Rather, they were cobbled together through trial and error from their historical predecessors.

Giraffes have long held a special place in the hearts of evolutionists, but for a different reason: as an example of how to distinguish Darwinian evolution from Lamarckian evolution. However, it turns out that the story is not that simple; indeed, nothing at all concerning these amazing and strange animals is simple. A closer look at their private lives has cast mating under suspicion, along with chewing, when it comes to their remarkable anatomy, raising questions that have fueled debate among today's (admittedly small) giraffology community.

Let's start with the most obvious. The giraffe's high stature creates a number of difficulties that have been solved with the help of remarkable adaptations. Pumping blood two meters above the heart to the animal's towering head requires exceptionally high pressure, three times the systolic level in humans. To prevent their arteries from bursting, giraffes require special support structures within their blood vessels.

In another direction, to prevent blood from pooling in the feet, which are at the end of very long legs, giraffes have evolved a type of compression stocking that humans use after surgery or to prevent deep vein thrombosis during long flights. 1 The invention of giraffes is highly elastic walls of blood vessels in combination with an extensive capillary network. By reducing the perfusion of fluid into surrounding tissues, these designs keep the giraffe's blood in the vessels where it belongs, and not in the surrounding tissues. These animals have another specially adapted compression system in the neck that prevents too much blood from rushing to the head when they bend over to drink - which they don't do very often since they get most of their water from the leaves they eat using their very flexible 45 cm tongues.

Although giraffes' necks are exceptionally long, they are actually inferior to their legs, as those colossal necks are - believe it or not - too short. In order to reach the puddle, the drinking giraffe has to spread its legs wide apart. And, by the way, the same mechanism for controlling the flow of fluids works in the opposite direction in the giraffe's neck, when the giraffe stops drinking and raises its head up, allowing a relatively small trickle of blood to flow down so that brain hypoxia does not occur. 2

The name "giraffe" comes from the Arabic word "zarafah", meaning "fast walker", and giraffes do use their long legs to walk quickly, although their long lever legs and slightly swaying, vertically balanced neck columns seem to that they are moving slowly. For unclear reasons, but presumably due to truly giraffe-like biomechanics, when giraffes need to move quickly, they do not gallop or jump like almost all other quadrupeds, which in such cases lift both their front and hind legs off the ground. Instead, they lift their front and back legs on the same side at the same time, alternating left and right - rather than back and front - in a manner called "ambling." It's actually very effective and elegant, more clunky than clunky once the observer gets used to the novelty. (By the way, camels also amble, 3 which may explain the name of the giraffe species in Latin camelopardali, due to the ancient belief that giraffes are half-camel, half-leopard, the latter due to giraffes' noticeably spotted and tile-like coloring.)

Now about that remarkable neck. How many bones are there in a giraffe's neck? Answer: seven (according to a 1999 Journal of Zoology study - eight), 4 is the same number as in humans, only the giraffe is huge, and each cervical vertebrae is on average 25 centimeters long. What about the mouse? Also seven, although - surprise - all very small. Mouse.

Detailed photo of a giraffe's neck. Photo: Mike Taylor and Matt Wedel

Probably the most well-known fact about the giraffe's neck (at least among biologists) is the peculiarity of its nerves, in particular the left recurrent laryngeal nerve, which sends impulses to the animal's larynx. Forget for a moment that giraffes are probably the quietest of the large mammals, they make sounds, albeit faintly. No one knows why they are so insinuating, although it is clear that their larynx has the same basic innervation (the connection between organs and the nervous system - approx. Newabout) as in other, noisier mammals, although the impulse travels a longer distance. Perhaps it has something to do with their long neck, or they simply have nothing to say. In any case, the muscles of their larynx - like ours - are stimulated by their laryngeal nerve, and here we have one of the most stunning examples of extremely foolish design in zoology.

The laryngeal nerves, commonly present in vertebrates, branch from the larger vagus nerve, which plays a large role in the parasympathetic system of vertebrates, which sends signals to all major internal organs, including the heart and digestive system. In all mammals, the recurrent laryngeal nerves branch from the vagus nerve at the level of the aortic arch, where the aorta—originally ascending from the heart with its branching carotid arteries supplying the neck and head—dives back to supply blood to the rest of the body. The aortic arch makes a 180-degree loop, which is not a problem for the right recurrent laryngeal nerve, which is on the "right" side, avoids the bend of the aorta and goes straight to the larynx along the trachea. However, its left companion has to bend around the aortic arch from below before heading towards the larynx. This is a little anatomically awkward, but is not a big problem for most vertebrates, including humans, since this bend only adds a few centimeters to the path.

This is both an interesting dilemma for long-necked animals and a clear example of evolution. Among modern fish and presumably the fish ancestors of modern mammals, the recurrent laryngeal nerves (left and right) ran in a straight line from the brain to the gills along the heart. In short-necked early mammals, everything was almost the same, only the left branch, passing under the bending part of the aortic arch, was slightly longer and more curved. But in those creatures that evolved to have long necks, the poor left recurrent laryngeal nerve had to take a truly absurd detour during embryonic development: exit the brain, head down to pass under that ever-retracting aortic arch, then head up again to eventually reach the larynx.

In the case of giraffes, this incongruous adaptation now requires a nerve 4.5 m long (2.3 m one way, then back), although if it ran in a straight line, the entire length would be 15 cm. Where does this strangeness come from? Because giraffes evolved from their direct ancestors, who in turn evolved from theirs, and so on to the common ancestor, the fish, the length of the recurrent laryngeal nerves of which was completely reasonable. (And by the way, don't waste all your pity on giraffes: There were other vertebrate descendants of fish - notably sauropod dinosaurs - whose 13.7-meter necks required much longer nerves: approximately 27.5 meters! In a recent technical report - in journal Acta Palaeontological Polinica, to be precise - this absurdity was called a “monument of inefficiency 5)

1. Hargens, A. R., Millard, R. W., Pettersson, K., & Johansen, K. Gravitational haemodynamics and oedema prevention in the giraffe. Nature 329, 59-60 (1987).
2. Mitchell, G. & Skinner, J.D. How giraffes adapt to their extraordinary shape. Transactions of the Royal Society of South Africa 48, 207-218 (1993).
3. Dagg, A.I. How a camel moves (The locomotion of the camel (Camelus dromedarius)). Journal of Zoology 174, 67-78 (1974).
4. Solounias, N. The unique anatomy of the giraffe’s neck. Journal of Zoology 247, 257-268 (1999).
5. Wedel, M.J. A monument of inefficiency: The presumed course of the recurrent laryngeal nerve in sauropod dinosaurs. Acta Palaeontologica Polonica 57, 251-256 (2011).<.sub>

Miracles of evolution using the example of the giraffe. Part 2

It's all very awkward so far. But why did modern giraffes develop such problematic long necks in the first place? Here giraffes help us distinguish Darwinian evolution from Lamarckian evolution. Lamarck believed that giraffes' necks became long because their ancestors stretched theirs. According to Darwin, early giraffes differed from each other in the length of their necks, and those with longer ones reproduced more successfully. According to Lamarck's concept of "inheritance of acquired characteristics" - not very different from "use it or throw it away" - organs grow larger when they are used and shrink when they are not. Almost everyone agrees that early giraffes had necks that were not very different from the necks of other ungulates.

But Lamarck and his followers imagined that these giraffes reached for ever taller leaves on the tops of savanna trees (and giraffes do indeed feed from branches), and their necks lengthened, just as muscles grow with use, until their descendants acquired the longest necks . Darwin's view is slightly different, and more accurate: with increased competition for leafy vegetation, early giraffes with slightly longer necks were able to feed themselves slightly better by reaching for high-growing leaves.

Therefore, they produced more offspring, whose necks, in turn, became longer than those of their parents. Therefore, natural selection favored longer necks, as well as necessary adaptations such as the ability to generate and withstand very high blood pressure while preventing blood from draining into the legs, plus inevitable disadvantages such as the tortuous path of the left recurrent laryngeal nerve.

But the story doesn't end there. There is another competing explanation for why giraffes have such long necks, and it involves sexual selection. First, a small digression. Although many people believe otherwise, there is no fundamental difference between natural selection and sexual selection. Natural selection occurs whenever differential reproduction occurs, in which certain genes are more successful in passing on copies of themselves to future generations. Sexual selection involves competition to obtain and acquire mates, and is as natural as other forms of selection such as foraging for food, avoiding predators, sleeping when tired, or scratching when itchy. It is simply that sexual selection sometimes results in traits - the classic example being the peacock's tail - that are ecologically disadvantageous but are nevertheless positively selected because their overall contribution to fitness through competition with the same sex or attraction of the opposite sex is greater than the direct losses. concerning simply survival.

It turns out that male giraffes are more vicious than affectionate: during the rut, they fight using their heavy, strong heads attached to long flexible necks - it turns out something like a medieval morning star or flail. And the longer the neck, the more powerful the blows. Therefore, the hypothesis - known as the "mating neck" hypothesis - states that long necks were selected because they helped males win fights with each other. Also, females may have preferred longer-necked males, in part because their offspring would then have longer necks. Accordingly, new males would compete more successfully with other males and be more sexually attractive to females of their generation. One way or another, the male genes for neck length and the female genes for choosing longer-necked mates would have been passed on. 6 This is a variant of what behavioral ecologists call the “sexual progeny hypothesis,” which also applies to the evolution of peacock tails and other seemingly odd male traits. According to this hypothesis, long necks in female giraffes are a concomitant effect of sexual selection among males.

This is a controversial idea, and the last word has not yet been said. 7 Supporting the "mating necks" hypothesis is the discovery that males with longer necks are actually more successful in combat with each other and, furthermore, giraffes actually prefer longer necks in potential mates, giving another meaning to the term necking means “kissing a clothed partner on the neck” - approx. Newabout). Additionally, most of giraffes' foraging occurs at shoulder level rather than at neck level. In addition, giraffes are two meters taller than other leaf-eating animals, suggesting that foraging competition is not the main driving force behind altitudinal evolution. On the other hand, it may be that in times of food shortage the extra growth is worthwhile, and what's more, usually the most nutritious parts of a plant's foliage are found at the very top, in the growing tips. 8

However, there is no reason to think that success in foraging and success in sex are mutually exclusive in their possible evolutionary influence. This perspective is yet another example of how these lanky, long-legged, long-necked giants embody the diversity of life carved out by evolution. At the same time, it can be difficult to imagine a creature as incredible as a giraffe having sex at all, let alone that they were shaped by it. But the same is true for thinking about sex between our parents, and yet the fact that we are here suggests that they - like giraffes - did it at least sometimes.

6. Simmons, R.E. & Scheepers, L. Winning by a neck: Sexual selection in the evolution of giraffe. American Naturalist 148, 771-786 (1996).
7. Mitchell, G., Van Sittert, S.J., & Skinner, J.D. Sexual selection is not the origin of long necks in giraffes. Journal of Zoology 278, 281-286 (2009).
8. Cameron, E.Z. & du Toit, J.T. Winning by a neck: Tall giraffes avoid competing with shorter browsers. The American Naturalist 169, 130-135 (2007).
9. Simmons, R.E. & Altwegg, R. Mating necks or competing animals? Criticism of ideas on the evolution of giraffe (Necks‐for‐sex or competing browsers? A critique of ideas on the evolution of giraffe). Journal of Zoology 282, 6-12 (2010).

Author: David P. Barash is an evolutionary biologist and professor of psychology at the University of Washington. His most recent book is called Buddhist Biology: Ancient Eastern Wisdom Meets Modern Western Science.
Original: Nautilus.

Biologists are still testing different hypotheses to explain the length of giraffes' necks.

The giraffe neck has intrigued people for a long time. One of the most famous explanations for why giraffes have a long neck was proposed by the outstanding French naturalist and naturalist Jean-Baptiste Lamarck - in his opinion, their necks were stretched from constant efforts to reach the leaves in the treetops.

Charles Darwin and Alfred Russell Wallace, the founders of evolutionary theory, agreed that it was all about tree leaves, but the personal efforts of giraffes had nothing to do with it. In each generation of animals, due to natural variability, individuals with longer or shorter necks appear, and those with longer necks gain an advantage - they feed better, reaching more leafy branches, and therefore feel better and reproduce better, passing on to the next generation are those variants of “neck” genes, with the help of which the neck becomes longer. This is one of the most famous examples of how natural selection works, and in this form - along with tall trees - giraffes found their way into all textbooks.

But is it only the inaccessible leaves that are the reason? In 1949, Chapman Pincher, a journalist and writer with a passion for zoology and genetics, tried to connect, so to speak, the long necks of giraffes with their long legs. It is quite obvious that it is easier to run away from predators with long legs, but as Pincher suggested, with such legs it is difficult to drink if there is water under your feet (and in nature, no one will bring water to the giraffes’ mouth). This hypothesis gained some popularity, but over time, paleontologists found fossil ancestors of modern giraffes that had long legs and a short neck and that for millions of years did not experience any problems with water.

According to another version, a long neck was primarily needed by male giraffes - a male with a longer neck could more easily defeat his opponent in a fight for a female, or females simply for some reason preferred longer-necked males. In other words, the length of the neck of giraffes was a trait on which sexual selection acted (we will not talk about the features of sexual selection, but we will recommend an excellent article on this subject by Boris Zhukov in Science and Life).

Finally, some experts believe that a long neck protects against overheating. It is known that temperature balance depends on the ratio of the surface of the body to its volume. The larger the surface, the faster the heat leaves; the larger the volume of the body, the more heat is retained in it. For a large animal living in a hot climate, it is important to get rid of excess heat to avoid overheating. It can be assumed that the long neck together with the long legs of giraffes increase the surface area of ​​the body relative to the volume, helping them cool. But in order to understand whether this is true or not, you need to accurately measure the giraffe’s surface and giraffe’s volume.

This is exactly what researchers from the University of Pretoria did with several giraffes from Zimbabwe. In an article in Journal of Arid Environments it is said that the body surface of giraffes is, on average, no larger than that of other animals with a similar body mass, so the “fridge neck” hypothesis will apparently have to be discarded.

However, the authors of the work describe another trick that can save giraffes from overheating: by standing with their heads directly towards the sun, they reduce the area of ​​​​the body illuminated by its rays - the sun simply does not hit the neck. Giraffes indeed often stand this way, but they probably had to look for a less “hot” position after they developed a long neck.