Have you ever thought about why a person’s butt (professional name butt, commonly known as butt) grows into this shape? Looking around, why are only human butts "two pieces of flesh"?
is not wrong. Among all living things on earth, human butts are unique. Even human close relatives, such as chimpanzees, bonobos and gorilla , do not have human butts. Then why evolve like this?
Humans have a unique butt
"Hump" can be said to be a unique feature of most mammals. The "Hump" here specifically refers to hip bone and its attached muscles and fat. Like chickens, ducks, fish and birds, there is no real "buttocks". Early mammals, most amphibians, reptiles, birds and some fish, only have an organ like a "cloaca".
The hip structure consists of the gluteus muscles: gluteus melis, gluteus medius and gluteus maximus . For most mammals, the hip structure is mainly composed of the gluteus medius. The most important gluteus muscles in humans are the gluteus maximus, which is the main reason why humans have different hip structures from other animals.
. This is actually the by-product of human walking upright , and it is also one of the milestones in the history of human evolution.
Walking upright changed the human buttock structure
In fact, at the beginning, our ancestors initially walked with their limbs, and the requirements for leg muscles were higher. More muscles were used to serve the lower limbs and exert force, resulting in the muscles in the legs being more developed, followed by the buttocks.
About 6 million years ago, the first batch of human ancestors discovered the ability to stand upright (stand on two feet). This group of primates no longer use the forelimbs during movement and completely relies on the strength of the hind limbs to walk.
Our pelvis no longer needs to use arms to help walk upright, so that our hands can be freed. The result of this is that the human gluteus minimus no longer moves the thighs backwards at the hip joint like other ape . Instead, they cause the thighs to rotate outward from one side of the body. This new movement produced by the gluteus minimus is crucial to avoid falling while walking, but it reduces the number of muscles that can move the thigh backward, and moving the thigh backward is also an equally important movement to move the body forward while walking. This transformation means that all the forces required to move forward (such as walking) must be produced entirely by the gluteus muscles, which requires that our hip muscles be completely repositioned, and the gluteus maximus of the larger muscles come to the middle position, and the hips grow close to the upper part of the femur (thigh bone). It must compensate for the loss of the other two muscles that will produce the same effect, thus forming a unique hip structure.
The role of gluteus maximus and small gluteus muscles
gluteus maximus has another qualitative difference between other primate types of gluteus epithelial muscles: it not only "picks" a piece of flesh of the gluteus medius at the upper end, but successfully climbs to the waist, grasps the back end of the pelvic iliac , and leaves rough attachment marks there (posterior hip line). This gives the gluteus maximus a solid attachment when it contracts, thus bursting out with greater strength.
When our ancestors became completely bipedals, their pelvis had become short and wide. So the two smaller hip muscles, the gluteus medius and gluteus minimus, migrate to both sides of the body to help us stabilize the pelvis when we hit the ground with one leg and swing forward with the other leg.
The result is that When we stand on one leg, our small gluteus muscles (glutes medius and gluteus minimus) play a role to help the hip muscles not disperse to both sides. By changing the small gluteus muscles and their functions, the human hip bone curved structure can achieve single-leg standing.
To put it simply, the gluteus maximus shapes our hips and improves strength, while the small gluteus muscles provide stability.
So scientists have found that kinematics research has found that standing and walking slowly on both feet does not require strong gluteus maximus. Active exercises of the gluteus maximus require high stability of the hip and large stretching of the hip joint (both tiring). It not only includes squats, standing body forward flexion and other two-foot standing postures, but also a series of derivative exercises supported by one-foot: jumping, climbing stairs, running, etc. This is also the reason why most athletes have hip buckles.
In addition, the hips also form a layer of fat pad for "buffering", so that the gluteal muscles will not be damaged by rubbing the hip bones while walking or sitting, thus evolving and developing your current "butt".
The production of buttock fat has another layer of effect. The human brain is relatively large and consumes a lot of energy. Our body stores energy in the form of fat. For a non-aquatic breastfeeding organism, the proportion of fat in human body is relatively high. From this, anthropologists suggest that human body fat helps buffer our brains, which have high metabolism costs, through periods of nutritional deficiency. Even the thinnest people have more buttock fat than other mammals. Because we need more fat to maintain our enormous reproductive processes that consume huge energy and carry out energy reserves. Buttock structures such as
will also have bad
Of course, such buttock structures are a beneficial evolution for humans, but there will also be many inconveniences, such as cleaning the buttocks after convenience, and the occurrence of hemorrhoids.
Because of the unique buttock structure, the human anus is wrapped inside the buttocks. If it is not cleaned, the feces residue will remain there and a odor will be raised. In the primitive society, this is not conducive to primitive humans hunting. Think about it, primitive people were hunting, but animals smelled the odor several kilometers away. Will it not run?
also because of such a unique buttock structure, the buttocks of humans walking upright are pressed to the bottom of the torso. Various activity intensities change the tension and blood vessel distribution of the anus. When the anus is compressed by internal organs and gravity for a long time, the upward return of the veins during blood circulation will be blocked, which can easily lead to excessive veins.
In short, it is safe to say that the buttocks have a special status in human history, not only because the evolution of the buttocks is crucial to human survival, but also because it is an important symbol in the history of human evolution.
References:
, Daniel Kolitz. Why Do We Have Butts? Gizmodo.2018.5.14.
, Bret Contreras. The Evolution Of The Gluteus Maximus. The Glute Guy.2015.2.6.
, The evolutionary history of human obsession with the buttocks. Global Network. 2015.9.10.
4, Kenneth A. Johnson MVSc, PhD, FACVSc, in Piermattei's Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat (Fifth Edition), 2014.
5, Why Do We Have Butts?ByDaniel Kolitz PublishedMay 14, 2018 Comments (93)
