American neurosurgeons have found signs in the human skull that fit into the golden ratio. This is an arc from the bridge of the nose to the end of the occiput, on it is the point of intersection of the two parietal sutures, which divides the arc into two unequal parts. Researchers studied the skulls of six other mammals, but none of them found such a relationship between these points: the skull of the American rabbit was the farthest from the presence of the golden ratio, the lion was closest, scientists write in the Journal of Craniofacial Surgery.
Among biological objects, the golden ratio is best studied in plants: it is known that this principle often obeys the spiral arrangement of leaves or petals in flowers. But in animals and in humans, it has also been repeatedly found. For example, in the ratio of the size of the left ventricle of the heart and its inlet or in the parameters of the shape of erythrocytes.
Rafael Tamargo and Jonathan A. Pindrik of Johns Hopkins Hospital studied the size of a human skull. In the course of evolution, the hemispheres of the brain in humans have greatly increased, and scientists wondered if there was any optimal relationship between the measurements of the brain. And since the size of the brain is closely related to the size of the surrounding bones, they measured the skull itself.
The scientists worked with MRI scans that patients at Johns Hopkins received to confirm their diagnosis. The researchers selected 100 scans of people aged 18-97. They verified that the patients did not have severe diagnoses that could significantly affect the shape of the skull and the size of the brain, such as hydrocephalus, malformations or growth abnormalities. Indications for MRI in all patients were not related to the morphology of the skull: they were trauma, convulsions, loss of consciousness, or mental illness.
On all scans, the researchers measured the length of the nasioinial arch: it starts from the nasion - the point at which the border of the nasal and frontal bones intersects with the axis of bilateral symmetry of the skull - and ends at the inion, the most prominent part of the occipital protuberance.
In addition, they measured the distance from the ends of the arc to two intermediate points that lie on it. The first - bregma, is located at the point of convergence of the coronal (lateral) sutures of the skull with the sagittal (central). The second is the lambda, located closer to the back of the head, where the sagittal suture intersects with the sagittal (posterior) suture.
The location of the points on the skull and the relationship between the arcs that connect them.
Scientists found that the ratio of the arc as a whole to its back (from bregma to inion) is 1.64 ± 0.04. The rear to front ratio (from bregma to nose bridge) is 1.57 ± 0.10, which is close to the Φ number in the golden ratio, which is approximately 1.618. The segments separated by the lambda did not form such a relationship.
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The researchers also measured the skulls of six different mammalian species: tiger, lion, rhesus monkey, blue monkey, domestic dog, and American rabbit. However, they did not find similar relationships in any of the animals. The rabbit skull was farthest from the golden ratio, the lion came closest to it. In all these animals, the arc from bregma to iniona was less pronounced, therefore the ratio of the entire nasioinial arc to this segment was greater.
The ratio of the length of the arches in different animals. NI - nasioinial, BI - bregmoinial, NB - nasiobregmal.
Thus, scientists have found that the ratio of brain sizes in humans is close to the golden ratio, unlike other mammals. It goes without saying that the brain seeks to achieve these parameters, and that some animals have advanced in this direction further than others. Nevertheless, the authors of the work draw attention to the fact that in living nature the presence of the golden ratio indicates a balance between the form and function of the organ. Therefore, it cannot be ruled out that this is the shape of the brain that turned out to be optimal for a person during the growth and development of the cerebral hemispheres.
Polina Loseva