Gemelology

Hemelology is a branch of zoology that studies twins in animals and humans.

Twins can be either identical or fraternal.

Identical twins share the common origin of a single fertilized egg that then splits into two. Such twins are always of the same sex and, as a rule, are very similar to each other.

Fraternal twins come from two different eggs that are fertilized by different sperm. They can be the same or different sexes and do not always look alike, despite the fact that they share a common set of genes.

Twins often have common diseases, and this is due to the fact that they have the same set of genes, as well as living and nutritional conditions. For example, if one twin has a pollen allergy, the other may have the same allergy.

Gemellology studies not only twins, but also other pairs of organisms that share common features, such as conjoined twins or clones. These pairs can be created artificially, for example, by cloning.

In general, gemellology is an important branch of zoology and can help in understanding the development of an organism and its adaptation to the environment.

Gemelology, or hemellologia (Greek ἡμίολόγος “shepherd; able to explain”, Latin Gemellology) is the study of pairing and symmetry, in particular, symmetry in nature, architecture and abstract ideas. Its subject is the properties of figures that have a geometric structure. According to R. Cowell's definition, this is a system of knowledge about equality, similarity and the product of twice the whole. The essence of hemillology can be formulated in the phrase: “What is paired is unlike what is not paired.” .

Gemellogical concepts are mentioned by Aristotle in his treatise “Categories”, they were studied by Gerres, and the doctrine of symmetry was expounded in the most detailed way by Aristotle in “Physics”. After the Copernican revolution in astronomy, Agrippa, Dante, Ptolemy and Pliny the Elder discussed directions in the celestial sphere. The polymath Varario wrote about this branch of geometry, but since he deals only with even figures, his cycle has few points of contact with “ordinary” gemellology. The works of Heron of Alexandria were long considered lost until they were discovered in the library of the city of Beon by Joseph Blackwood and published in 1719. In his work “Analysis of the rules of geometry, according to which the same figure has several forms,” Blackwood refutes the views of Aristotle and Porphyry on the theory of symmetry: the principle of similarity, which he did not introduce into geometry, unites the quadrangle and the pentagon and the triangle; all conical and congruent bodies have circles of the same radius and all hexagons belong to infinite figurative series with indefinite completeness, the so-called “Harry figures”.