«Lorsque certaines causes produisent certains effets, les eÂleÂments de symeÂtrie des causes doivent se retrouver dans les effets produits. Lorsque certains effets reÂveÁlent une certaine dissymeÂtrie, cette dissymeÂtrie doit se retrouver dans les causes qui lui ont donne naissance. La reÂciproque de ces deux propositions n’est pas vraie ...» . Pierre Curie (1908)

 

The issue of symmetry and deviation from it (asymmetry, laterality) in the natural sciences is known as an interdisciplinary field of knowledge and at the same time as an independent research tool. The concepts of symmetry and asymmetry appear in most sections of biology and medicine, especially where paired formations are present (neurology, orthopedics, nephrology, and others), are studied at different levels of organization (from molecular to population), and by different methods (physiological, morphological, biochemical, etc.), and are especially important in taxonomy and embryological studies. Comparison of the right and left sides, the influence of one lateralized factor on another, the search for causes, mechanisms, evolutionary advantages of laterality, the distinction between individual and population asymmetry, calculation of the lateralization index - all this has long become routine in some branches of science and at the same time is very poorly studied in others.

 

In the history of the study of asymmetry, there were ups and downs, there was a Nobel Prize (R.W. Sperry, "for his discoveries concerning the functional specialization of the cerebral hemispheres", 1981) and there was also an Ignobel Prize (R. Mieusset, e.a. "for measuring scrotal temperature asymmetry in naked and clothed postmen in France", 2019). The latter assessment is more typical - it is difficult for the general public to understand the practical benefit of comparing the right and left antlers of a deer or studying the direction of a snail coiling. But the modern routine planning of neurosurgical operations, which considers the lateralization of the language center, arose based on such "pure research".

 

The biological sense of the formation of front-back and upper-lower axes for animals moving horizontally under gravity is quite clear; it follows from a quote by P. Curie, the founder of this field of knowledge. A huge group of living creatures was named "Bilateria" precisely based on the shape of the body in terms of the doctrine of symmetry. Given the right-left symmetry of the environment (although this is sometimes questioned), we can consider biological laterality to be a deviation from the “Curie principle”. Behind every fact of inconsistency between the right and left sides lies a secret, and at the moment only a part of them has been revealed. Finding unexpected lateralization in any field of biology and medicine can be a trigger for new research and discoveries.

 

Small fluctuating asymmetries simply indicate instability or "noise" of development. Individual asymmetries with an equal number of right- and left-lateralized individuals (antisymmetry) can no longer be called accidental - there is already a factor that specifically breaks the symmetry. But the most interesting is directional (population) asymmetries, which suggest the presence of a factor of a certain direction, which breaks the symmetry of a bilateral organism, creating a preference for the right or left side. It is this group of asymmetries, asymmetry at the population level, including the study of its mechanisms and evolutionary significance, that is the subject of this project.

 

Numerous literature reviews summarize knowledge, but only on certain biological asymmetries. Some books try to cover all uses of the word "symmetry" together, including crystallography and physics, but they are popular science. The question arose - how do we unite in one project "under one roof" in different fields with different levels of sophistication and detail and, as a result, with different numbers of publications? How can to make disparate knowledge about asymmetry available for viewing, with the possibility of comparing them with each other to find new patterns and ideas for new scientific works? And how not to lose the scientific approach? This is how this project arose, which is, in fact, a synthesis of a scientific review and Wikipedia.

 

The information content of the project is based on scientific publications, which are presented in the form of annotations of several sentences, where the most important results and conclusions are described. You can always get more information if you find a work in well-known databases - for this, the bibliographic data of the publication (author's last name, title, etc.) are given. In addition, each work here is not only shortened but also somewhat simplified, so that it can be understood not only by a specialist in this narrow issue but also by every person with a medical or biological education.

 

As of the beginning of 2024, the author has completed an analysis of scientific works found in the "Scholar Google" system for such words in the title as asymmetry, asymmetries, unilateral, and laterality for all years (46,000, 18,000, 50,000, and 6,300 sources, respectively). The total revision made it possible to find many interesting works that were threatened with oblivion. These works make up the vast majority of here, although some publications were found by reference lists and other keywords.

 

In the process of working on the project, the author had to quickly abandon the original plan - to collect absolutely all work on the topic of directional asymmetry. They turned out to be more than expected, and the excessive number of included publications can "clutter" the project. Therefore, such a gradation was developed: if there are very few works on a certain topic, then all are included, no matter how "weak" they seem. If the number of works is dozens and hundreds, then the most important and high-quality of them are placed, and if there are thousands of them, then it is worth putting reviews and meta-analyses with generalizing conclusions in the first place (and adding to them only individual publications that go beyond the limits and ask new questions). At the same time, the author understands how subjective the impression of "weak" or "quality" works can be, and how incorrect the prevailing opinion can be. However, the collective nature of this project should remedy the situation.

 

A separate issue is the cataloging of scientific works. On the one hand, here you will return to good old library catalogs (only not in wooden boxes, who still found them), with sections and subsections. Modern title keyword searches are imperfect. For example, the work may present an evolutionary approach to solving a certain question, but the word "evolution" will never appear in the text. In the process of working on the project, I managed to find many interesting works without the words "asymmetry" or "laterality" or their derivatives. On the other hand, cataloging with modern methods can be carried out in several dimensions, achieving a selection from a huge mass of publications only those that interest you, with the possibility of broad comparisons between neighboring topics.

 

A project of this nature seems to be long overdue. For example, back in 2011, in the materials of the symposium "Evolution of Chirality" during the European Congress of Evolutionary Biology (ESEB), it was written as follows: «Left-right asymmetry patterns in the body shapes of animals and plants have been a continuous source of interest among biologists. Recently, inroads have been made to developing a coherent research programme that makes use of the unique fact that chiral patterns may be studied (and generalities deduced) by comparisons across many unrelated groups, even across Kingdoms.» (SCHILTHUIZEN, M. E. e.a. Left-right asymmetry in plants and animals: a gold mine for research. Contributions to Zoology, 2012, 81.2: 75-78).

 

And, as it seems to the author, similarly there was a need to create a scientific review of a new level. An online portal dedicated to a specific scientific topic, with a faster exchange of opinions than comments in scientific journals and responses to them. Collective work, that is scientific crowdsourcing. Search, selection, processing, standardization, and manual cataloging of scientific works (by content, not by keywords). Simplification and shortening of publications for faster and easier understanding. Timely replenishment with new data. Project moderation and development. Search for consensus on debatable issues (here - under development).

 

Only time will tell how much a project based on such principles will become necessary and popular.