Biometry (Anthropometry)

BIOMETRY (ANTHROPOMETRY). - I. ORIGINI E DEFINIZIONE. - Biometrics was born at the historical moment when, in the life sciences in general, the qualitative method was beginning to be replaced by the quantitative one, that is, when there was a tendency to make measurable the concepts of large or small, long or tall, light or heavy, dense or fluid. This was in fact the direction that arose at the end of the 16th century and then, still more, in the 17th, with the great works of Descartes and Bacon of Verulam, if one does not wish to cite Galileo himself as the true founder of the new method of scientific investigation. In this atmosphere, the quantitative method came to be introduced also into the systematic study of living beings. Santorio Santorio of Capodistria (1561-1636) is perhaps the initiator of such research and the founder of a veritable school that had a vast repercussion throughout the medicine of the era, especially in England (with the so-called iatromathematics). Thus people began to measure the most diverse functions and the most diverse characteristics of the human organism, healthy and diseased, while there were introduced the concepts of the normal (average) intensity of each biological fact studied, and those of variability and of the reciprocal connection among them. In time the methods of metric assessment also became simplified, whereas, for example, Santorio had counted pulse rates with a special pendulum borrowed from the work of his colleague Galileo. And mention should be made in this connection of the English physician John Floyer (1649-1734) with his two volumes of Symptomatic Therapy: for the purposes of method his contribution is still interesting, since he constructed an apparatus for measuring pulse rate.

In other respects one should recall many names of authors who, through their works, made it possible to give biometrics individuality as a science. Captain John Graunt (1620-74) formulated the first biological interpretations of the principal demographic phenomena, thus giving life to a new chapter of the science that measures births and deaths and detects the laws of natural development of populations. To the Belgian Adolphe Quetelet (1796-1874), on the other hand, belongs the merit of having founded modern anthropometry. Yet the development of research was slow, and the truly new contributions are owed to the Moravian monk Gregor Mendel (1822-84) and to the Englishman Francis Galton (1822-1911), founder of the English biometric school and of the famous journal Biometrika, later directed by K. Pearson and still published today.

From these precedents the method of quantitative assessment has extended ever more greatly to the solution of the most disparate biological problems, so that today one speaks of a biometrics, as a science, distinguishable into human biometrics (anthropometry), animal biometrics and plant biometrics. However, some authors propose other subdivisions which, though, are either merely formal or are based on the technique followed in the assessment and elaboration of the data. In a scientific setting, a general definition of biometrics could be formulated as that «discipline which investigates statistically the state, the consistency, the natural and social movement of populations, and the forms, functions and psychology of living organisms». Thus organisms are considered not only insofar as they form populations but also from the point of view of their individual characteristics. The conception is in reality extremely vast, and therefore a limitation of the subject matter has been attempted several times, but this is erroneous if it must lead to an arbitrary fragmentation of research, similar to what happens in biology. Indeed, in the sense set forth, biometrics turns out to be biology itself treated according to the principles of modern statistics; the distinction is therefore founded solely on the technical direction of assessment and elaboration of the data, not on the nature of the problems to be studied, which are always biological. For this reason it would perhaps be desirable that, at least in the theoretical sphere, if not in the didactic one, the distinction of biometrics with respect to biology be abolished. The question is only apparently formal, but in practice the errors scattered throughout the literature are explained by the fact that biometric research has often been carried out without an adequate preparation on the biological problem, or conversely without a sufficient knowledge of statistical technique, of its possibilities and its dangers.

This being stated, biometrics must be considered a true science and therefore must tend not only to the search for truth, but for truth in the laws of nature. Too often metric assessments have been carried out without any precise biological objective to be attained: this means when they have been justified only by the empirical observation of recording a measurement or an angle, etc., in order to study, for example, racial or group differences. But once the differences are found (we shall always find them within the domain of life!), the rest has been neglected or entrusted to some intuitive interpretation or other. And this is not the result of such an investigation. If anything, the intuitive interpretation could most often be formulated a priori, before the measurements, before any mass observation. From the investigation, then, there remain only simple differences, not constant or normal relationships, and still less biological laws, toward which on the contrary biometrics can and must tend and which, thus conceived, takes on a character proper to an experimental science. Its quantitative method must be considered in this way as a precious working tool, not as an objective of investigation on the part of the biologist. Moreover, it should be noted that the development of research requires neither higher mathematics nor an excessive abstraction from the practical biological problem, but rather a forma mentis suited to quantitative judgment, even of facts observed qualitatively and merely catalogued. This has been demonstrated above all by research on the morphological variability of the human brain and, within the sphere of psychology, by the elaboration of the results obtained from mental tests.

II. MAIN RESULTS

If one were to attempt an organic and summarizing treatment of the whole of b., it would appear disjointed in its parts, perhaps disharmonious, with numerous discontinuities, precisely because of the aforementioned failure to incorporate it into biology, of which it is an integral part as a science (if not for its technique). But it is a disharmony that is only apparent, which would lead us along the road already traveled by biologists in the various specialized fields, with the rigorous method of work and interpretation that comes to us from the mathematical and statistical sciences, from the examination and investigation of the laws of growth of cells and tissues, to the biological interpretation of the natural movement of populations, to the examination of biocentric equilibria, to demogenetics, to the study of the variability of human, animal and plant characters, to the problems of sex from the biometric point of view, to the practical study of yields in the zootechnical and phytotechnical fields. The principal results obtained so far have shown that at the present moment we should above all abandon the old procedure by which, having formulated a more or less vague theory, one went looking for all possible confirmations of it in every field. We should rather dedicate ourselves to the direct solution of the many biological problems that present themselves to us every day, at the purest source of observation and experience, giving up "the sublime pretensions of origins and principles, from which the whole science of nature was to be deduced" (from the inaugural address of Salvatore Tommasi for the year 1866 at the University of Naples).

Schematically, the essential chapters of b. (especially of human b.) treat the following subjects:

1. Evolution and selection of groups (laws of development, natality, mortality, historical theories on the doctrine of species, etc.);

2. Genetics (phenogenetics, hybridisms, multiple factors, norm of reaction, human eugenics, etc.);

3. Demogenetics (which studies the nature of the similarities and dissimilarities among groups or natural complexes of organisms and their respective descents, according to A. Sacchetti, judging the heredity of characters in conformity with the different systematic hierarchy of the group under examination);

4. Growth, mean and variability of characters (where morphological, physiological and psychological characters of all categories of individuals are included, for which there have arisen, for example, a comparative criminology, a psychometry of the deceased, and so on);

5. Practical classification of races (for which the biometric and demogenetic method is extensively used);

6. Constitutions (within the sphere of so-called biotypology, according to Pende, which treats many problems from the anthropometric point of view, such as the equilibrium of circulating hormones, the morphological classification of types, the correlation among individual characters, etc.).

Alfredo Sacchetti