Returning to classical times, but now to genealogies of the Turko-Mongol rulers of 500 years ago, many pedigrees include the opposite convention-so that circles denote males and squares denote females ( fig 5). If square and circle are now taken for granted, the origin of even such an established convention may be open to debate. This was not only for reasons of simplicity and space, but also for other reasons, such as the greater ease of representing affected, unaffected, and carrier individuals. 1 Nevertheless, although the classical symbols are rarely still to be seen, 7 the square and circle came to dominate illustrations of the pedigree. Applying the convention whereby roman numerals ordered vertically downwards delineate successive generations, and arabic numerals sequenced rightwards delineate individuals, famous members of this family can be pinpointed and include the pottery designer and manufacturer Josiah Wedgwood (I-1) the eminent physician Erasmus Darwin (I-4) the evolutionary biologist and naturalist Charles Darwin (III-3) and the eugenicist and pioneer of heredity Francis Galton (III-9).ДЄt the beginning of the 20th century, rather quaint depictions of pedigrees and symbols were occasionally to be found, and texts sometimes showed examples using both styles of pedigree. 6 Also, this pedigree illustrates a remarkable dynasty. It not only shows the early use of the American symbols in England, but also has deliberately been manipulated for a variety of political and social purposes by the eugenicists of the day. The pedigree in figure 4 provides a striking example of the use of the square and circle. Thus many British geneticists, a number of whom were also eugenicists, favoured the classical symbols, whereas the Americans favoured the modern ones-on the valid grounds that the modern symbols were easier to read and took up less space. Nettleship conceded that вЂњthis fragment of history does not affect the merits of the question at issue in its practical aspect, and it could not be quoted as in any way weakening the position of those who favour the retention of the classical biological symbols.вЂќ 5 His comment, epitomising the difference in opinion on the merits of using the classical symbols versus the square and circle, mainly reflected the different national preferences. Nettleship, who did not approve of the use of squares and circles, explained that at the time Earle was вЂњunable to get any printer's symbols capable of use for his purpose except those employed in printing music.вЂќ 5 Indeed, careful inspection of figure 3 shows the circles have the slightly elliptical shape of musical notes, in keeping with Nettleship's observation that the affected and unaffected female symbols resembled respectively crotchets and oval semibreves (or, perhaps more convincingly, minims). 3Д¬ontemporary male and female symbols were first used in this pedigree of colour blindness in 1845 4ДЄlthough Earle does not report why he used these symbols, a contemporary account refers to Edward Nettleship, fellow of the Royal Society and consultant ophthalmic surgeon to the Royal London Ophthalmic and St Thomas's Hospitals, who provides the probable answer. These derivations have been traced by Renkama, who illustrated how Greek letters can be transformed into the graphic male and female symbols still recognised today ( fig 2). What of the graphic symbols themselves? The most established view is that they are derived from contractions in Greek script of the Greek names of these planets, namely Thouros (Mars) and Phosphoros (Venus). Metaphorically, in comparison with the sun and the purest metal gold, iron was baser, harder, and associated with Mars and the masculine copper, which was also base, was softer and associated with Phosphoros or Venus and the feminine.

Later, religious rites that revolved around the seasons and were practised by many crafts (but particularly those involving metal-work) formed the links between the gods, astronomical signs, and metals. These heavenly bodies had become associated with the names of gods, a concept the ancient Greeks acquired from the Babylonians. Filled symbols denote clinically affected individuals with facio-scapulo-humeral muscular dystrophy 10ДЇor the ancients, movements of the heavenly bodies seemed to influence the seasons and thus the cycles of growth of plants and of breeding of animals. One version of the classical male and female symbols on a pedigree.

Ancient symbol for female divinity