Embryonic Fingerprint Formation

The study and classification of fingerprint patterns—dermatoglyphics—has a long history and their widespread use in genetic, clinical, pathological, embryonic, anthropological and forensic studies (not to mention palmistry) has produced an extensive descriptive literature. Figure 6.20(a) (see also Figure 12.5(c)) is a photograph of a human fingerprint on which various common traits are marked. The descriptive methods used may loosely be described as topological, that is, those associated with the study of properties that are unchanged by continuous deformation (Penrose 1979), and statistical (Sparrow and Sparrow 1985) and depend on the area of application. Topological methods have been found to be especially efficient for genetic and diagnostic purposes because ridges appear in their definitive forms during embryogenesis and the basic patterns do not change under continuous deformation during growth (Elsdale and Wasoff 1976, Loesch 1983, Bard 1990).3

In a study of two-dimensional patterns created on a confluent dish of normal fi-broblasts, and dermatoglyphic patterns of primate palms and soles, Elsdale and Wasoff (1976) observed that both patterns were characterized by different types of interruptions or discontinuities in fields of otherwise parallel aligned elements. They concluded that because the discontinuities were invariant under plastic deformations as well as rigid motions, topological considerations in addition to analyses of cell behaviour were necessary to understand dermatoglyphic pattern development. However, topological clas-

3The old literature abounds with interesting studies. In one 19th century book the author describes in great detail the effect on his fingerprints of self-mutilation. When he had used up all his fingers he moved on to his feet. The results of 40 years of this were completely inconclusive but he had a lot of interesting scars.

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