A twin study was undertaken with the twofold aim (a) of studying the hereditary behaviour of digital dermatoglyphic traits both at the qualitative and quantitative level, and (b) of working out a method for discriminating MZ and DZ twins by means of fingerprints.
Fingerprints of 50 MZ (25 ♂ and 25 ♀) and 50 DZ (25 ♂ and 25 ♀) twin pairs were thus examined and analyzed by means of a special methodology and of a 7044/K32 IBM computer.
The qualitative analysis has shown a significantly higher concordance in MZ than in DZ twin pairs, with a certain variability of single finger concordance values. The quantitative analysis has shown significantly higher correlation values in MZ than in DZ twin pairs, with very limited confidence intervals in the former. Single ridge counts apparently behave as cumulative counts on the five or ten fingers, although with an obviously higher random variability.
Digital dermatoglyphics thus appear to show practically complete genetic conditioning, which, rather than at a cumulative level for the ten fingers, as is largely believed, appears to act on single finger quali-quantitative traits. The total finger ridge count, rather than a trait, only appears to be a useful, but artificial cumulative value. Actually, applied to the diagnosis of zygosity, it provides, by itself, a fairly high, general probability (0.86) of a correct diagnosis.