One to 64,000,000,000
Finger-prints, so important to police in the detection of crime and to bureaucrats in the control of those who would evade bureaucracy, have been utilized now for just over half a century.
Our finger-tips are constantly and involuntarily making these prints because of the tiny sweat-pores on the patterned ridges. Indeed, a magnifying glass of ten magnifications will just reveal what the plant anatomist and microscopist Nehemiah Grew (1641-1712) was probably the first to notice - that 'every Pore looks like a little Fountain, and the sweat may be seen to stand therein, as clear as rock water, and as often as it is wiped off, to spring up within them again'.
But Grew did not observe what is now a commonplace, that 'in each individual' (to quote the current edition of Gray's Anatomy), 'the lines on the tips of the fingers form distinct patterns unlike those of any other person'. This uniqueness of a man's finger patterns, and so of his prints, may have been known to the Chinese. The evidence is not conclusive, though from an early period they were well acquainted with finger-patterns and frequently signed contracts and documents with an inked impression of the finger-tip.
In the West, two men, independently of each other and of any Eastern knowledge, realized that finger patterns could be a means of identification. These were Sir William Herschel (1833--1917) and Henry Faulds (1843-1930). Herschel, when he was a civil servant in India, began to take what he called 'sign-manuals' of contractors, pensioners and convicts. The first palm-prints and finger-prints he recorded, with oil-ink, in 1858, were those of a Bengali village contractor. Herschel discovered that finger-tip designs do not change in a lifetime. As early as 1877 he attempted to have a system of recording prints accepted in Bengal, as a deterrent to tricksters and as a means of identifying criminals.
Faulds was a medical missionary in Japan. In 1878 or thereabouts finger-prints on some ancient Japanese pottery suggested to him that 'bloody finger-marks', as he wrote in a letter to Nature in 1880, might lead to the 'scientific identification of criminals'. Faulds had once worked with a firm of shawl manufacturers arranging, classifying and numbering an immense variety of patterns. The whorl-patterns of Paisley shawls helped to sharpen his eyes to the not dissimilar whorls on the human finger.
Some months before his letter appeared in Nature, Faulds had written to Darwin about finger-patterns; Darwin handed his letter to Francis Galton, who was then working on the laws of heredity. Galton must also have read the letter in Nature and the letter which it elicited in turn from Herschel. It was Galton who established the uniqueness of the individual's ridge patterns, and made suggestions for a workable police system. In Finger Prints (1892) he calculated the chances of duplication. The improbability of one finger-pattern in one individual coinciding with one finger-pattern in another individual he found to be 1 to 236, or 1 to about sixty-four thousand millions: 'When two fingers of each of the two persons are compared and found to have the same minutiae, the improbability of 1 to 236 becomes squared, and reaches a figure altogether beyond the range of imagination; when three fingers, it is cubed, and so on.'
Finger-printing was quickly adopted, first of all by the Argentine in 1891. In 1892 the La Plata police caught a murderess by means of her prints. Scotland Yard took to finger-printing in 1901, abandoning the cumbrous and less certain anthropometric system of Alphonse Bertillon, chief of the Paris Police Identification Service, who followed the principle of the great Belgian statistician, L. A. J. Quetelet, that the measurements of no two persons are alike. This system required careful measurements of parts of the head, fingers and limbs. It was far from foolproof. In America, in 1901, a convict named West, arriving at jail at Leavenworth, Kansas, denied having been there before. After some enquiry he was confronted by another man astonishingly like himself. His Bertillon measurements were similar - and his name was also West! But the finger-prints of the two men were different.