WITH the construction of the railways in the 19th century, a new sociological phenomenon was born: the travelling criminal. Until then, police had relied on local communities to recognise a bad apple in their midst, but now the felons were on the move, wreaking havoc in communities which had no knowledge of their past and hence no reason to be wary. For law enforcers trying to contain the problem by sharing descriptions of known recidivists, it became imperative to answer one question: what is it that identifies someone as a particular person?
This question has long troubled humanity, of course, and it is explored in all its facets in a new exhibition at the Wellcome Collection in London. One practical application lies in the forensic arena. The first solution offered, branding, was simple and effective. But even in a society that preferred to believe that criminals were born and not made, this was soon deemed unacceptable. So there was a need to find something innate to human beings that remains constant from the cradle to the grave, and that is sufficiently differentiated in the population to make it useful in identifying individuals.