People leave molecular wakes that may give away their secrets

GENES CANDNADNA tell tales about you, from who your ancestors were to how likely you are to develop a range of diseases. And it seems probable that in the future they will tell more: your personality type, perhaps, or your intelligence. For these reasons, many countries have laws limiting what use employers and insurance companies can make of such information. America, for example, has the Genetic Information Nondiscrimination Act, which makes it illegal for health insurers and employers to use genetic information to discriminate against customers and employees.There is much, however, that genes cannot reveal. They are blind to what you eat, how you exercise, how safe the place you live in is, how you unwind at the end of the day and which god you worship. Just as well, you might think, considering how easy it is to obtain samples of from saliva, sweat or hair, and how cheap it is becoming to analyse such samples. But it is not just that people scatter to the wind as they go about their business. They shed a whole range of other chemicals as well, in their breath, their urine, their faeces and their sweat. Collectively, and somewhat inaccurately, these molecules are referred to as metabolites. Some truly are the products of metabolic activity within people’s bodies. Others are substances an individual has come into contact with, or consumed or inhaled. All, though, carry information of one sort or another.