Passage 1

Lonely people, it seems, are at greater risk than the gregarious of developing illnessesassociated with chronic inflammation, such as heart disease and certain cancers. A paper publishedlast year in the Public Library of Science, Medicine, shows the effect on mortality of loneliness iscomparable with that of smoking and drinking after examining the results of 148 previous studiesand controlled for factors such as age and pre-existing illness.

Steven Cole of the University of California, Los Angeles, thinks he may know why this is so.

He told the American Association for the Advancement of Science meeting in Washington, D.C.,about his work studying the expression of genes in lonely people. Dr. Cole harvested samples ofwhite blood cells from both lonely and gregarious people. He then analysed the activity of theirgenes, as measured by the production of a substance called messenger RNA. This molecule carriesinstructions from the genes telling a cell which proteins to make. The level of messenger RNA frommost genes was the same in both types of people. There were several dozen genes, however, thatwere less active in the lonely, and several dozen others that were more active. Moreover, both theless active and the more active gene types came from a small number of functional groups.

Broadly speaking, the genes less active in the lonely were those involved in staving off viralinfections. Those that were more active were involved in protecting against bacteria. Dr. Colesuspects this could help explain not only why the lonely are iller, but how, in evolutionary terms, thisodd state of affairs has come about.

The crucial bit of the puzzle is that viruses have to be caught from another infected individualand they are usually species-specific. Bacteria, in contrast, often just lurk in the environment, andmay thrive on many hosts. The gregarious are therefore at greater risk than the lonely of catchingviruses, and Dr. Cole thus suggests that past evolution has created a mechanism which causes whitecells to respond appropriately. Conversely, the lonely are better off ramping up their protection

against bacterial infection, which is a bigger relative risk to them.

What Dr. Cole seems to have revealed, then, is a mechanism by which social environmentreaches inside a person′ s body and tweaks its genome so that it responds appropriately. It is not thatthe lonely and the gregarious are genetically different from each other. Rather, their genes areregulated differently, according to how sociable an individual is. Dr. Cole thinks this regulation ispart of a wider mechanism that tunes individuals to the circumstances they find themselves in.

What can we know about viruses and bacteria from the fourth paragraph

• A.Viruses often remain hidden in the environment
• B.Bacteria are passed to other people by the infected individual
• C.The lonely people can catch viruses more easily
• D.Viruses pose a greater threat to the gregarious than bacteria