One's desire to be alone, biologists have found, is partially genetic and to some degree measurable. If you have low levels of the pituitary peptide oxytocin--sometimes called the master chemical of sociability-- and high quantities of the hormone vasopressin, which may suppress your need for affection, you tend to require fewer interpersonal relationships.
Michael Finkel, The Stranger in the Woods: The Extraordinary Story of the Last True Hermit
alone