Feature

  1. Life

    Twin Fates

    Animal and human studies suggest that a girl with a twin brother may never completely escape the influence of her opposite-sex womb-mate.

    By Deborah Blum

  2. Out of Thin Air

    Biologists dream of the day when they could engineer crops to make fertilizer out of the nitrogen in the air.

    By Susan Milius

  3. All in the Family

    Contrary to popular belief, species of salamanders, birds, beetles and fish prefer to mate with close kin.

    By Ewen Callaway
  4. Health & Medicine

    You, in a Dish

    Human cells grown in conditions that mimic life inside the body are beginning to replace lab animals for testing drug candidates and industrial chemicals.