People living in remote villages in Ecuador have a mutation that some biologists say may throw light on human longevity and ways to increase it. The villagers are very small, generally less than three and a half feet tall, and have a rare condition known as Laron syndrome or Laron-type dwarfism. They are probably the descendants of conversos, Sephardic Jews from Spain and Portugal who were forced to convert to Christianity in the 1490s but were nonetheless persecuted in the Inquisition. They are also almost completely free of two age-related diseases, cancer and diabetes. A group of 99 villagers with...