Nietzel says the most common place the clues about "where warm waters halt" first lead people is to Eagle Nest Lake, about 100 miles north of Santa Fe, because it has a dam that holds back warm water and is known for its brown trout.

NPR: 'I Love Mysteries,' Says Man Claiming Hidden Gold

For the more common "dry" form a series of genetic discoveries have offered the first good clues to its causes, providing leads for new drugs and genetic diagnostic tests.

FORBES: Banishing Blind Spots

With no environmental clues as to their common ancestry, the birds were nevertheless able to engage in full-fledged nepotism.

ECONOMIST: Team players