Floreana Island's postal service hasn't evolved from its origins hundreds of years ago. But unlike Darwin's finches, it doesn't need to adapt to survive.

Instead of stamps and postmen, the Galapagos isle relies on a barrel and the kindness of travelers to move its mail. Twice a day including Sunday, boatloads of unofficial mail carriers land in Post Office Bay and walk a few sandy yards to a wooden barrel crammed with postcards and notes left by past visitors. The guests, mainly cruisers eco-touring the Ecuadorian islands, sort through the stacks, looking for addresses within delivery distance of their homes. They also drop their own messages into the receptacle, adding another link to the chain of mail.

"Sometimes it's faster than the regular mail," said our guide, Carlos, as he yanked dozens of letters from a plastic bag. "You come one day and drop it off two days later."

The practice started in the late 1700s as a way for English whalers to communicate with friends and family back home. The men heading out to sea would deposit their correspondence, which sailors returning home would collect and deliver.

The "post office" looks like an installation piece by Robinson Crusoe, with artful piles of driftwood and other organic detritus surrounding the elevated barrel. Stickers, scrawlings and a poster of Golden Age Hollywood stars adorn the artifacts as if they were a bathroom wall in a bar.

Since this was our fourth day of traveling together, our group of 16 knew one another's home towns, and we hollered out international cities hoping to make a match. A New Yorker named Maura approached my parents with "Brookline," thinking that the Boston neighborhood might be close to their home in western Massachusetts. She kept one destined for Cambridge, Mass., planning to drop it off during an upcoming trip there. The Swedish family grabbed a Stockholm-or-bust postcard and gave me a patient grin when I asked whether a holiday in Copenhagen was in their future.

In my cluster, I found cards addressed to California, Toronto, France and Germany. One for Vancouver said, "We are stranded on Postcard Island. Send help. Quick. Stop." A sheet of thin, fraying paper covered in tiny print needed a lift to Romania. I was tempted to deliver it myself, worried that it might disintegrate before a Romanian-bound traveler could save it. After flipping through countless images of sea lions and blue-footed boobies, I finally scored: East Capitol Street, Washington, D.C.

It was exciting to make a connection, but then I realized that I actually had to deliver the postcard -- or else let down the writer as well as a centuries-old tradition. Buying a stamp and mailing it is considered cheating, Carlos warned us. But arriving at a stranger's house with a "surprise" from someone you've never met could be a little creepy, no?

To her credit, Kathy Brennan was a model recipient. I left a note in her mailbox saying that I wished to deliver a special something from her friend Nancy and asking her to call me to arrange a time. When we talked on the phone, she was excited to hear that I knew Nancy, until I admitted that I had no idea who Nancy was, but that I was her messenger. Even after that, she invited me over.

In her living room, I handed her the postcard of two frolicking sea lions, explaining its journey from a barrel in the sand to a rowhouse in Washington.

"I'm amazed that you picked up this card and hand-delivered it to me," said Brennan, who has traveled to Africa and Patagonia with Nancy but couldn't make the Galapagos trip. "It's like the message in a bottle. You never know if it's going to reach someone. This is the ultimate travel story."

Later, I called the letter writer, Nancy Buermeyer, to find out when she'd "mailed" the card. Amazingly, it was the day before I'd arrived in Post Office Bay.

"I mailed postcards to friends who did not get them yet," said the San Francisco resident. "Turns out you are more efficient than the Ecuadoran and U.S. postal services."

I asked her why, of all her friends and family, she chose Brennan to send a note to. Buermeyer explained her criteria, which were calculated to increase the odds of a delivery: The friend must live in a metropolitan area, in a building with an accessible mailbox or front door and "would be okay with having a wayward traveler showing up at your doorstep." Brennan passed on all counts.

For the note I posted at Floreana Island, I was less scientific, addressing it to the first person I could think of. I can't wait to hear how my trip to the Galapagos was.