The theory of evolution began in the Galápagos. As seas warm, the greatest evolutionary test yet may be at hand.

ALCEDO VOLCANO, Galápagos — When the clouds break, the equatorial sun bears down on the crater of this steaming volcano, revealing a watery landscape where the theory of evolution began to be conceived.

Across a shallow strip of sea lies the island of Santiago, where Charles Darwin once sighted marine iguanas, the only lizard that scours the ocean for food. Finches, the product of slow generational flux, dart by. Now, in the era of climate change, they might be no match for the whims of natural selection.

In the struggle against extinction on these islands, Darwin saw a blueprint for the origin of every species, including humans. Yet not even Darwin could have imagined what awaited the Galápagos, where the stage is set for perhaps the greatest evolutionary test yet.

As climate change warms the world’s oceans, these islands are a crucible. And scientists are worried. Not only do the Galápagos sit at the intersection of three ocean currents, they are in the cross hairs of one of the world’s most destructive weather patterns, El Niño, which causes rapid, extreme ocean heating across the Eastern Pacific tropics.

Research published in 2014 by more than a dozen climate scientists warned that rising ocean temperatures were making El Niño both more frequent and more intense. Unesco, the United Nations educational and cultural agency, now warns that the Galápagos Islands are one of the places most vulnerable to the impacts of climate change.

To see the future of the Galápagos, look to