Evolution and the Ocean
Where can you see results from the world’s oldest and biggest migration? Just hike two miles down Damnation Trail south of Crescent City. You will see sea stars purple, orange and red, all in the same individual. Sea anemones sport aquamarine and purple. They look more like flowers than animals, hence the name. And, yes, sea cucumbers resemble orange and yellow vegetables.
These animals seem so unusual that we name them after more familiar animals. They look weird because they got left behind. Maybe these circular sea animals didn’t know which way to turn to get to land, unlike animals we are familiar with left and right sides, like ourselves. Isopod crustaceans made it to land as pill bugs. The very similar amphipods, though, only made it from ocean to groundwater. They never became terrestrial like pill bugs, probably because their more vertical body shape would have made them top-heavy on land.
Half a billion years of migrating to once lifeless land has largely ended. Land insects and flowers and marine crustaceans and seaweed became so dominant that boundary markers say “No newcomers allowed.” These major groups can’t be out-competed on their home turf. It’s why seafood is crustaceans and mollusks, not tasty insects. It’s why we eat vegetables, not seaweed.
Mammals, though, got a break. A meteor likely killed dinosaurs and marine reptiles. With the competition gone, whale ancestors took the plunge within 15 million years. Starting so early whales now have more marine adaptations like fins than more recent migrants. There were otter-like hippo descendants 55 million years ago, seal-like whales 50 million years ago, dolphin-like whales 30 million years ago, and whale-like whales a mere ten million years ago. How can you tell the original residents like fish from mammal newcomers? Watch how they swim. Under the threat of gravity, mammals reinforced their backbones while living on land. So now they can only swim up and down. Fish, on the other hand, swim by moving sideways.
Fossils, radioactivity, and DNA clocks chart these migrations. Closer to home is a reminder of what helped our ancestors move from sea to land. If you cut your finger, taste what oozes out. Blood has the same saltiness as the sea.
And if you are wondering how Damnation Trail got its name, you won’t find out going down the trail. But you do hike back over a thousand feet above saltwater.
Did You Know?
Scorpions fluoresce or glow under ultraviolet (UV) black light. They can glow electric green or blue. Scorpions fluoresce because they contain a fluorescent protein in the upper layer of their exoskeleton. This layer is like your fingernail, but even more protective and tough. The special protein inside is thought by scientists to serve as an ultraviolet sensitivity mechanism, perhaps allowing the scorpion to avoid burning itself by staying exposed too long to damaging light levels.