A humpback whale was spotted in New York Harbor near the Statue of Liberty, NBC News reported. The marine mammal spent hours swimming along the city shoreline, surfacing every minute or so for breath. Long ago, whales left land and headed back to sea.
According to NBC News, a rare visitor recently came out to play in New York Harbor. “A humpback whale was ready for its close-up [and] frolicked in front of the Statue of Liberty, One World Trade Center, and other iconic sights off New York Harbor,” the article said. “The U.S. Coast Guard confirmed reports of the sighting, but said it would get involved only if the whale became entangled or otherwise became endangered.
“For hours, the whale surfaced every minute or so for a breath, making its way past New York’s shoreline with sites like the Empire State building in the background.”
On the subject of whales breathing, their need to surface for air is an evolutionary byproduct of their ancestors having once lived on land. However, we generally think of evolution as involving a sea-to-land migration.
Life Is Better Down Where It’s Wetter
So why did proto-whales turn tail and head back to the ocean? Maybe we’re mistaken in assuming the unidirectional move of evolving life.
“It is very easy to give the impression that there is some sort of teleological motivation driving evolution,” said Dr. Stuart Sutherland, Professor in the Department of Earth, Ocean, and Atmospheric Sciences at The University of British Columbia. “It is important to understand that evolution does not have a goal in mind—it is not a matter of design.”
Dr. Sutherland said that natural selection occurs in particular environments, as those environments change, based on physical and biological shifts through time. Organisms’ characteristics and mutations aren’t produced because they choose to evolve them; they evolve through natural selection over long periods of time.
“The proto-whales did not consciously move back into the oceans, forcing their own evolution in some way,” he said. “Rather, certain forms would have a selective advantage allowing them to inhabit increasingly more aquatic environments in a step-by-step manner over millions of years.”
Geologically Speaking, It’s Pretty Quick
Whales are part of an aquatic group of animals called cetaceans, which also includes dolphins and porpoises. The oldest cetacean for which we have fossil evidence, Dr. Sutherland said, is the extinct genus Pakicetus, a 6.6-foot-long creature that lived on floodwater plains.
On the other hand, the first completely aquatic whale was the Basilosaurus, named as such because it was first believed to have been similar to Mosasaurs and Pliosaurs. Comparing the modern whale and the Basilosaurus helps us to understand why whales moved back to the sea.
“From the first terrestrially adapted cetaceans like Pakicetus, at 50 million years ago, to the first obligate aquatic members of the whale family such as Basilosaurus, at around 41 million years ago, it took just nine million years of evolution to radically transform this group of mammals,” Dr. Sutherland said.
“It shows how rapidly natural selection can operate when a group of creatures radiates to fill a relatively unoccupied niche; in this case, a niche left vacant by the giant Mesozoic aquatic reptiles following the end-Cretaceous extinction event.”
One paleontological site, Cerro Ballena, is rich with fossils and shows the final piece of the puzzle. This site dates back to somewhere between six and nine million years ago. The fossils show that the whales had already evolved much closer to their modern appearance.
By following the evolutionary trail back through common ancestors, we can see how whales performed what looks like one of the great U-turns in biology.
Dr. Stuart Sutherland contributed to this article. Dr. Sutherland is a Professor in the Department of Earth, Ocean and Atmospheric Sciences at The University of British Columbia (UBC). Raised in the United Kingdom, he earned an undergraduate degree in geology from the University of Plymouth and a PhD in Geological Sciences from the University of Leicester for his studies on Silurian microfossils called chitinozoa.