Whales, Barnacles, and Ancient Migrations: A Possible Break in One of Evolution’s Biggest Mysteries

What do barnacles have to do with prehistoric whale migration and evolution? A whole lot, according to UC Berkeley Ph.D. candidate Larry Taylor.

From their origins as four-legged, dog-like creatures in Pakistan to their present-day incarnations as “preposterously large” marine mammals that traverse the vast oceans, whales are the “poster child of evolution.” Millions of years is a lot of ground to cover, so that’s why Taylor decided to study humpback-whale barnacles. According to Taylor, barnacles are the secret to revealing migratory patterns of whales, and it has to do with the chemistry of their shells. The shells of barnacles vary according to the lighter and heavier oxygen isotopes found in seawater. In a cycle of rain and evaporation, the heaviest of oxygen isotopes remain at the equator, and the lightest remain moving towards the Arctic. Meanwhile, barnacles grow new bands of shell with each season, the compositions of which alter according to the isotopes found in the water. In other words, the growth band of a barnacle on a whale that is spending the season in the Arctic will reflect the lighter isotopes that are found there…right?

A breaching humpback whale. (Credit: NOAA)

As it turns out, this isn’t strictly true. Humpback whale barnacles have been shown to use more of the heavy oxygen isotopes in these colder regions. But that’s nothing geochemists and a “Greek-alphabet-soup of an equation” can’t fix. With this new data, then, Larry Taylor has been able to graph the isotopes against today’s oceans and, in turn, accurately follow the migrations of Alaska humpbacks (and the Alaskan humpback barnacle). As for prehistoric migrations, Taylor hopes to apply the same sort of methods to the isotopes of fossil barnacles.

So how did whales get so huge? Taylor’s already way ahead of us. And the answer is surprisingly simple: bigger whales mean farther distances may be covered. Farther distances mean greater access to increasingly scarce food sources, brought on by the ice ages. And if the vast migration patterns of today’s whales are the result of ice ages, then data gleaned from fossil barnacles may prove that prehistoric whales originally didn’t need to migrate in the first place.

There’s a lot more to the story of whale evolution, and the Atlantic article is well worth the read. The author, Peter Brannen, even presents a critical reflection on our own time:

Today human society is a geological force in its own right, and its an open question what its ultimate influence will be on the long evolutionary story of whales. The ocean is warming faster than it did even 56 million years ago, while ice sheets are poised for a collapse on time scales only seen at the end of the ice ages. But even before this global chemistry experiment gets completely out of hand, whales have alreadyrather acutelyfelt the influence of human civilization. Not that long ago, humans drew their oil, not from petroleum-soaked rocks, but from whales headsand Nantucket played the role of Abu Dhabi in this cetacean oil economy. Whale extinction was on Melvilles mind as he watched this global slaughter unfold, firsthand. He wondered whether Leviathan can long endure so wide a chase, and so remorseless a havoc.

Though the hunt has relented, and Leviathans numbers have recovered somewhat, genetic studies indicate that populations of North Atlantic humpbacks were once 20 times more abundant than present. And given that climate and oceanography have played such an important role in whales evolutionary past, through ice ages and super-greenhouses both, what will their future hold in an ocean thats not only rapidly warming but quickly acidifying as well?

And in true Core fashion, Brannen makes an astute observation on the very nature of geology, which, we think, applies to most, if not all of the subjects we learn in Core:

Like any subject in geology, pull on one thread–in this case, humpback whale barnacles–and all of Earths history begins to unspool. To understand an animal you have to understand its history, and to understand its history you have to first understand the history of the earthand beyond. Indeed, whales even benefited from the influence of outer space as well, as the asteroid that executed T. Rex also cleared the ocean of its sea monsters, inviting that dog-like ancestor of all whales to colonize the seas ages ago.

Read the whole article on The Atlantic.

Post a Comment

Your email address is never shared. Required fields are marked *