Baleen whales of today are the largest animals to have ever lived on the planet and have a lot of blubber. The biggest of them is the blue whale, almost 100 feet long and 200 tons. A new theory for why and when baleen whales got to be so big is reported in a study published recently in the Proceedings of the Royal Society B. (1)
The team measured the skulls of 63 extinct whale species from the fossil collection at the Smithsonian Institution’s National Museum of Natural History. Their analysis concluded that whale body length had varied randomly for about 30 million years before making a leap to more than 32 feet between 4.5 million and hundreds of thousands of years ago—a stretch of time that corresponds to the epochs when humanoids and humans came around, commonly referred to as the Plio-Pleistocene—which is pretty recent and quicker and newer than previous research suggested.
Pegging the trend toward giant sizes to the Plio-Pleistocene ruled out other hypotheses as to the cause, such as the threat of predation by the huge shark megalodon—which had already been around for millions of years before the whales’ growth spurt — or the advent of filter feeding, which had been around for more than 15 million years at that point, although those were side benefits of biggness when it came. Also being biggly has non specific benefits of the lower metabolic costs of low surface area per volume and the ability to migrate great distances. Being this big is also easier in water than on land and salt water is more boyant than fresh water. These monsters of the deep can also swim very fast and efficiently. Human predation however has changed all that and made the possibility of whale extinction real.
The theory proposed by these investigators of why this happened now traces whales’ increasing size to changes in food availability resulting from ice ages. As an ice cap formed at the North Pole, freshly cooled water would sink to the bottom of the ocean and then rise again where winds pushed warm surface waters away from the coasts in a seasonal phenomenon known as upwelling. This upward rush of cold water would have brought nutrients to the surface, allowing phytoplankton to bloom and whale prey such as plankton and krill to flourish in dense patches at certain times of the year. Such conditions would have offered an evolutionary boon to a bigger baleen whale. A larger mouth would mean taking in more water and filtering out more prey per gulp.
So there it is, cheap abundant rich food made these biggest creatures, who eat the smallest creatures, fat.
John DiTraglia M.D. is a Pediatrician in Portsmouth. He can be reached by e-mail- [email protected] or phone-354-6605.