Blue whales, the biggest animals on Earth, were not that large long ago. In fact, they were relatively small animals for most of their evolutionary existence, and they became as large as they are today only in the past 3 million years, according to a new study.

whales, climate change, ice age
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Blue whales were not so big initially

Whales are large. A bowhead whale can be 200,000 pounds, whereas a fin whale can be 140,000 pounds, but the largest of them all is the blue whale, which can reach up to 380,000 pounds, notes The New York Times. But according to researchers, climate change allowed these creatures to binge-eat and transformed them from a size of few meters to their present size of over 30 meters in only a few million years, reports ABC.

The study was done in collaboration between the Smithsonian National Museum of Natural History (NMNH) and the University of Chicago, and it was published in the Royal Society B’s Proceedings B journal. The study examined the fossil record of baleens, the group of filter feeders that includes blue whales.

Nick Pyenson from the Smithsonian’s National Museum of Natural History in Washington, D.C., said, “The blue whales, the fins and bowheads, and the right whales – they are among the most massive vertebrates to have ever lived.”

In an interview with the BBC, Pyenson said that some dinosaurs were longer, but these large fishes outweighed even the largest dinosaurs.

Pyenson added that people think of gigantism as being a fact of the geologic past but, “Here we are, living in the time of giants on Planet Earth.”

Onset of an ice age is a possible explanation

The lengths of about 63 extinct species were estimated by the research team, with species including some of the earliest baleens which swam in the seas and oceans more than 30 million years ago. The investigation was able to find evolutionary relationships between whales of different sizes by combining this data with data on modern whales, notes the BBC.

Pyenson said, “It’s like going from whales the size of minivans to longer than two school buses.”

The research team suspects that climate change about 4.5 million years ago essentially caused the baleen whales to become larger. They found that this period coincided with the early beginnings when ice sheets covered the Northern Hemisphere. The onset of the ice age is the best explanation for the increase in the size of these animals.

According to Graham Slater, lead author of the study, whales evolved so quickly that scientists could not even capture the change in the fossil records. Dr. Slater explained that the ice age saw several dramatic changes, including the closure of the Panamanian isthmus, which shut off the connection between the Pacific and Atlantic oceans.

If the scientists are right, then we can expect more ocean changes going forward. The experts warned that if man-made climate change warms the oceans steadily, then the seas will be more like they were when the whales were smaller.

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