Scientists Uncover the 40-Million-Year-Old Evolutionary Tree of Baleen Whales

Baleen whales are the largest animals to ever live on Earth and now, new research is providing the most comprehensive picture ever of their evolutionary history. The findings reveal new insights into the extraordinary history of these whales.

Most mammals feed on plants or grab a single prey animal at a time. Baleen whales, though, are famous for their gigantic mouths and the ability to gulp and filter an enormous volume of water and food.

In this latest study, the researchers created a comprehensive family tree of living and extinct baleen whales stretching back nearly 40 million years. Similar family trees have been constructed before, but this one is by far the largest and, crucially, the first to be directly calibrated using many dated fossils.

The new research reveals which whales are related and exactly how long ago every branch of the tree, whether extinct or still alive, first rose.

"We find that the earliest baleen whales underwent an adaptive radiation, or sudden 'evolutionary burst,' similar to that of 'Darwin's finches' on the Galapagos Islands," said Ewan Fordyce, one of the researchers, in a news release.

The early phase of whale evolution coincided with a period of global cooling. At the same time, the Southern Ocean opened, and gave rise to a strong, circum-Antarctic current that today provides many of the nutrients sustaining the modern global ocean.

During whales' early history, they branched out into many different lineages with different body shapes and feeding strategies. Eventually, toothed 'baleen' whales disappeared, leaving behind only their filter-feeding cousins.

The findings reveal a bit more about the history of these whales. This, in turn, may tell scientists a bit more about conservation strategies for the future.

The findings are published in the journal Royal Society Open Science.

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