A blue whale off the coast of MexicoNorbert Wu/Minden Pictures/FLPA By Adam VaughanMany species of whale may have become giants much earlier than previously thought. It was believed that the 15 species of baleen whales rapidly jumped in size about 2.5 million years ago, from typically around 5-6 metres to 10-15 metres or as much as 30 metres in the case of blue whales. One dominant explanation was that a sudden shift in the climate changed the food available to them. This meant that there were patches of ocean that were very dense in food, so whales had to eat large amounts at each spot, before travelling long distances to the next one. Advertisement Excavation of the blue whale fossil on the edge of San Giuliano Lake, ItalyG. Bianucci Now, a new analysis has found that whales could have ballooned in size as far back as 10 million years ago, and gradually rather than suddenly. Felix Marx of Monash University in Australia and colleagues reached the conclusion after dating a “truly titanic” 26-metre long blue whale fossil found in Italy and several other whales in the Peruvian desert. They compared the dates and sizes with existing fossils. The huge blue whale appears to be about 1.2-1.5 million years old. To get to such a big size, whales would have needed a long lead-in time to evolve, says Marx. The implication of the study is that whales have been shaping the oceans for a much longer time than we thought. As well as consuming a huge amount of marine life, their sheer size means their travels play a key role in moving nutrients around by mixing water from different depths. “There is a lot more to learn about how gigantic whales have shaped the evolution of the ocean ecosystem,” says Marx. Journal reference: Biology Letters, DOI: 10.1098/rsbl.2019.0175 More on these topics: whales
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