Last year Nature Matters featured some of nature’s record holders. One blog in particular featured the largest animal which ever lived – the blue whale. Now, blue whales may be the most massive creatures the Earth has ever known but new research shows they only recently became so big. Recently in the geological sense of the word – about 3 million years ago.
Whales have been around for 50 million years, which is a very long time. The first humans, our ancestors Ardipithecus ramidus, didn’t show up until 4 million years ago. Now scientists studying the whales’ fossils record have found that, for most of that time, the animals were relatively small.
Up until 3 million years ago, whales remained the same size. But then, almost overnight, the smaller species died out and the giants of today appeared on the scene. What drove such a dramatic evolutionary change? The answer is one which is affecting the world today – climate change.
North and South America were once two separate islands but 3 million years ago they came together to form one huge landmass. This stopped the waters of the Atlantic and Pacific Oceans from mingling. Which in turn brought about an ice age. Most people don’t know it but we are still living in an ice age today (an ice age is defined as any period in which the poles are frozen).
Lots of large animals evolved to live in the ice age – mammoths, giant sloths and woolly rhinos for example. These are now extinct but the giant whales remain. The reason is that the conditions they need to live are still here.
You see, the new ocean currents created by the changing climate created food ‘hotspots’. Nutrient-rich water rising from the sea bed became havens for masses of small creatures like krill – a favourite of whales. This abundance of food fuelled the whales’ growth, leading to the 30 metre leviathans we see today.
Today the climate is changing again. Because of the pollution us humans create, the world is warming and the ice age is ending. How will this affect the whales? We don’t yet know but it seems likely that the food they have come to depend on may run out. If it does that will mean an end for the largest animals ever. Now wouldn’t that be a tragedy?
To find out more about the natural world and the amazing creatures who live there, have a look at the Nature section of our site. It contains more than 60 quizzes which are all free to play. You’ll find questions on birds, mammals, invertebrates, fish, reptiles, amphibians, trees, flowers, minerals and even outer space! There’s bound to be something of interest there for you!