Micro Life Zone
Asked by brownyy to Arti, Chris, Dustin, James, Steven on 23 May 2012.
Keywords: evolution, whale
Dustin asked for this question and I think I’ll leave it to him.
Spoiler alert though, look out for the bit when the whales started to walk 🙂
Dustin did ask for this question , so I’ll leave it for him to answer as well.
I did just looked this up and read about it – it does sound pretty interesting! 🙂
GREAT QUESTION. Whale evolution is fascinating.
Whales belong to the order of animals called cetaceans and stretch back about 55 million years. But their evolution only took about 15-20 million years to make the full transition from land animal to their current forms.
If we look at the still living cetaceans, they are broken into two major groups, baleen whales and toothed whales. Baleen whales include the massive whales like humpbacks and the blue whale, and toothed whales include all dolphins, orcas, and belugas (there are many many more). These two groups have been around for about 35 – 40 million years
So what happen between 55 million years ago and 40 million years ago.
When we trace the story all the way back, it appears that the ancestors of whales actually lived on land. Pakicetus is thought to be the closest living relative to the direct answer of modern whales, and if you saw one now and was asked what it looked like, you would likely say a wolf.
From that time, we have a great fossil record of animals becoming more and more aquatic. Their legs reduced and changed to become flippers, tail became longer and more like a paddle for swimming, and skull structure changed so that the nostrils moved to the top of the head to form what we call the blowhole.
In fact, if you see a whale skeleton in a museum, you will see that they still have vestigial rear legs.
It is interesting, because another group of mammals have made a similar journey to the water, pinnipeds. Pinnipeds are the group of animals made up of seals and walrus. By looking at them we can see that they haven’t undergone the same dramatic change that whales did. Pinnipeds evolved from something like a bear about 20-25 million years ago. Rather than evolving a tail though, they still swim with back legs and it is their tails that have greatly reduced.
These sorts of things is what got me very interested in evolution and biogeography.
This is a great diagram showing the evolution, and time line.
By BRIDGE8 under license from Mangorolla CIC 2019