don't judge a book by its cover.
topic of the day 059 & video of the day 052
how evolution turns a possum into a wolf
What, who, when, how, why? Then, so?
Thylacine aka Tasmanian wolf aka Tasmanian tiger, is, despite its appearance, is not a wolf or a dog, but rather a marsupial.
Fossils and DNA tell us that mammals like wolfs and mammals with pouches last shared a common ancestor about 160 million years ago. Another pair? A hummingbird and a Velociraptor!
The thylacine is about as distantly related from a wolf or a fox as it can be despite the long legs built for running, skulls for sniffing, and massive muscle attachments for biting. How is this two animals this distantly related could come to share so many similarities?
There are two biological explanations for the similarity.
First, two animals can be similar because they shared a common ancestor i.e. wolves and coyotes for example.
Another is convergent evolution, which means two animals their descendants have evolved to be similar to one another through the action of natural selection.
If we go back to the common ancestor between us and the penguins, it already had legs and they were built a lot like ours. This is called homologous, having the traits being inherited from a common ancestor.
But the common ancestors between us and the ant was so long ago that it didn't have legs. Our ancestors and ant ancestors evolved legs independently, with this similarities called analogous.
This is the result of convergent evolution, i.e. how the wolf and thylacine walk.
We are plantigrade animals, who put their whole foot flat on the ground.
Possums, the ancient ancestor of the tasmanian wolf, are plantigrade animals just like us.
When a dog and a wolf stands, their heels are up in the air while standing on their toes.
The tasmanian wolf keeps its heel off the ground and walking on their toes as well.
Despite coming from different ancestors, the wolf and thylacine independently evolves this analogous trait: walking on their toes.
Another example is between a bird and a bat. Their ancestors already had a forelimb, a homologous trait but using that arm-like things as a wing evolved independently in both of them, so flying with them is an analogous trait. There are so many clear examples in the video above.
The key to convergent evolution is a similar environment.
Conditions like the climate, competition and what's food around determine which traits are favored more than others.
In the open ocean, a streamlined body and powerful swimming tail is proven to work, and we seen it all kinds of fishes. Just like how how legless body seems to work pretty well underground.
These are just examples of similar body shapes and anatomy, but behaviours can be convergent too. Just ask a bat and a dolphin.
There's no such thing as "perfect" traits, considering how different octopus is with fish and bear with dog.
"Not all similarities are the same."
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