The Platypus: Half Mammal Half Reptile?

The platypus: for most of us, it is one of those quirky creatures from Australia that one day we hope to see. From an evolutionary standpoint, however, the platypus is fascinating.

An animal that produces milk for its young, yet at the same time lays eggs? A cute, furry, webbed-footed creature that can also release venom so strong modern-day painkillers are useless to affected humans? Rumor has it that at first glance, it was so bizarre that the animal wasn’t even believed to be real, but a mish-mash of others that were assembled together.

And rightly so: When studying the animal kingdom in school, mammals were completely distinct from reptiles. However, the platypus seems to be a unique combination of both.

In 2008, an article in Nature dove deep into the animal’s genome, finding some pretty unique characteristics. Its genetic sequence represented the characteristics we see, that the genome had a combination of mammalian and reptilian components.

And, perhaps just to throw us off, the biological process of determining whether a platypus will be male or female is most like birds. Fascinating.

Believe it or not, the platypus is actually telling us a lot about evolutionary processes. For instance, it highlights what happened when mammals split from reptiles along the evolutionary tree.

In addition, it demonstrates how ‘convergent evolution’ can occur. Back in 2010, an article published in Genome Biology found that it contains over 80 toxin genes from 13 toxin families, which were homologous to fish, other reptiles, spiders and starfish. Although these are completely different species, the traits seemed to evolve independently.


The platypus: Mammal? Reptile? Or just plain enigma?

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