Op-Ed: The Platypus Genome is exactly what it looks like, genetically

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It’s also a key to the evolutionary process. The platypus belongs to an order of animals called monotremes. The other monotreme is the echidna, the Australian equivalent of a porcupine/aardvark. These are the oldest living mammalian life forms on Earth. The platypus just happens to produce venom exactly like a snake, and has genes related to reproduction which are exactly like a bird.

The Sydney Morning Herald:

According to a study released Wednesday, the egg-laying critter is a genetic potpourri -- part bird, part reptile and part lactating mammal.

The task of laying bare the platypus genome of 2.2 billion base pairs spread across 18,500 genes has taken several years, but will do far more than satisfy the curiosity of just biologists, say the researchers.

"The platypus genome is extremely important, because it is the missing link in our understanding of how we and other mammals first evolved," explained Oxford University's Chris Ponting, one of the study's architects.

"This is our ticket back in time to when all mammals laid eggs while suckling their young on milk."

Native to eastern Australia and Tasmania, the semi-aquatic platypus is thought to have split off from a common ancestor shared with humans approximately 170 million years ago.

The creature is so strange that when the first stuffed specimens arrived in Europe at the end of the 18th century, biologists believed they were looking at a taxidermist's hoax, a composite stitched together from the body of a beaver and the snout of a giant duck.

Just for the record, 170 million years ago is roughly the mid-Jurassic.

The genome has now been sequenced, but reading the rest of the information, exactly how the platypus came to have this truly strange mix of genes is anyone’s guess.

Genes are inherited. So this is some family. The platypus has apparently retained genes from its ancient ancestry.

That’s more than slightly interesting, because according to natural selection, it means that those genes have been serving useful survival functions for all that time. Natural selection also means that these genes have been functioning all the way back to the reptilian ancestry, because they’ve been retained.

The order of evolution is reptile/bird/mammal. All are related. Ancient mammals did exist at the time of the dinosaurs, as minor fauna, as did very primitive birds.

Following the trail, it therefore supposes that a series of links has operated to produce the platypus, which really isn’t a reptile, nor a bird, nor a mammal.

A common ancestor could, in theory, have developed genes which operate like reptilian, avian, and mammalian genes. The three types can’t share genes, or interbreed.

The only working hypothesis I can see is that this species was involved in a progression of genetic acquisitions.

It was able to acquire the reptilian and avian genes as useful mechanisms, prior to its evolution into a modern platypus. Or it acquired genes which have developed into genes like those seen in reptiles and birds.

So what was this animal?

The platypus is a specialist aquatic animal. The duck bill is a direct adaption to its lifestyle. There is evidence of a prior jaw structure, from memory, but it’s a ghost of its ancestry.

Interestingly, its environment is a clue, of sorts. The diet of freshwater animals it now lives upon also existed at the time of its ancestors. It is, theoretically, possible that one animal could have evolved in the same habitat through the millions of years.

There’s an obscure clue here. In the era preceding the Jurassic, there were animals called “mammal like reptiles”, complete with fur. According to studies, only the jaws showed they were actually reptiles. Even in the Jurassic, there’s some evidence that Allosauri with fur were present in Australia, which was then much closer to Antarctica, quite possibly even still joined, according to some theories.

So an aquatic mammal like reptile, an early one, with the same relationship to birds as the dinosaurs, which is now known to be a very close relationship, isn’t out of the question. It’d be an unknown species, because none of the other mammal like reptiles vaguely resembles a platypus. Many of them were also predators, with mammal like bones, different morphology entirely.

However- it does explain the biology. Bird genes don’t just happen to occur in an animal which isn’t a bird. To develop bird genes requires a similar, related biology, at least. Ditto reptile genes.

Apparently the platypus picked its relatives very effectively.