Tuesday, January 11, 2011

Evolution and monotremes, spam and off-topic Google searches

This post will discuss monotremes in evolution, but first a diversion to the reason for this topic.

I got a comment submitted from "Izumu":

"Hi Stephen,
I am Izumi from TBS TV, a Japanese TV company. We are intersted in the platypus egg photo you posted on your blog of 19 Mar 2008. I couldn't find your email address and that's why I'm making comment trying to be in touch with you. Could you kindly write me back to xxxxx@nifty.com ? Please don't post my comment since it includes my email address. Thank you very much for your coopereation. Izumi "

I post a reproduction of this comment sans email address, although I was inclined to include it anyway.

I get quite a number of spam comments posted, which is why comments are moderated.  I'm not inclined to reply to this request directly, because:
a) It was off topic;
b) The email address wasn't from an official TBS domain - Nifty is just a Japanese ISP.

Usually I just mark spam as spam.  I don't usually get a comment that's so close to falling either way.

There's a few pictures of platypus eggs on the web.  As it happens, mine is now at the top of Google Images.  It was a bit of a tragedy in some ways, because the actual topic of the post was the evolution of milk, but it gets caught in the wrong net.  If you want to communicate about platypus eggs, talk to someone who's communicating about platypus eggs.

The reason they appear to us to be strange is just a quirk of evolution: they are the last representatives of the earliest types of mammal.  The only egg-laying mammals (protherians) left are the monotremes, two species of echidna (porcupine-like creatures) and one of platypus, all native to Australia/Papua New Guinea.  Yet the first mammals were egg-layers.  Marsupials (metatherians: live but under-developed birth) and then placentals (eutherians: live birth) were a much more recent development, as the technology of birth evolved over tens of millions of years.

The oddness of the platypus may initially be due to their appearance, including webbed feet and a duck-like bill.  The fact that  they're mammals that lay eggs draws people in more.  But they are distinctive for two more reasons: they have poisonous spurs on their ankles (which seem to be for breeding purposes!), and they hunt through muddy water by sensing electrical fields.

The platypus, in evolutionary terms, is not so odd.  Pretty much all these features have evolved separately in other animals.  That's evolution: the time spans involved are so vast that if mutation can produce a lasting feature once, it can do it again.

No, the true oddness of the platypus lies in its survival to a time where most of its features are seen as uncommon.  There's a warning there: the survival of features that do not catch on (radiate) more broadly - in numbers or variety - is more indicative of desparately clinging to a vanishing niche than of evolutionary success.

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