I frequently do research on pseudoscience. One day, I was looking around a young-earth creationist website called AnswersinGenesis.org, perhaps some of you have heard of it. Anyway, I was watching the leader, one Ken Ham, talk to little kids about how evolution is wrong because it contradicts the Bible, and the Bible is “the history book of the universe”. He then proceeded to show a picture of a platypus and said how evolution couldn’t have resulted in such a creature. I have already seen enough of creationist bullshit to disregard it, but not being a biologist, I am curious: how DID the platypus come about? I have read about the scientific consensus on the matter, but it was a very technical read. I was wondering if someone could break it down into somewhat less professional jargon so as to be easier understood. Thank you for your contributions. 
I would have thought that the platypus actually shows transitional features which support evolution: the female exudes milk, but not from a nipple, more like a sweat gland; the male has poison spikes, similar to poisonous reptiles; the young are born from eggs, like reptiles, but the animal is warm-blooded like other mammals, and so on.
But I’ll wait for someone who actually knows what they’re talking about to weigh in.
The platypus is a monotreme, a distinct branch of mammals that lay eggs instead of live birth. The platypus and the echidnas are the only surviving species of monotreme. The monotremes seem to have split from the main branch of mammals before modern marsupials and placental mammals were distinct. There’s no reason the platypus wouldn’t evolve it’s unique characteristics. It’s rubbery snout that resembles a duck’s bill is not as extreme an adaptation as an elephants trunk. Many mammals have webbed feet. The tail is not as highly adapted as a beaver’s. The venomous spur is no more complex than a skunk’s scent gland. These are a set of uncommon characteristics in a mammal, but none of them so unique to consider the animal impossible to have evolved.
Genetic studies suggest that the monotremes (the platypus and the echidnas) diverged from other mammals (marsupials and placental mammals) more that 200 million years ago, i.e., in the Triassic period, before dinosaurs ruled the Earth. That’s surely long enough for some distinct features to have evolved.
They stuck a duck’s bill and an otter’s tail on the body of an opossum, at least that’s what they taught me in church!
But I am with Giles, long time isolation would lead to many unusual traits, I mean Electric Beaks WTF?
Really, you are approaching this the wrong way. Why couldn’t evolution result in the platypus? What is it about the platypus that singles it out as being something that couldn’t evolve?
The creationist argument isn’t meant to stand scrutiny - it’s debate rhetoric, for consumption by an enthused audience. If you try to follow it up with the person who claimed it, they’re likely to snort “Still on about that? I guess you need to justify your faith in evolution, eh?” or some such.
The only way that ‘evolution could not have come up with such a creature’ argument stands, would be if someone was claiming the platypus was transitional between otters and ducks, which (outside of creationist strawmen) nobody actually does.
I argued once with a guy who claimed that evolution couldn’t possibly come up with something as implausible and unfit for survival as a giraffe. I pointed out that if giraffes were in fact unfit for survival, there just would not be any giraffes.
I think the question ought really be, why would god create something like a platypus? To use up all the spare parts he still had around? As an in-joke? Because he’d created weed the day before, and thought it was just the funniest thing ever?
As a physicist I find the Bible’s description of the black-body background radiation spectrum left over from the Big Bang in the Book of Penzias and Wilson quite lovely, although Saint Gamow comes off as a bit of a Dicke.
My reaction is usually something like, consider “everything fits neatly into human convenient categories” and “everything is complicated and untidy and looks a real mess”. Now, which of those sounds most consistent with “deliberately designed by a perfect being for the benefit of humanity” and which of those sounds more like “just sort of happened”?
I mean, I agree things are often not the way they look, so you need to know the ACTUAL history, but to a naive glance, something like the platypus looks like evolution much more than design… 
The platypus only looks weird and ridiculous to us because many of its features resemble those of other, unrelated animals we’re familiar with. But if you came upon the creature as an unbiased observer from Epsilon Eridani, with no knowledge of other earth creatures, it wouldn’t strike you that way – you’d see how well-adapted it is to life in its environment, which would (to you) make a pretty good case for evolution.
That bill, for instance, is shaped well for straining out food from water. It superficially resembles a duck’s bill in shape (not surprisingly, since it does the same thing), but it’s structurally different. A Platypus bill isn’t hard likie a duck’s bill, but leathery. There are bones inside to support the structure, but they only provide a framework:
http://www.skullsunlimited.com/record_variant.php?id=4375
It has webbed feet that propel it around its watery environment, water-repeling fur, and the male has a poison spur for protection.
It lays eggs, which are more similar to reptile eggs than bird eggs (so another avian resemblance is more superficial than real, and another anomaly only to the mind familiar with other earth animals), and similar in many ways to those of aquatic reptiles, so it obviously serves them well. To my mind, calling this “transitional s[pecies” is a loaded term. It suggests that the only reason that the montremes lay eggs is because it was a necessary stopping-off point on the way to full vivipary, so they’rre stuck with it, the poor schmucks, because that was their lot in the great Evolutionary Lottery. Plsatyplus had to have eggs so that us higher mammals could have the advantages of live birth*. But evolution doesn’t work that way – the platypus isn’t the way it is because it’s a stopping-point on the way to somewhere else. It’s the way it is because it is the end product of random variation and environmental selection that fits its niche very well, indeed. It’s possible, I suppose, that a vivaporous platypus might be more successful in that niche, but no combination of random mutation plus natural selection has dislodged the existing platypus from its niche, so it appears that no viable changes have provided an advantage over what the platypous already has, which, to it, aren’t on a road to anywhere else.
*I think that Pepper Mill, given the choice when she was giving birth to MilliCal, would’ve opted for eggs.
Delightful comeback. That is the type of comment that needs delivering in an even, calm voice and be followed by a single finger pushing your glasses up the bridge of your nose.
Why is it that for me…
a) people rarely leave themselves so wide open
b) When they do I stumble for such a killing blow
No matter, I shall have that one tucked in my back pocket (along with a pair of glasses that I’ll pop on just for the occasion)
I can’t refute the argument, because it’s not an argument. It doesn’t say anything that can be refuted. “Evolution couldn’t produce the platypus.” Why? What, specifically, is it that can’t be evolved. I look at it and see a well-adapted, perfectly reasonable organism. “It’s funny-lookin’” isn’t a criticism of evolution. The only possible response is “Oh, yes it can. And did.” And there the debate rests until something more substantive is raised.
It’s very simple, but a little embarassing. One night a duck, and otter, and a scorpion got really drunk…
But seriously, why would God invent such an odd creature?
According to Robin Williams, the platypus was invented right after marijuana.
The OP isn’t advocating creationism, he’s just saying that come to think of it, he’s unfamiliar with the playpus’ evolutionary development and could someone please explain it in simple terms. Everyone seems to think he’s worrying about the possibility that ol’ Ken Ham might be correct, when he isn’t.
Don’t I remember hearing that a platypus has an incredible number of chromosomes?
[Karl Pilkington]
We don’t really need the platypus, do we? I mean, we’ve already got ducks and otters and opossums, right?. What’s the point?
[/KP]
I’m unfamiliar with platypus evolution as well, but here’s what Wikipedia has to say:
Moved MPSIMS --> GQ.
This is exactly correct. Monotremes retain certain basal features that Darwin’s theory predicts-- eg, that is all mammals evolved from organism that once laid eggs. That’s a key aspect of a scientific theory. It makes predictions about the real world.
The creationists are probably thinking that science claims the platypus evolved from placental mammals in a sort of “backwards” evolution. But the fact is, the platypus, and all it’s ancestors going back hundreds of millions of years, have laid eggs. Just as ours did, if we go back far enough. At some point, our ancestors evolved a different birthing process, while the platypus did not.