Channeling Karl Pilkington: But what do they do? That’s what I want to know. Why do we need 'em? Like seals, they’re halfway between a fish and a dog. We already have fish and dogs; why do we need something halfway?
Specifically, it’s an “argument from personal incredulity” -IOW, what I have trouble believing is probably not true.
What if God smoked cannabis?
Do you suppose he had a buzz
When he made the platypus
When he created earth, our home?
Does He like Pearl Jam or the Stones?
I agree with this approach, but sometimes take it from the other side. I reply with something like “what is in your (mis)understanding of evolution that makes you think it could not produce the platypus”?
I think my response to such a claim would be even more succinct. It would be something like “Huh?”.
The extant monotremes are excellent examples of organisms that retain a few basal, that is, ancestral features of the mammalian lineage, while showing many derived characters. (In the past, basal characters were often described as “primitive,” and derived ones as “advanced,” but because they imply value judgements of the characters these terms have largely been abandoned.)
The monotremes retain several reptilian characters that have been lost or modified in other mammals, including egg-laying and certain features of the skeleton. However, they have several derived characters that separate them from reptiles and unite them with other mammals, including milk, hair, and three inner ear bones.
But platypuses and echidnas are both very highly specialized animals with characters that make them very different from the ancestral mammal. Both have toothless beaks. The platypus is highly modified for aquatic life, and echidnas for ant-eating. So in this sense they are very far from the “primitive” mammalian condition.
The fact that they are oviparous is probably the single biggest reason for the platypus’ success. The primitive[sup]*[/sup] condition for monotremes is basically marsupial. The females carry the eggs and young in a rudimentary pouch. However because they lay eggs, they can also leave the eggs and young in temporary nests when conditions are right, and it was this ability to lave the young that pre-adapted the platypus to an aquatic life.
Until very recently (in geologic terms) platypuses were the only aquatic mammals in Australia while the other continents were home to hundreds of species. Even today, Australia has only 3 aquatic mammal species, and the other two are rats. This is one of the truly astonishing quirks of the Australian fauna that I think is greatly overlooked. Australia has an almost total absence of aquatic mammals. No shrews, no otters, no capybaras, no hippos, no beavers. Nothing except a platypus and a couple of rats. There are vast ecological niches utterly unexploited in Australia. It’s as bizarre as if the Americas had no grazing animals or Africa had no arboreal mammals. Yet nobody ever comments on this glaring oddity.
Marsupials have a major problem evolving into the the aquatic niche. Because the young are carried in a pouch, they drown when the mother enters the water. Their is one South American marsupial that has managed to overcome that by some convoluted rearrangements of the pouch and the haemoglobin structure and repiratory physiology of the young, but it’s strictly a one off. There are no other aquatic marsupials.
The reason why the platypus is successful is because it evolved in an environment with absolutely no competition, and that was made possible because it lays eggs. And because they are essentially marsupial themselves, there was no obvious way for a platypus to become viviparous until i6t was already a successful platytpus, at which point it was kinda redundant.
- Added to annoy Colibri.
Those niches are exploited in Oz - just not by mammals. Crocodiles, snakes and monitor lizards occupy the niches that, elsewhere in the world, are occupied by aquatic mammals (or birds)
Except that isn’t true.
First off, elsewhere in the world also has crocodiles, snakes and monitor lizards. The species in Australia are utterly unremarkable representatives of their clades. Australia isn’t even particularly diverse in those clades. For example it has fewer crocodiles or aquatic snakes than Africa, Asia or South America.
Simultaneously elsewhere in the world that has crocodiles, snakes and monitor lizards also have a diverse suite of aquatic mammals, so clearly the niche of aquatic mammal is not being filled by crocodiles, snakes and monitor lizards.
For example, can you tell me which crocodile, snake or monitor lizards is occupying the niche filled elsewhere by water buffalo, hippos or capybara : a large grazing animal specialising in riparian vegetation. Or which species of crocodile, snake or monitor lizards is occupying the niche of otter: a fast moving aquatic predator? The fact that a rat recently has evolved to occupy the otter niche is really all the evidence that is needed that such a niche wasn’t being exploited by reptiles. Australia doesn’t even have an equivalents to the genets, minks, bush dogs or raccoons that are semi-aquatic omnivores. There just aren’t any animals exploiting these niches. This is a large part of the reason why water buffalo are such a major problem. Australia’s wetlands produce massive amounts of food for which there is no absolutely no competition for at least 4 months of the year. Aborigines had to abandon the wetlands for several months of every year because there is simply no source of protein available, yet this is the season of the greatest vegetation growth.
An interesting addition to the thread, but why did you semiquote me so that I appear to be saying the exact opposite of what I said? The whole sentence reads:
I had understood that the concept of vacant niches was somewhat controversial, but I’ll just withdraw my point, as it’s clear you’re using a very much more specified definition of ‘niche’ than I had imagined.
To give Ogden Nash a subject?
This is the interesting part. You explained why marsupials didn’t become aquatic, but it is unusual to see this niche unfilled. Aquatic mammals have had a great impact in other parts of the world. Australia is unique geographically, but I wonder what a beaver or some hippos would have done to the landscape.
ETA: Ok, it would probably take more than one beaver.
Rational arguments don’t usually work on religious people. Otherwise, there wouldn’t be religious people.
Doris Egan, House M.D., The Right Stuff, 2007
Usually, but not always. There’s evidence on this board that occasionally a true believer listens to reason.
But it’s also easy for people to be confused about evolution even if they aren’t influenced by religion. Among those who accept evolution as science, there are still plenty of people who don’t get it. Faced with a platypus (and it’s never fun getting hit in the face with a platypus), people’s misconceptions about evolution get highlighted. The platypus is actually an excellent example of evolution, adaptation to an environment.
Karl Pilkington, for example:
– “Bacteria, fish, mermaid, man.”
– “Maybe if we hadn’t invented planes, and what-have-you, maybe we’d be able to fly.”
Agree. Some of the silliest “facts” about evolution are “known” by people who are entirely comfortable with it. We see it in this forum all the time.
Likewise, why would he give the female two ovaries where only the left one is functional? (According to Wikipedia.)
God was stoned off his ass, and had a box of spare parts leftover from when he made all the other animals.
It’s science.
Do you think the male platypi have psychological issues because they weren’t breast fed? And do you think the female playtpi have spur envy?