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Convergent Evolution Upends Honeyeaters' Taxonomy
grrlscientist writes in with a beautiful piece of science, beautifully explicated. The poignant bit is that the birds in question are all extinct. "Every once in awhile, I will read a scientific paper that astonishes and delights me so much that I can hardly wait to tell you all about it. Such is the situation with a newly published paper about the Hawai'ian Honeyeaters. In short, due to the remarkable power of convergent evolution, Hawai'ian Honeyeaters have thoroughly deceived taxonomists and ornithologists as to their true origin and identity for more than 200 years."
There have been debates over the taxonomy of odd creatures (with similarities to other known creatures) forever. Sometimes simple physical resemblence just doesn't really tell the tale. Of course, evolution producing similar looking/behaving birds is nothing new either (just look at how similar African parrots and South American parrots are to one another).
The really great debates come when zoologists get into trying to classify an animal that looks like (or behaves like) two DIFFERENT known creatures. One of my personal favorites is the Red Panda. The bottom of its body and claws look like a bear's (you can see it clearly in this picture) and it eats only bamboo, just like a Giant Panda. But the rest of it looks like a raccoon. This cute little furball finally had to be given its own unique family, because no one was quite sure where to put the little bastard. And it's still debatable if it truly deserves its own family.
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Proposed text: "Evolution, like gravity, is just a theory. Please act accordingly."
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I realize that in this case (being dead for 200 years) it is more difficult, but why don't they _just_ use DNA sequencing to determine the classification of animals?
Observation (of both behaviour and appearance) is influenced by the observer and is variable. Two people never see the same thing the same way. Ask a man and wife what colour the living-room couch is and you will get two different answers! =)
The DNA sequence will never lie, and that sequence will tell us FAR more about common evolutionary traits then our eyeballs will.
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Ah, thanks for the kind invitation to join your discussions. i wish i had more time to do so, but alas, i have only a few hours per day of internet access, so i spend most of that time looking for papers to write about and answering emails as well as publishing my essays and images. but i will try to make more of an effort to comment here now and again!
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I was always impressed by the similarities between sharks, dolphins, and icthyosaurs. Similarly, there's a phenomenal similarity between the flying reptiles such as the pterodactyls and bats with finger bones modified with flaps of skin to make wings. There's also the similarities between various species of gliding tree mammals, the flying squirrels and lemurs and the like. One can also talk of amazing developments with marsupials which had armored herbivores similar to a rhino and carnivores like a leopard-form. (and let's not forget that a Triceratops is built awfully similar to a rhino down to the armored hide, horns, and heavy, stocky legs.) All of these from obviously unrelated lines of descent converging on similar forms to satisfy ecological niches. If I recall correctly, there's also a type of fish that developed a false-placenta for live-birthed young -- it's not a true placenta because it isn't a placental animal but it serves the same purpose. I believe this fish was in the extended shark family.
The other thing that really amazes me is how the theory of evolution makes certain predictions that you'll simply not see contradicted. For example, there's the general rule that animals will adapt existing limbs for various purposes so you might see a rodent develop forelimbs into wings but you will not see a rodent sprout brand new wings from its back while retaining the previous four limbs. Even the weirdest body parts you can find can be seen to be modifications, not wholly new structures sprung forth from nothing. You won't see a bird suddenly come with three eyes or an elephant with a cyclopean eye or a cat with eight legs like a spider (barring genetic defects that will be unable to reproduce).
What's also amazing is how the lines between species get blurry. The old definition is that two populations are split as a species when they cannot interbred and create viable offspring. But we've seen from zoos that populations that don't mix in the wild can produce viable offspring such as ligers, tygons, then there's the blonde grizzlies that are a hybrid of grizzly and polar bear that did occur in the wild... All of these animals come from common ancestors if you go back far enough and it makes you wonder just how freely genes could be traded back and forth with the right technology and a proper understanding of genetics.
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I think you need to look up what "law" means in a scientific context. The only "Law" of gravity I'm familiar with is Newton's Law of Gravity, which is known to be inaccurate and has been supplanted (at the theoretical if not all practical levels) by Einstein's Theory of Relativity. So tell me how a law is something more than a theory again?
The scientific community is completely open to other explanations that have actual evidence behind them. Debate about evolution happens all the time, and is ongoing as further evidence is accumulated. Now if you mean that science hasn't embraced whatever non-evolutionary theory you think is being neglected, well that's probably because outside of some blogs there's little to no evidence for it. We've watched evolution* happen in controlled environments. If you've got anything resembling the tiniest fraction of the evidence for evolution, your theory would be considered. If it had as much evidence as evolution, you'd up-end biology (much like evolutionary theory up-ended it).
Lastly, am I supposed to be shocked or dismayed that a textbook contained an error? Scientific knowledge advances, things previously held to be true are corrected, and freshmen-level textbooks often lag behind. And is your argument really that a false "missing link" means that humans (as opposed to all the other life forms on the planet) didn't undergo evolution? That's not the "proof". It's a step in the family tree. Just because you incorrectly identified your grandmother does not mean you have no family tree.
* Deliberate trap for the "Well sure microevolution is observed fact, but that doesn't mean anything about macro" response. Feel free not to take the bait.
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"Just" a shift in population ratios? Nice attempt to drive a wedge into the non-existent space between "micro-evolution" and "macro-evolution".
For the record:
Shift in population ratios = change in allele frequencies = evolution.
The most rabid believers in American Exceptionalism are the exact same people whose policies are destroying it.
It only seems to contradict global warming if you have only a superficial understanding of it. "Monotonic increase of temperature" was never a theory of global warming, so because a piece of data contradicts your understanding means nothing.
Also, the moth thing is more an example of natural selection than the evolution of a new trait. We've observed evolution in labs with flies and plants. Again, just because a layman's example and understanding doesn't seem to completely explain the theory, that doesn't mean that's all the understanding or explanation possible.
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You quoted from a non-scientific dictionary. Theory is misunderstood by people like you. In the context of science:
1. You make observations.
2. You make a hypothesis based on your observations.
3. You test you hypothesis to see if it holds its ground.
4. If the hypothesis survives the tests, it becomes a theory, if not it's back to square one.
Maximum likelihood phylogram constructed from analysis of up to 421 nucleotide sites of b-fibrinogen introns 5 and 7 combined. At nodes are Bayesian posterior probabilities and ML bootstrap values (100 repetitions).
There are two kind of people in the world...the kind that thinks the new Day the Earth Stood Still is science fiction, and the kind that thinks it would have been if Klaatu had said to Barnhardt something like that.
Equine Mammals Are Considerably Smaller
The Law of Gravitation and the Theory of Gravity are two related but different things.
The Law of Gravitation is (like most laws) is an equation describing the effect of gravity and nothing else.
The Theory of Gravity goes over gravities existence (or not) and how it actually works.
Theories can never become Laws (and Laws were never Theories) because they are two fundamentally different concepts within science.
the moth thing in England was brought up, even though I'm pretty certain everyone agrees that no evolution occurred there, it was just a shift in population ratios
"A shift in population ratios" is evolution by definition. Look it up.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
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Thank you for making this post. It's good to see that someone out there understands this basic concept. Although, as a sister post notes, we do have a pretty good idea as to the cause of gravity.
Law of gravity: Objects attract each other according to their mass and the square of the distance between them. (F = GMm/R^2)
Theory of gravity: Gravity is caused by the interaction of gravitons at the quantum level, making gravity one of the basic forces.
Notice that theories describe the how and why of things, laws make concrete facts about the way things are.
Neither scientific laws or scientific theories (not to be confused with traffic laws or layman's theories, which describe different things entirely) are above being revised. In the case of laws, becoming more precise as our instruments become more precise, for instance, I believe that the universal gravitational constant (G, above) has been changed at various times as we are able to get better measurements. Theories, are often refined, partially revised, or scrapped altogether, often, we will use different theories depending on the model we are using (once again, scientific model, not like a car model, or like a car in general, get your analogies away from me! ;-) ).
The most important distinction between laws and theories, is that laws can be proven: measure the gravitational pull between two masses, if it fits the formula, voila! Gravity still works as predicted, the aprocralypse is not upon us yet. Theories, however, can only be disproven, you can say, "Gravitons cannot be the cause of gravity, here is my evidence, which the theory doesn't explain," but you cannot say, "Here is my proof that gravitons cause gravity." (you can try to get proof, but at most you will have a very strong correlation, which, as every slashdotter is fond of pointing out, does not prove causation.
"But," you say, "that means that everything we know could be a lie!" To which I reply, "Yes, yes it does, but that is unlikely, because most theories that actually have a name, have been shown to correlate with the facts very, very consistently, and although this doesn't prove causation, it's a pretty good indication that most of science is true."
The creator of this post (Jacob Smith) hereby releases it, and all of his other posts, into the public domain.
AC cowardly says...
This, of course, is why most things ending in *ology aren't real science.
I'd be very curious to know how you managed to decide that from an article and a comment about taxONOMY (i.e. the study and method of naming the taxa)...
"Empathise with stupidity, and you're halfway to thinking like an idiot." - Iain M. Banks
When your theory is defined such that it includes both sides of interpretation of any given piece of data, it is hard to argue against. (e.g., I heard on the news that it was getting colder and certain ice caps or something were growing, not shrinking, and that that is "exactly what is expected with global warming, because with something like global warming, the unexpected is going to occur."
If that is actually what the "scientist" said, that is indeed moronic. Can you provide a reference? What do you mean by "the news"? Sounds more like some anti-global-warming moron trying to create a straw man.
OTOH, last I looked, there were good (ie. they have made accurate predictions) climate models that predict increasing average global temperatures while simultaneously predicting cooling around the poles. This is good science: show that your model fits some data and then try to understand what's going on. If your model does not make correct predictions (give it (today-n) years of data, and see if it can predict the last n years correctly), you need to change your model. That is exactly what science is.
Evolution is harder, since the physics is infinitely more complex--there are no precise predictive models of evolution in the physics sense, so whatever we see has to be incorporated into the theory without predictive testing. Evolution is thus more useful as a series of observations and a way of explaining them, rather than a proof in any mathematical sense. That doesn't make it wrong.
Elementary evolution theory does make a claim like "All complex life evolved from simpler life." If you now find a fossil of something complex that has no simpler ancestors, then evolution is wrong. Not that you can easily prove the bit about ancestors, but you get the idea. Finding that some complex life has simpler ancestors doesn't prove evolution, but it certainly makes it more plausible. Excuse the very shallow example, but you get the point.
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