btt
Evidence for evolution, Installment 7: The Panda's Thumb
by seattleniceguy 21 Replies latest jw friends
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seattleniceguy
btt for my readers who might not yet have noticed this thread
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drwtsn32
Thanks SNG!
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Pole
Interesting and makes sense on the whole.
This is a very good example of evolution in action because it showcases several key aspects of evolution:
- The design is not "good" by any definition of the word. It is a jury-rigged system that used what was available to the advantage of the panda.
- By co-opting existing features and slowly adapting them to another purpose, evolutionary forces have introduced a new biological feature (a new appendage).
I have no problem accepting one-step at a time evolution.
At the same time, I think evolutionary theory in the forms I've seen has to depend on a very poor metaphysics (one-link cause-effect relationships) which is very difficult to accept in certain cases. Such as certain species of animals pretending to drop dead when in danger and even emitting a carrion-like smell to discourage other species from eating them. It makes perfect sense for the human observer, but how much sense does it make in terms of the mechanics of the evolution? Or flies pretending to be wasps. I saw one of those last summer. It has a yellow thorax with black stripes but no sting. So, although it was harmless, it took me a while to figure out it was a fly and not a wasp. One almost has to personify evolution to explain that.
Now, as a layman in the field I'd like to have this explained in one of your installements, SNG.
Pole
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seattleniceguy
Hello Pole,
Those aren't too difficult to explain. Actually, those are some of the most readily understandable from a one-step-process point of view.
Let's say a group of flies lives in the same area as a group of wasps. Their primary predator is a frog who finds the flies to be a delectable treat. The frogs avoid eating the wasps for obvious reasons, having learned the painful consequences early on. For flies living in this area, it is an obvious selective advantage to look something like a wasp, if at all possible.
Now, obviously, flies don't just suddenly start hatching looking like wasps. But perhaps there is a range of color possible for this population of flies. Some of the flies have little spots of yellow on them. Surely they wouldn't fool anyone who looked at them carefully, but perhaps their predators are momentarily confused or cautious and so avoid eating them some of the time. This instantly reinforces the yellow-spotted fly trait because those flies are now surviving better.
If the selective advantage continues for flies that look at least something like wasps, then it's only a matter of time before the trait is strongly reinforced into the population. Remember, they don't have to fool all of the frogs all of the time, they only need to fool some of the frogs some of the time. It only has to be enough subterfuge to provide some real amount of survival advantage. Even if, say, the yellow spot brings the rate of predation downby only 10% - tricking only the stupid frogs - there is still a very real survival advantage to the trait. Hey, not getting eaten by a stupid frog is still not getting eaten. So at this stage, the initial version of the camoflage can be very poor but still work.
Once the subterfuge has been established in the population, then competition among the flies themselves will hone the trait. After all, now there are a lot of flies flying around with yellow spots on them. The frogs have to eat something, so they start taking risks with the ones that look the least like wasps. In this way, the ones that look more like wasps have a survival advantage.
This is an interesting example, because it illustrates how both intra-species and extra-species pressure can introduce and hone new traits. The frogs applied the pressure to look like wasps, but intra-species competition among the wasps applied pressure to look more and more like a wasp.
Does that answer your question at all? I was just reading about new traits that appeared in E. coli after something like 2000 generations. I'll see if I can find something concise on that for my next article.
SNG
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Pole
SNG,
Does that answer your question at all? I was just reading about new traits that appeared in E. coli after something like 2000 generations. I'll see if I can find something concise on that for my next article.
Thanks for an exhaustive answer. Yes, it does make sense to me as long as I accept a set of assumptions (which I have to for lack of a better answer). Such as random spots gradually becoming regular wasp-likes stripes due to to the fact that they allow the flies to survive better. The thing is though that over here wasp-like flies are much rarer than "normal" flies that typically fall prey to frogs. But from what I understand, you are saying that there may have occurred a niche environment in which looking more like a wasp gave the fly a competitive edge (for instance in swampy areas inhabited by frogs). That would make sense.
So maybe the fault is with my reasoning. When I read facts such as:
"The Virginia opossum rolls over and lies still with its mouth open and a glassy look in its eyes"
or
"The hog nosed snake also pretends to be dead and may even give off a rotting smell. Before it resorts to this, however, it mimics a rattlesnake, raising its head as if about to strike and making a rattling sound."
(http://ladywildlife.com/animal/howmimicryprotectsanimals.html)
I tend to think there must be a metaphysics that acounts for it. I find it demanding to think there must have been a random mutation in a bunch of chicken-shit hog-nosed snakes which made them drop unconscious and smell bad when facing an enemy. And that this weakness of character turned out to be advantageous especially when used in tandem with pretending to be a rattle snake before fainting.
But as I said when I take a few assumptions for granted I can see how what I call mimicry may have been caused by a series of "random" factors. After all biological randomness is not mathematical randomness.
Thanks again, your reply got me thinking.
Pole
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seattleniceguy
But from what I understand, you are saying that there may have occurred a niche environment in which looking more like a wasp gave the fly a competitive edge (for instance in swampy areas inhabited by frogs).
Exactly. This type of evolution could only occur in such an environment. Now, here's another interesting consequence of that fact. Let's say the wasp lookalikes evolve in a niche environment, but the primary predator (the frog) that caused the selective advantage does not exist elsewhere. Maybe outside of the pond, it is a selective disadvantage to look like a wasp because a particular bird loves to eat wasps. In this case, the wasp lookalike will not compete well against the "normal" flies in that environment, and so will stay in the minority.
But let's say that a small population of these lookalike flies happens upon a new pond with a similar ecosystem, which is inhabited only by the "normal" flies. In this case, they might take the pond by storm, as it were. In competition for resources, the non-lookalike flies would be decimated and the lookalikes would take control in a very short span of time. If this scenario played out many times in ponds throughout the area, later observers would see a strange record in which the lookalike flies appear to have evolved overnight. Of course, the flies did not actually evolve overnight, but were taken over overnight by a form that evolved gradually in a niche environment. It is believed that this scenario happens frequently.
With regard to the animals that play dead or emit strange odors, again, it would be a mistake to think that a creature suddenly started doing this because he thought it was a good idea. Playing dead especially is one of those mechanisms that works sometimes but not others. Imagine the opposum finds itself exposed to a new predator that doesn't give a damn whether it looks dead or not. Now playing dead is just plain stupid, and the opposums that play dead instead of running away will soon be gobbled up, putting strong pressure on the ones that don't play dead, which were previously considered to be defective.
The main thing to keep in mind when considering imitative features is that the first step only had to provide marginal benefit. It didn't have to jump to a fully-formed carrion stench, for example. It just had to be stinky enough that some of the predators decided to pass on the meal.
Glad you brought this stuff up. It's quite interesting.
SNG
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stillajwexelder
Thankyou again - the question is "Were there any Pandas on Noahs Ark and did he and his family provide fresh bamboo shoots for them
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seattleniceguy
LOL @ stilla...
84 pounds of bamboo a day for two pandas for a year would be:
84 x 2 x 365 = 61320 pounds or over 30 tons of bamboo! And what about the bamboo they'd need to eat until new growth was established on the freshly wiped earth? :-) Glad I'm not still trying to rationalize that.
SNG
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hooberus
The publication: Noah's Ark: a Feasibility Study by biologist John Woodmorappe provides detailed calculates of food requirements and ark capacity (as well as answers common "anti ark" arguments).
available from http://www.answersingenesis.org
(go to technical section of bookstore)
Noah's Ark: A Feasibility Study John Woodmorappe #10-3-078