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Looking for evolution example

aggle-rithm

Ardent Formulist
aggle-rithm
Joined
Jun 9, 2005
Messages
15,334
Location
Austin, TX
Hello,

I'm trying to come up with a very specific example of an organic structure that meets the following criteria:

1. It's original "purpose" was different (for instance, arm/flipper).

2. It has not yet evolved sufficiently to be considered an optimal design.

A few things I have found come close. The humeral elevator in birds was a possibility, but I think it doesn't really qualify because it serves its current purpose so well (allowing a bird to take off from the ground). Also, the inner ear, although once a jaw structure, works pretty well considering it's original purpose.

Any ideas?
 
Would a human body part be any good to you? The coccyx in humans (and other Great Apes) is the remnant of a vestigial tail, but is still used as an attachment for various muscles and tendons. It is also important for taking weight when a human is sitting. It's original purpose was to support a tail, and it has not completely evolved to the loss of that function.
 
Well, part of the problem is, how do you define optimal? Is there ANY organ that couldn't be improved somehow?
 
aggle-rithm said:
Hello,

I'm trying to come up with a very specific example of an organic structure that meets the following criteria:

1. It's original "purpose" was different (for instance, arm/flipper).

2. It has not yet evolved sufficiently to be considered an optimal design.

A few things I have found come close. The humeral elevator in birds was a possibility, but I think it doesn't really qualify because it serves its current purpose so well (allowing a bird to take off from the ground). Also, the inner ear, although once a jaw structure, works pretty well considering it's original purpose.

Any ideas?
Click to expand...
Wings on penguins.
 
aggle-rithm said:
Hello,

I'm trying to come up with a very specific example of an organic structure that meets the following criteria:

1. It's original "purpose" was different (for instance, arm/flipper).

2. It has not yet evolved sufficiently to be considered an optimal design.

A few things I have found come close. The humeral elevator in birds was a possibility, but I think it doesn't really qualify because it serves its current purpose so well (allowing a bird to take off from the ground). Also, the inner ear, although once a jaw structure, works pretty well considering it's original purpose.

Any ideas?
Click to expand...

http://en.wikipedia.org/wiki/Otter
 
aggle-rithm said:
Hello,

I'm trying to come up with a very specific example of an organic structure that meets the following criteria:

1. It's original "purpose" was different (for instance, arm/flipper).

2. It has not yet evolved sufficiently to be considered an optimal design.

A few things I have found come close. The humeral elevator in birds was a possibility, but I think it doesn't really qualify because it serves its current purpose so well (allowing a bird to take off from the ground). Also, the inner ear, although once a jaw structure, works pretty well considering it's original purpose.

Any ideas?
Click to expand...

Whale hip bone, originally for legs, now just muscle attachments
mens nipples, in the womb started as the development for female breasts, in men, now just an erogenous zone
toes on human feet, started in evolution as grasping fingers, now used for balancing a biped while walking
;)
 
phunk said:
Well, part of the problem is, how do you define optimal? Is there ANY organ that couldn't be improved somehow?
Click to expand...

Optimal would be something that obviously contributes to survivability. Sub-optimal would be something that might provide net survivability, but in some ways hinders it.

Maybe a peacock's tail would work. It's original purpose was to provide stability in flight, but it now serves only as a mating display. Important enough that it wasn't eliminated by natural selection, but sort of a metaphorical ball and chain when it comes to escaping predators.
 
aggle-rithm said:
Maybe a peacock's tail would work. It's original purpose was to provide stability in flight, but it now serves only as a mating display. Important enough that it wasn't eliminated by natural selection, but sort of a metaphorical ball and chain when it comes to escaping predators.
Click to expand...

aggle, you've fallen into the trap of thinking that there is only one form of natural selection, what is sometimes referred to a "ecological selection". This is the selection for traits which improve survival in the usual sense. You know; disease resistance, predator avoidance, food gathering ability, etc.

There is another important variety of natural selection: sexual selection. Darwin actually paid a good deal of attention to this, but it's not often mentioned when discussing evolution. The peacock's tail is generally a great example of the two selection types working in opposite directions. It is, as you say, a "metaphorical ball and chain when it comes to escaping predators". Actually, it's not just the tail - it's the whole damn bird that draws the eye. However, it is apparent that peahens really dig flashy guys, so the trait lives on. Less gaudy versions presumably live longer, with the potential to reproduce more often, but they don't do as well in getting to mate in the first place.
 
WhatRoughBeast said:
aggle, you've fallen into the trap of thinking that there is only one form of natural selection, what is sometimes referred to a "ecological selection". This is the selection for traits which improve survival in the usual sense. You know; disease resistance, predator avoidance, food gathering ability, etc.
Click to expand...

I haven't overlooked the fact that the peacock's tail is an example of sexual selection. That's why I said it "might" work. Using that example might muddy the point I'm trying to make.

I think of sexual selection as being a subset of natural selection. The only thing that separates it from other inherited traits is that it is specific to sex.
 
1. It's original "purpose" was different (for instance, arm/flipper).
Click to expand...
Panda's thumb. "Canine" teeth in sloths. Teeth in general. All terrestrial vertebrate limbs, and all vertebrate jaws. Mammal ear bones. Lungs. The swimming leg on Xanthid crabs. The tail of crabs.

2. It has not yet evolved sufficiently to be considered an optimal design.
Click to expand...
Panda's thumb again. Human eyes. Human skeletons. Browsing behaviors of any number of organisms. Really, just look at any population that's expanding geographically and you'll find dozens of exmaples. Our own reliance on clothing and heating/cooling systems is an example of this--our bodys cannot handle the environment in Northern Europe, for example, without behavioral modifications.

Optimal would be something that obviously contributes to survivability. Sub-optimal would be something that might provide net survivability, but in some ways hinders it.
Click to expand...
Problem is, there are trade-offs. Something may appear suboptimal, but it may be the best option when the organism as a whole is considered. It's why I dislike the selfish gene idea--you can't atomize life to that extent, you've got to look at the creature as a whole to understand why evolution worked the way it did.
 
azzthom said:
Would a human body part be any good to you? The coccyx in humans (and other Great Apes) is the remnant of a vestigial tail, but is still used as an attachment for various muscles and tendons. It is also important for taking weight when a human is sitting. It's original purpose was to support a tail, and it has not completely evolved to the loss of that function.
Click to expand...

Stupid coccyx, prolonged weight on this region can cause Pilonidal Cysts in large amounts of the population. There's nothing like a painful swollen gland on the cleft of your buttocks.
 
I, too, do not understand requirement (2). When would we ever get an optimal design out of evolution?

The flagellum meets requirement (1). Is it an optimal design?

~~ Paul
 
I was going to say flagellum. Basically the creationist nutters used to make a big deal about how it could never have evolved. So someone did the research and it turns out that it did have intermediate useful stages that weren't motors.
 
aggle-rithm said:
Optimal would be something that obviously contributes to survivability. Sub-optimal would be something that might provide net survivability, but in some ways hinders it.

Maybe a peacock's tail would work. It's original purpose was to provide stability in flight, but it now serves only as a mating display. Important enough that it wasn't eliminated by natural selection, but sort of a metaphorical ball and chain when it comes to escaping predators.
Click to expand...
Peacock tails are often cited as an example where the mate's preference resulted in less male survival. The selection pressure sort of blew the hypothesis all these things the females liked indicated better health or something else related to survival thus explaining how the survival selection was working. Maybe not.
 
Pretty sure hair/fur would be an example, as it was useful only for sensing vibrations long before it was useful for warmth (and intimidation/threat display in some species).
 
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