Questions about Evolution

Thoth

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Hello all. I had some questions about evolution and was hoping someone here could answer them. First off, I know this can be a sensitive topic, but I'm asking these questions out of curiosity. I'm pretty sure I understand the basics of evolution, but I must admit, my school was a bit lacking since I was placed in a basic biology class. Apparently I was too distracting for the "smart" kids so I was placed with the other delinquents :rolleyes: thanks public school system! Anyways, on to the questions:

I'm not sure I understand exactly what causes certain species to adapt rather unique traits. Such as some of the albino shrimp, crayfish, and fish found in certain subterranean rivers and lakes. What exactly causes them to "change" this color? Was it truly a situation where a whole load of them lived in this cave, with only the mutant albino ones surviving? Why would they survive though? What exactly is gained from albinism other then the fact that pigmentation is not needed in a dark environment? What exactly caused this to occur and was it gradual, meaning did the pigmentation slowly recede until it reached its current state? Why would this happen? Do scientists know why organs that are not needed, simply recede until gone?

I suppose the same question applies to why certain animals have diminutive eyes. Or, with us the question of the appendix. Is it being somehow phased out seeing as how it apparently causes more harm then good in many people? Apparently, it once helped filter bacteria, which would make sense for early humans that would have eaten dirty or raw food. What exactly causes such an organ to slowly lose its use? Simply because it's not used anymore?

My final question is this: If a group of humans, let's say 50 males and 50 females, all unrelated, were to enter a large cave system with an abundance of food: Let's say some sort of fungi and small animals or something. Let's also say that the danger of falling into chasms and other such environmental hazards are minimal and that the population would avoid population bottlenecks and incest thus ensuring their survival. Can we predict what would eventually happen to these people? Would their pigmentation fade? Would their vision get weaker as well? Again, what drives this? It would seem as though one could have good vision even though it is dark. Why would it fade away?

Anyways, that's all for now. Thanks in advance to any responses!
 
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I'll take a shot at answering a couple of these questions.
Do scientists know why organs that are not needed, simply recede until gone?
Those organs are merely complying with the collective will of the species. The members don't all get together and vote on it obviously (that would be ludicrous). Those decisions are made by leaders who are typically choosen via peridically-held free elections.

What exactly causes such an organ to slowly lose its use? Simply because it's not used anymore?
That's correct. Once the decision to evolve them away is reached by those in power, their days are then numbered.

End of daily use is the first step, followed by reduced amounts of incoming phone calls, emails and letters, until they are eventually forgotten altogether. At that point they just wither up and disappear (though some believe in life after natural selection).

Dissension rarely occurs as it's always dealt with harshly. For instance clams who refused to let their legs wither away were kicked to death by the others; pigs who weren't willing to sacrifice their wings were chocked with feathers, and dinosaurs who were unwilling to give up eating meat were put on a diet of McDonalds hamburgers until they complied.

Nature can be very strict.
 
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I'll take a shot at answering a couple of these questions.Those organs are merely complying with the collective will of the species. The members don't all get together and vote on it obviously (that would be ludicrous). Those decisions are made by leaders who are typically choosen via peridically-held free elections.

So, if I want a sixth finger and the ability to spit acid, I should support a leader that also wants these things? I can't simply vote for these features? That seems unfair...

That's correct. Once the decision to evolve them away is reached by those in power, their days are then numbered.

I'd like to do away with lactose-intolerance.

End of daily use is the first step, followed by reduced amounts of incoming phone calls, emails and letters, until they are eventually forgotten altogether. At that point they just wither up and disappear (though some believe in life after natural selection).

So, if we want to speed this process along, we should put them on a national do not call list?

Dissension rarely occurs as it's always dealt with harshly. For instance clams who refused to let their legs wither away were kicked to death by the others; pigs who weren't willing to sacrifice their wings were chocked with feathers, and dinosaurs who were unwilling to give up eating meat were put on a diet of McDonalds hamburgers until they complied.

According to Jurassic Park, only Raptors could open doors, how do you explain the rest of them even getting inside McDonalds? It doesn't make sense.

Nature can be very strict.

Indeed.
 
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I'm not sure I understand exactly what causes certain species to adapt rather unique traits. Such as some of the albino shrimp, crayfish, and fish found in certain subterranean rivers and lakes. What exactly causes them to "change" this color? Was it truly a situation where a whole load of them lived in this cave, with only the mutant albino ones surviving? Why would they survive though? What exactly is gained from albinism other then the fact that pigmentation is not needed in a dark environment? What exactly caused this to occur and was it gradual, meaning did the pigmentation slowly recede until it reached its current state? Why would this happen? Do scientists know why organs that are not needed, simply recede until gone?

Simply put, it's the "no free lunch" principle.

It takes resources -- food, metabolic, whatever -- to produce features such as pigment or organs. That means that if a feature is no longer useful, an individual that lacks the feature, or has a slightly atrophied version of the feature, has a slight survival advantage over one that has the complete feature, because it's not using scarce resources to produce that feature. It might be able to survive with slightly less food, or reach maturity slightly earlier, or be slightly more powerful compared to its weight, or whatever. So the mutation is beneficial and propagates.

A related reason is that things are interconnected in complex ways. Mutations or gene combinations may do more than one thing. So, for example, an "albino" mutation might simultaneously make cellular metabolism in the skin more efficient. Above ground, the disadvantages of being albino outweigh the advantages of better metabolism, so the mutation doesn't propagate. Underground, there's no penalty for being albino, but there's a reward for having better metabolism, so it does.

Given enough time, this means that underground creatures will tend to lose their pigmentation, vision, and other surface-adaptive traits.

I suppose the same question applies to why certain animals have diminutive eyes. Or, with us the question of the appendix. Is it being somehow phased out seeing as how it apparently causes more harm then good in many people? Apparently, it once helped filter bacteria, which would make sense for early humans that would have eaten dirty or raw food. What exactly causes such an organ to slowly lose its use? Simply because it's not used anymore?

Could be anything, really -- changes in diet, changes in the environment, mutations elsewhere that do the same job better. Interestingly, though, it seems like the human appendix has reached something of a "stable state." The reason is that if it gets smaller than it is now, it gets more prone to infection; if it gets bigger, it consumes more resources. IOW, unless there's a mutation that suddenly completely gets rid of it (which, I understand, is unlikely, if the appendix is a product of more than one gene, which is almost certain), it's here to stay.

My final question is this: If a group of humans, let's say 50 males and 50 females, all unrelated, were to enter a large cave system with an abundance of food: Let's say some sort of fungi and small animals or something. Let's also say that the danger of falling into chasms and other such environmental hazards are minimal and that the population would avoid population bottlenecks and incest thus ensuring their survival. Can we predict what would eventually happen to these people? Would their pigmentation fade? Would their vision get weaker as well? Again, what drives this? It would seem as though one could have good vision even though it is dark. Why would it fade away?

Ah, this is actually a really interesting question, and the answer might surprise you. (We're assuming they don't use fire or any other sources of light, of course.)

The very first generation born and growing up in the cave will be completely blind, and will not develop vision if brought out of the cave as adults. (Should they have offspring outside the cave, though, the offspring will have normal vision.)

The reason is the way vision develops as babies grow up. It's "trained" -- that is, nerve cells in parts of the brain that deal with vision connect in response to stimuli from the eye. Absent such stimuli, the connections won't form, and the person won't be able to develop eyesight. The brains of people who are born blind end up physically different than brains of people born with eyesight. (The brain is also surprisingly good at repurposing itself -- for example, people born blind will use parts of their visual cortex that's normally used for "image processing" for other purposes, and will therefore appear to have uncanny ability at "sensing" things like the size and shape of spaces and the location and position of people within them. Their brains produce a 3D model of the space, only with a different data set.)

It will take hundreds of thousands or millions of years for the genes that enable eyesight to get flushed out of the system or deactivated, but because of pressures like the ones I described above, yes, eventually a genetically blind, albino human population would evolve. For a long time, there would be occasional throwbacks, but they'd never know the difference!
 
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Ah, this is actually a really interesting question, and the answer might surprise you. (We're assuming they don't use fire or any other sources of light, of course.)

The very first generation born and growing up in the cave will be completely blind, and will not develop vision if brought out of the cave as adults. (Should they have offspring outside the cave, though, the offspring will have normal vision.)

The reason is the way vision develops as babies grow up. It's "trained" -- that is, nerve cells in parts of the brain that deal with vision connect in response to stimuli from the eye. Absent such stimuli, the connections won't form, and the person won't be able to develop eyesight. The brains of people who are born blind end up physically different than brains of people born with eyesight. (The brain is also surprisingly good at repurposing itself -- for example, people born blind will use parts of their visual cortex that's normally used for "image processing" for other purposes, and will therefore appear to have uncanny ability at "sensing" things like the size and shape of spaces and the location and position of people within them. Their brains produce a 3D model of the space, only with a different data set.)

It will take hundreds of thousands or millions of years for the genes that enable eyesight to get flushed out of the system or deactivated, but because of pressures like the ones I described above, yes, eventually a genetically blind, albino human population would evolve. For a long time, there would be occasional throwbacks, but they'd never know the difference!

Thanks, this answered a lot for me. Your mention of children born and grown in the absence of light reminds me of a horrific story about some parents who had a baby girl and kept her tied to a chair, in a dimly lit room for most of her life. I think she was 10 or so when she was finally discovered. As terrible as it is, it was still rather interesting how this poor girls brain developed. She was terribly myopic, could barely walk, and was obviously socially broken. Her parents never talked to her. I can't remember her name, but I remember there being interesting studies from therapists and psychologists that were trying to help her.

Anyways, thanks for the info.
 
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I australia, I read, there's that big, huge frog causing havoc among natiuve animals, because it spreads insanely and eats EVERYTHING. And is poisonous, too.

I read that the newer ones of this frog species of it have longer hind legs than older generations did, and everyone assumes it is for better fleeing from predators.

No-one actually knows why this happened in so a relatively short time.

But everyone says it's relatively fast evolution.

This is how I understood it.
 
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First I've heard about it!!
 
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It's why bacteria will eventually win, if they haven't won already.
 
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