The Evolutionary Hotseat

[Chuck]

[Thok]

[Elethiomel]

[extro...*]

[Chuck]

[Jedo the Jedi]

I was pondering the world the other day, and I was trying to do so from an evolutionary perspective when I realized that I don't know enough about it. These questions may have been answered elsewhere in here, but I'm lazy.

I understand that one of the guiding principles (or perhaps the guiding principle) of evolution is that a species mutates randomly, and the qualities which are the most beneficial remain and evolve the species while the not useful qualities die out. So...

- How did a single-celled organism evolve beyond that? Perhaps more pointedly, why? What makes more cells more beneficial to a previously single-celled organism? (I can imagine an answer of my own, but I would like an "evolutionist's" articulation.)
- Where did plants come from? What was the reason for their evolution?
- How did sentience evolve? I mean, if everything started from this single-celled organism and diverged at some point to make plants and animals, why did some animals evolve sentience while plants didn't?

Those are my starters. If it's already been answered, maybe point me to the page? If the questions seem as though they are born out of ignorance...they are. They are honest questions, and while I'm a skeptic of some evolutionary principles, these are truly seeking to understand better the theory of evolution. (It's still a theory, right?)
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[Thok]

One quick side note: don't think of evolution in terms of "survival of the fittest". A much more realistic way is "Genetics is written by those that survive and breed". (The point being that there is no well defined notion of "fittest", but surviving to breed is a well-defined notion. And it allows for a useful comparison to the phrase "History is written by the winners"; alternative specimens may have had strengths, but ultimately didn't breed.)

For each of the suggestions you've mentioned, there are obvious reasons why things that suddenly had those abilities might find it easier to survive and breed. And other things may have just never gotten those abilities; that's luck of the draw.

[Zag]

This is, of course, speculation, but it's informed speculation.

The first "life" was probably prokaryotes

[Jedo the Jedi]

That's a helpful distinction, Thok, though I already knew that "survival of the fittest" was an out-moded methodology for evolution.

Okay, Zag, so where was the divergence of plants and animals? I just don't see that. Another random permutation that a certain breed developed that the others didn't?

Also, where did sentience enter? Do plants have a low-level sentience that we don't know about?

And are there certain mutations which we can talk about never occurring because there's no predisposition of sorts? For example humans growing wings. (Though of course, Marvel Comics would disagree.)
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[Zag]

The mutation creating plants was already mentioned -- the initial chloroplasts (which create chlorophyll). Those are plants, and have their own, separate evolution.

We're still a humongous way from sentience. I'll try to hit the highlights:

Flexible, tubular structures are superior (i.e. more likely to survive and reproduce, in certain conditions) than spongy ones.

Tubular structures that constrict in waves, pushing the high-nutrient water through them, are superior to those that can't. They can grow much bigger, farther from the nutrient source. There isn't much of a leap from these colonies of independent cells which happen just to be connected by their adhesive membranes, to those structures starting to include specialized regions. One group forms a pocket which captures some body that is potentially nutrient rich, but takes longer to break down (possibly it is some of the chloroplast-containing cells which have formed their own membrane structure protecting them from earlier versions of such attacks). The cell which tend to create such pockets succeed, as long as there is a mechanism by which they squeeze the super-nutritious results of the break-down to the rest of the structure.

These structures of mildly-specialized, well-rooted tubular structures continue to grow and change. Lots of them break off, and most of these die. However, eventually some have morphed their constricting into actual locomotion, and they divert themselves back to the high-nutrient area. It's still a mistake to think about them doing this "on purpose." It's just that their "muscles" somehow are triggered by a difference in the amount of nutrients, such that they tend to move the object towards them. Of course, for this to work, there needs to be some mechanism by which the difference is detected, and it causes a signal which makes the right part of it squeeze, or wiggle, or whatever. Some versions of this free-moving animal develop different actions when different nutrients are "detected" and, lo, an olfactory system is born.

Diversity flourishes. lots of different systems appear as these structures of not-quite-independent cells develop more specialized sections. Different structures for protection (hard shell), locomotion (tentacles), digestion, respiration, assorted detection (touch, light, sound waves) arise, and we haven't even formed anything more complicated than a worm or a mollusk. Sexual reproduction comes about, which allows for more reliable reproduction of a complex structure without completely stagnating mutation.

Soon come arthropods -- crabs and lobsters -- with a primitive, chemical-based nervous system, with tubes that deliver the chemicals to run, to grab, to pull, etc. to the right muscles. These are replaced by electricity-based systems that work much better, and a hard shell forms around the critical bundle of "nerves" to protect it. This shell is made of similar structure to the outer shell, but with bands of an elastic version of it holding it together, making it tough but flexible. There are your vertebrates.

Another huge round of diversity, and you have vertebrates eating each other, since another creature similar to yourself is always a good way to get lots of the kind of amino acids you need.

The ability for like creatures to communicate spontaneously generates in a number of branches. The ants that can mark the way to the big food source with trail of pheromones that other ants follow tend to reproduce way faster than the insects that just go around on their own. Bees come up with better ways to communicate. Some predator fish succeed because they cooperate in cornering prey.

Amphibians become reptiles. Reptiles become birds, and their brains increase significantly. (The ones that didn't couldn't fly.) Another, new type of brain appears with mammals, and the level of ability to communicate increase impressively. Wolves hunt in packs where each member has a specific role to play, one that has to be learned from another wolf. The ones that do it well, whose members can learn quickly and effectively, reproduce more than the ones who don't. The creatures which are preyed upon also develop communications to warn each other of predators, and pretty soon the stupider predators are gone.

Some creatures escape the big predators in the trees. Their ability to calculate the complex geometry required to swing through trees increases quickly, because the ones that don't have the ability tend to die before reproducing. What they have to learn to survive is too much for a creature to be born with -- it must be learned from a parent. This means that child-rearing is a complex process and involves an entire tribal social structure. Are we at sentience, yet? I don't know. The communications just to establish social position without causing severe injury becomes more complex, with vocalizations that are more significant than just a growl or a whine.

Creatures have different identities in different roles -- family, tribe, etc. They are aware of the dominance of bigger gorillas and they wish they could take over and be the one to mate with all the females. (Not all of them, of course. Some don't care. Their genes don't make it into the next generation.) This awareness of position includes an awareness of self. A self-evaluation is necessary to decide when to be submissive and when it might be time to challenge the silverback for leadership. Is this sentience, yet? I think so.

[Jedo the Jedi]

One group evolves a tail of sorts to propel themselves through the water, and another simultaneously evolves a way to wriggle its way through the water? And they aren't necessarily in direct competition with one another?

And how does a proto-arthropod feed if no other similar thing has evolved? If these things don't progress close enough together in time (much less in space), how does a certain entity survive long enough to have its evolution continue for generations?

How long is each stage of this process thought to have taken? Was man the last evolutionary leap? If these things happen quasi-independently (within the different species), why have we not seen more evolutions taking place among the different categories...or have we?

And again, are there certain mutations we can say will never occur because there's no need for it in an evolutionary sense, despite mutations being mostly random?

(By the way, I expected you would be the one to answer all these questions, Zag, and I'm thankful. For some reason I trust your judgment/knowledge to pass on good information.)
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[Thok]

[Zag]

It doesn't matter that they are in competition. It's a big world. The huge leap was chlorophyll, which allowed the plants to live away from the nutrient-rich heat vents in the ocean. Once that happened, the bacteria which could consume the algae also could move away. Over the whole world, there is plenty of room for the billions of tiny mutations to form, die out, or live on.

Any improvement in any of dozens of avenues spreads quickly, changing the environment for everything else. It isn't a tiny system where one superior model wipes out the inferior models, and it is too simplistic to think just in concepts of inferior/superior, anyway. Mice are inferior to most other mammals in most ways, but they've specialized in one thing: They can out-breed all of them. So it doesn't matter that tons of predators make a living eating mice. The tiny rodents, with their copious reproduction, can stay ahead.

So how does a proto-arthropod feed? Well, the first exoskeletons might have been an improvement in keeping from being fed upon, or in locomotion, or something else, and it didn't really change what it fed upon -- I don't really know. Changes are really much smaller, not squid to lobster, but some tiny thing that provided a small advantage. Sometimes they are changes that simply didn't provide a disadvantage, so they hung around, but then another change combined with them and together it was a huge advantage. A shell over the tubules made them break off less, so they could grow longer. But this limited the creatures ability to reproduce, so it was a plus and a minus. Multiple types existed for a long time, perhaps interbreeding, perhaps eating each other. We can only speculate, but it's not to hard to spin up a story to explain any one concept.

Humans certainly weren't the last mutation. There are new species every day. It's been observed that the different facial mites that live on each large mammal (like you and me, for instance) are probably different species -- technically -- from each other. There was recently a successful experiment in evolution which showed how some evolutionary leaps that really need two changes in concert can be made. I learned about it here on GL, so it's probably in this thread. It's something like 3 years ago, but I'll summarize it later today if I can find the time.

[Zag]

[Jedo the Jedi]

Yes, small things like bacteria and viruses evolve every year in response to the medicines we use, but it doesn't seem like any of them are becoming something new. Shouldn't all things be advancing to a next evolutionary stage? I don't want to talk about humans being the pinnacle of evolution (we suck in a lot of areas), but we're obviously more adaptable and able to manipulate our environment. Isn't this something more animals should be evolving toward or are they already and we just have to wait a billion years to see it?
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[Thok]

[Jedo the Jedi]

I get that, but are mice going to stop with their extreme breeding ability? Is there not going to be another evolutionary leap making them better? Or that's the point: they are experiencing lots of evolutionary traits which aren't taking hold because they aren't furthering the species or it's some latent ability which will only surface when combined with something else later.
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[Zag]

You're still thinking about this as if it is an intentional thing, as if there's an ultimate goal. There isn't -- it is just "what's successful enough in the current environment to reproduce?"

Are mice going to evolve to some next step? Sure. They have, lots of times. Some mice (or an earlier version of them) have evolved to be better at climbing trees, and their gnawing teeth turned into something better for eating nuts. We call those squirrels today. It doesn't mean that all the mice changed overnight -- one family developed these other traits, moved into an otherwise-unoccupied ecological niche, and thrived. All their cousins who hadn't evolved continued to survive and breed.

A lot of those tree-dwelling rodents succumbed to predators which could climb trees, sometimes getting eaten, sometimes dying in a fall as they tried to get away, but one random mutant's skin was deformed, attached from well down on his legs to his body. It would seem a survival handicap, making running more awkward, but it didn't seem to hamper him too much. However, when one of the predators chased him and he made the leap that, for so many of his distant cousins, was to death, he happened to open his legs wide and he glided to another tree. He passed this along to his children, who interbred and expanded it, and there were flying squirrels. It doesn't mean that the existing squirrels died out -- they still had their own advantages.

Some flying squirrels became bats who carried on a arms race with the moths. Arms races are a pretty common thing in evolution, where predator and prey evolve together, each developing some trait that overcomes a strength in the other. In these cases, the older models do die out, because the opponent eats them all, or because the opponent who failed to improve starves to death. In the bats and moths, the early moths had evolved to fly about only at dusk and dawn, when there was enough light for them but not enough for their predators, the birds, to fly safely. The bats with big ears who could hear the noisily-flying moths could hunt them by sound and they thrived. The moths with sound dampeners on their wings didn't get eaten until bats turned up with even better hearing, etc. The cycle continued until moths flew almost silently, and bats had hearing that was vastly better than any other creature.

I saw a show about a similar arms race that created the poisonous frogs in South America and the snakes that eat them. No other creature could even think of eating those frogs today except for that one breed of snake that has acquired the ability to withstand the poison.

[novice]

[Jedo the Jedi]

Does it only take one example of the mutation to pass it on?

So, some part of a group evolves an anomaly. If the anomaly aids in survival, it's more likely to stick around (the flying squirrel), but if it simply doesn't hamper the creature, the anomaly might pass on or simply die out? In the meantime, the other squirrels who have trouble getting away might evolve to be better runners through the treetops, so both survive?

That makes some sense. Part of what I'm grasping toward is why don't we see species making the leap from flying squirrel to bat today or why don't we see the in-between stage? If we do, what is the example? It seems to me this happened a lot in history based on what you are telling me, but this type of evolution doesn't seem so prevalent any more.

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Slightly unrelated, I'm just going to throw out something. Looking simply at humanity, what has been the evolution over time? I imagine you would say we learned better techniques regarding tools and their uses for hunting and agriculture, we became progressively less hairy, and our aesthetic sensibilities developed. Probably you would say there was a change in our brains, either in their capacity or in the development of certain sections.

Going back maybe 5,000 years, we see societies really developing, and we can see early thinkers emerging. Would you call it evolution getting from Pythagoras to Mandelbrot? It seems not so much that one was necessarily more capable of thought than the other, but that the latter had a greater body of information on which to stand. Similarly, our more advanced technology and our ability to produce it doesn't seem related to the evolution in our thinking but to building on the ideas of those who came before. Is that correct?
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[Jedo the Jedi]

Thanks, novice. That simulpost is illuminating.

There are thousands of animals on the endangered species list. Are these animals exhibiting evolutionary traits to help them survive, or is human interaction which attempts to save them with outside help hampering their "need to evolve"?

If we had a nuclear holocaust/apocalypse, we would likely see significant evolutionary changes?
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[itisally]

In regards to humans. We have over time gotten larger. And not just because of the rise in obesity. The average height has increased significantly over the last 200 years and continues to do so.
Here is an artical about it. http://www.scientificamerican.com/article.cfm?id=why-are-we-getting-taller

An interesting related fact is that birth weights and head circumferences have also increased. This has not been met with an increase in the pelvic cavity of women and some speculate that this has influenced the need of medical interventions like C-sections in child birth.

In this case our mental ability to solve the challenge overcomes what would happen in other species. That being, if a mothers hips were too narrow, both she and child would die in child birth and those genes (large head, narrow birth canal) would not be passed on. Only those families with larger birth canals or smaller heads would survive.
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I could agree with you, but then we would both be wrong.

[novice]

[Jedo the Jedi]

Considering the discussion...
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[Zag]

[Zag]

SciShow is terrific, and this is one of their better ones, dealing with human evolution.

http://www.youtube.com/watch?v=ROwKq3kxPEA

[Chuck]

[Zag]

Pat Robertson speaks out AGAINST creationism!

Finally, a high-profile Christian leader with an actual brain in his head. Of course, his reasoning is that he'll lose the young people (and, no doubt, all their donations) if the church doesn't embrace science, though that might only be my cynicism talking.

What I looked for and couldn't find, but I'd really like SOME Christian leader to say is something along these lines: "Of course the Bible is the true word of God, but God often speaks to us in metaphors. This is one case. God gave us eyes to see and a brain to think, and it is wrong of us not to use them."

[Jedo the Jedi]

[Zag]

[Jedo the Jedi]

[Zag]

[Jedo the Jedi]

I live in the South, and my tradition is closely related to Southern Baptists. Believe me, I'm familiar. They are some of the ones with whom I take issue. The problem there is they have their own, inbred schools which just create a cycle, so I'm not sure there is much hope there. I mean, there are plenty who branch out and come back and cause change, but they are still a minority. So I'm aware that there are a lot of moronic church leaders out there.

The Genesis story is about how the world was made, technically, but my point is it isn't some sort of scientific focus or proposal of doctrine for the creation of the world. Genesis was probably written no earlier than 8th Century B.C.E., so how much weight of accuracy (even for ancient standards) can it have? Besides that, Biblical authors were writing for different reasons than our modern notions of "historical accuracy."

In the end, it definitely is news precisely because not many Christian leaders support the view of Robertson. Maybe he will be the first of many.
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[Chuck]