How exactly does evolution work?

[Kathranis]

i get natural selection that the better adapted things breed better but what i didnt understand was how those better adapted things showed up in the first place

Random genetic mutation.

The same reason why someone might have hairy arms even though neither of their parents is hairy, or why one kid in a family might have big hands, or why every now and then a little girl is born with webbed toes, or why some kids are predisposed to heart disease.

Each time a new life begins, there's a chance for random mutation in its DNA. Some strands of DNA might be missing, or different, and that just randomly produces various effects. Anything could happen. They could have one less bone in each hand, or they could have a blood disorder, or their teeth could be bigger, or they could have bad eyesight, or longer legs, or their fingernails grow .01 mm faster.

If you're thinking about wilderness survival, some of those traits would be more useful than others.

[Deleted]

Animal uses head to headbutt things as defense/attack.

Skull hardens as result.

Generations and habits pass on.

The hardened skulls become harder, and eventually forms a layered nub

The layer nub generations later forms into a horn.

I doubt it's a conscious thing at all.

But, on the flipside, I'd REALLY like to know how Octopi evolve with Chromataphores. Not sure what the process is for that... same with Butterflies having eye spots on their wings. How did those develop? Was it purely a psychological knowledge and fear of eyes that perhaps subconsciously influenced a physical manifestation?

More like individuals where mutations resulted in a harder skull were more likely to survive in that scenario, so their mutated DNA gets passed on to the e next generation.

[Spectral]

Animal uses head to headbutt things as defense/attack.

Skull hardens as result.

Generations and habits pass on.

The hardened skulls become harder, and eventually forms a layered nub

The layer nub generations later forms into a horn.

I doubt it's a conscious thing at all.

But, on the flipside, I'd REALLY like to know how Octopi evolve with Chromataphores. Not sure what the process is for that... same with Butterflies having eye spots on their wings. How did those develop? Was it purely a psychological knowledge and fear of eyes that perhaps subconsciously influenced a physical manifestation?

This whole thing is Lamarckian. It is wrong (with the exception of epigenetics, which are kind of beside the point for general understanding).

[Deleted]

You were made by your mother and father, you are born with characteristics that they inherited. (You might have the same nose etc) Well, imagine if you were, I don't know, a bear, that wouldn't freeze to death in the cold like others do, because of the genes he was given in birth. That bear would have cubs, and those cubs would inherit the characteristic of surviving the cold, were as everyone else can't. Eventually, you have polar bears. The bear being able to survive the cold has 'mutated DNA' that has allowed him to adapt more efficiently to his surroundings then other bears.

P.s, I have no idea how polar bears evolved, but i'm just throwing that out there as an example.

[mafao]

As many people in this thread have correctly pointed out, mutations are just random changes in the DNA which get passed to the children. These mutation happens because DNA replication is not perfect. If the change is beneficially, it is more likely to get passed on. However, there is another important concept to it.

Evolution is often tied to a bottleneck situation. You need to have some sort of a closed environment/population so that the change can actually manifest itself. Imagine the following (hypothetical) situation: due to some cataclysmic change a part of land gets separated and becomes an island. Now, there are some birds living on this island. Few times per year, especially strong winds arise and the birds get swept into the ocean and can't ever return. Of course, these birds are massively in trouble - each time the windy season comes more and more of them die, in the end only a small amount remains. Now suppose that a 'cripple' bird is born, who can't fly. Because the island is free of predators, it can still move around just fine and catch some food (like worms). And because it can't fly, it never gets swept into the ocean, thus living long and producing lots of offspring. Some time passes and the subsequent generations of birds all are grand-children of the original cripple - thus a new flightless bird species is born.

Of course, this species will die very fast is some cats will find their way onto the island. Which has happened to many flightless species actually.

[Kathranis]

This is quite wrong; selective pressures on humans are different from what they were 50,000 years ago, but that doesn't mean they don't exist. There's actually a fair bit of evidence that changes to humans have sped up considerably. I recommend this book: http://www.amazon.com/000-Year-Explo.../dp/0465020429

Absolutely.

Even now, even with our technology and medicine, and our seeming ability to choose instead of letting nature choose for us, we're still evolving and adapting to the world around us, even as we build that world ourselves.

Right now, there's some fat little kid in Georgia who was born with a mutated heart, and while all the other fat kids he grows up with will die of heart attacks in their 30s and 40s, he'll survive into his 70s and have 6 fat little kids of his own. And six or seven generations down the line, he'll have hundreds of descendants who can eat at McDonalds without any greater risk of heart disease.

Okay, that maybe isn't really happening now, but something like that is.

The thing to keep in mind about human evolution is that evolution isn't something you can see in a lifetime, or even several generations. That lack of perspective makes it difficult for us to guage our own adaptations.

[MerinPally]

Animal uses head to headbutt things as defense/attack.

Skull hardens as result.

Generations and habits pass on.

The hardened skulls become harder, and eventually forms a layered nub

The layer nub generations later forms into a horn.

I doubt it's a conscious thing at all.

But, on the flipside, I'd REALLY like to know how Octopi evolve with Chromataphores. Not sure what the process is for that... same with Butterflies having eye spots on their wings. How did those develop? Was it purely a psychological knowledge and fear of eyes that perhaps subconsciously influenced a physical manifestation?

What you are describing is called Lamarckian Evolution, which is wrong. The final goal is the same but how it gets there is incorrect. Lamarck believed that should say a giraffe not be able to reach the highest up leaves but wanted to, it's neck would grow so that it could - and it would then pass this adaptation onto it's children. Darwinian Evolution which is accepted as how things happen, says that the giraffe with the neck that can't reach he top leaves will be less likely to pass on it's genes and will probably die as a result of lack of food. Those with longer necks will be able to reach and are going to be better fed and will be more likely to pass their genes on, so offspring will have longer necks. How one of them had a longer neck than the others to begin with? Because of mutations that happened over many many many generations.

[Bad Ashe]

i feel that future generations of americans are going to evolve tiny little t-rex arms and hunchbacks.

why? because all the kids do these days is hunch over with a smartphone in their hands. dont really need all that arm mass just to do that...

[nameuser]

How giraffes became a species: The animals that were born with a longer neck had a bigger chance to survive because they could eat the leafs that were higher up in the trees and get food. and so they had a better chance to pass on the genes.

Simple as that. Theres variations in every animal and living things and those who can better adapt to the environment can better survive. Its an inevitable process.

[CynicalOtaku]

How giraffes became a species: The animals that were born with a longer neck had a bigger chance to survive because they could eat the leafs that were higher up in the trees and get food. and so they had a better chance to pass on the genes.

Simple as that. Theres variations in every animal and living things and those who can better adapt to the environment can better survive. Its an inevitable process.

That's really only half the equation. The animals with longer necks eat more leaves and pass on their genetic code better. Because the trees need their leaves for photosynthesis, the taller trees with their leaves higher off the ground lose less leaves to the animals. What results is an "evolutionary arms race" where we wind up with very tall trees with long trunks and leaves high up off the ground, and animals (giraffes) that have kept pace with long necks to continue eating the leaves.

Also, natural selection isn't the only factor. Sexual selection is a powerful motivator too. Ultimately, everything is a trade off and compromise: Females tend to prefer flashy males, but flashy males can be risky in high-predation situations. A good example of this is an experiment done with guppies where identical groups of guppies were allowed to grow in three different environments:
1) a predator free environment
2) a low-pressure predator environment
3) a high pressure predator environment

In the first and second environments, the spots on the male guppies (rather quickly) started to contrast with the gravel bottom of the experimental environment, while in the third environment the spots changed to blend in.

Dawkin's "The greatest show on earth" is a great primer on how evolution works and also the overwhelming preponderance of evidence we have for evolution. Basically, all of modern biology works because of evolutionary theory.

One thing to keep in mind is most evolution works on geological time frames. Our first evidence of life dates back over a billion years ago. Multi-cellular life has been around for about half a billion years.

[Spectral]

Dawkin's "The greatest show on earth" is a great primer on how evolution works and also the overwhelming preponderance of evidence we have for evolution. Basically, all of modern biology works because of evolutionary theory.

Jerry Coyne's Why Evolution is True is another very good starting place for people.

[CynicalOtaku]

Jerry Coyne's Why Evolution is True is another very good starting place for people.

I've heard good things about it and it's on my reading list.

[mvaliz]

What you are describing is called Lamarckian Evolution, which is wrong. The final goal is the same but how it gets there is incorrect. Lamarck believed that should say a giraffe not be able to reach the highest up leaves but wanted to, it's neck would grow so that it could - and it would then pass this adaptation onto it's children. Darwinian Evolution which is accepted as how things happen, says that the giraffe with the neck that can't reach he top leaves will be less likely to pass on it's genes and will probably die as a result of lack of food. Those with longer necks will be able to reach and are going to be better fed and will be more likely to pass their genes on, so offspring will have longer necks. How one of them had a longer neck than the others to begin with? Because of mutations that happened over many many many generations.

Why is it wrong? Why can't it be gradual?

I do not believe that the Giraffe species suddenly "appeared" with already ridiculously long necks and began eating the leaves off the tops of trees.

It makes more sense that they first started off as smaller land-dwelling animals who reached up for smaller trees, and over the years developed larger and larger necks when reaching for higher trees... especially when considering the trees themselves also evolved - probably to grow higher and higher.

I've never heard of this "Lamarckian evolution"... what I'm talking about is Darwinian Evolution. The idea that a species ADAPTS to its environment which causes physical changes. Those changes do NOT happen overnight. That is what he discovered in his studies at the Galapagos islands that showcased the different adaptations of all the various animals, thus causing changes.

[Leonora]

the one thing i never really understood from evolution is how exactly does an animal evolve? i know they evolve to adapt to their environment and lifestyle but how exactly does an animal say to itself "this is shit things need to change" is it a sub conscience thing?

There is a theory about how it works. there have been experiments, and stuff is dug up that might agree with this theory. A lot of that theory is being expressed in this thread.

But to the question of 'how does it exactly work' we have to say; we dont know. For the evolution as postulated in the theory nobody has ever observed how it works, as this kind of observing only happens for at best a few hundred years and evolution is supposed to go much slower than that.

[CynicalOtaku]

Something else to keep in mind with evolution: Generally, only one species will generally hold a specific niche in a given area. Contenders for that niche will either out-compete or be out-competed. Humans are a good example: Not too long ago there were a number of primates with the same potential as us. For example homo neandertalensis and homo floriensis. Ultimately, tribes of homo sapiens killed or simply incorporated the others (in fact, all of us humans have some trace neanderthal DNA).

---------- Post added 2013-03-09 at 11:42 AM ----------

There is a theory about how it works. there have been experiments, and stuff is dug up that might agree with this theory. A lot of that theory is being expressed in this thread.

But to the question of 'how does it exactly work' we have to say; we dont know. For the evolution as postulated in the theory nobody has ever observed how it works, as this kind of observing only happens for at best a few hundred years and evolution is supposed to go much slower than that.

Ummmm...what?

No, evolution has been observed. Evolution has been observed multiple times and in multiple situations. Evolution is a "theory" in the sense that gravity is a "theory".

[Spectral]

But to the question of 'how does it exactly work' we have to say; we dont know. For the evolution as postulated in the theory nobody has ever observed how it works, as this kind of observing only happens for at best a few hundred years and evolution is supposed to go much slower than that.

Are you aware that you're spouting nonsensical creationist tropes? Evolution's observed both in labs and in the wild all the time. Selective pressure applied to organisms absolutely, factually, changes the genetic makeup of a population over time.

[mafao]

Why is it wrong? Why can't it be gradual?

I do not believe that the Giraffe species suddenly "appeared" with already ridiculously long necks and began eating the leaves off the tops of trees.

It makes more sense that they first started off as smaller land-dwelling animals who reached up for smaller trees, and over the years developed larger and larger necks when reaching for higher trees.

I've never heard of this "Lamarckian evolution"... what I'm talking about is Darwinian Evolution. The idea that a species ADAPTS to its environment which causes physical changes. Those changes do NOT happen overnight. That is what he discovered in his studies at the Galapagos islands that showcased the different adaptations of all the various animals, thus causing changes.

You are interpreted what MerinPally said incorrectly. In fact, he is talking about gradual evolution. He never suggested that changes happen overnight, he explicitly writes about changes over multiple generations.

Your mistake is that you are talking about 'adaptation', while in fact what happens is mutation+selection. In another words, random changes in the DNA+a selection mechanism can lead to adaptation, but evolution is not always about adapting. For instance read CynicalOtaku's post above.

[mvaliz]

You are interpreted what MerinPally said incorrectly. In fact, he is talking about gradual evolution. He never suggested that changes happen overnight, he explicitly writes about changes over multiple generations.

Your mistake is that you are talking about 'adaptation', while in fact what happens is mutation+selection. In another words, random changes in the DNA+a selection mechanism can lead to adaptation, but evolution is not always about adapting. For instance read CynicalOtaku's post above.

Ummmm... serious question, what's the difference? Mutation+selection is adaptation, isn't it? Obviously not a conscious behavioral adaptation, but it's still adaptation in the biological sense.

[Deadvolcanoes]

Here's an interesting video that explains evolution in a very simple, rudimentary way, through an interesting experiment. If you have five minutes, give it a watch:

http://www.snotr.com/video/7811/Demo...on_with_a_line

[Googolplex]

Its caused by random mutations, the animal doesn't decide anything.