Evolution is not a driving force, it's observation. It does not force or direct anything.

It seems that every time I talk about evolution, someone has to point that out Of course I understand perfectly that evolution is not a 'driving force', it has no goal, it's just what we see as a result of genes combining, expressing, "surviving" or "extincting" depending on a number of impersonal, neutral factors. It's just that some times the phrasing even in books like the one I'm reading makes it a bit "foggy" to really grasp what's *really* going on. For instance, Dawkins talks about animals that "got out of the sea" into the land, and then went back into the sea(dolphins,whales). The instictive response when I read that is that some small population, for unknown reason, decided to literally get out of the water, and stay in land, where it got its legs, while I'm sure it's not quite what happened. I guess some creatures were out of necessity driven out of the water environment, maybe because of geological changes, and there those that their organs resembled legs more, got better chance at passing of the genes and resulting in a population with what we call "legs".

It's harder to imagine how we got from gills to lungs though; the book says that at one time all creatures lived in the sea. So, some animals with gills got out, for any reason, into land areas, and survived enough in order to substitute the gills with lungs? Which came first, the 'get out of sea' thing or the 'lung' thing? Did some species, while living solely in water, evolved into amphibians first, and then 'land animals'? How come? I imagine that, if we today we get all the fish(not dolphins or whales) of the earth somehow out of the water, all the billions of them would die in a matter of minutes or at least hours, without one exception, without some of them surviving in land long enough to produce other generations which would somehow 'adapt'. These are the stuff I have a harder time grasping.

I imagine that, if we today we get all the fish(not dolphins or whales) of the earth somehow out of the water, all the billions of them would die in a matter of minutes or at least hours, without one exception, without some of them surviving in land long enough to produce other generations which would somehow 'adapt'. These are the stuff I have a harder time grasping.[/quote]
Evolution doesn't work that way. It can, in extreme cases, but not generally.

The survivors in this case would be flukes, not "better adapted".

Closest in human world would be HIV immunity. There are several individuals which appear to be immune to HIV. Or more accurately, development of AIDS from HIV infection. These would be the "flukes". Unexplained random survivors, possible due to unrelated reasons.

But meanwhile it was shown that descendants of European plague survivors have statistically lower chance of HIV infection. Current research indicates that plague shares some common traits with HIV. While plague didn't discriminate and was fought with very practical methods, such as burning corpses or isolating villages, no infection is 100% effective. On each exposure, some are more or less susceptible. More susceptible ones will die more frequently, causing more of population to survive as resilient.

When it comes to single individual, these probabilities are small. But when looking at entire population, statistically significant deviations do occur.


Same for animals. Nobody threw a fish on the ground and it suddenly spawned legs. Some fish lived in shallow waters, some had larger and some weaker fins. When a rogue wave hit, those with stronger fins flipped higher and further and more of them fell back into water. Over course of time, these fish, as population, had stronger fins in general. With ability to flip back into water, the next criteria was ability to survive outside water. So those that could "hold breath" for longer again gained slight edge. Other traits had effects on other aspects of life.

I don't know the exact details, there are probably many now extinct organs involved, but "walked out of water" is not literal. It happens over millions of years, with many generations differing only slightly. The random factors also aren't drastic, they are more closely correlated to fluctuations in ecosystem, such as overpopulation of one species leading to decreased food supply and changes in species preyed upon.

But there is no One Fish which was the first to walk and it wasn't Two Champions which went on the beach and Did It to produce landwalking children.

You can find lots of information about this online.

This will start you off:
http://animals.about.com/od/amphibians/ss/landtowater.htm
http://www.sciencedaily.com/releases/2008/10/081015144123.htm
http://serendip.brynmawr.edu/exchange/node/1904

In general, consider how strong the selective pressure to develop means to live on the shores would have been. The first animals living on shorelines would be protected from their natural aquatic predators, and would have zero terrestrial predators. There also were unexploited food sources on land. This sort of selective pressure had no choice but to yield terrestrial animals.

As to which came first, lungs or being terrestrial, most scientists think lungs did. They think that lungs developed while fish were aquatic. I'm not sure of the details.

Well, AFAIK lungs are invaginations of the oesophagus, and it has nothing to do with gills. Most (maybe not most) fish have both gills and modified lungs today: swim-bladders.

The interesting thing about evolution is that we can still watch almost every "stage" of it. Like fish with lungs, fish with leg-like paddles. And they all live in a similar circumstance as our ancestors.

AFAIK legs "came" from fish, that lived in a mangrove-like environment, where they needed powerful limbs to be able to hide between the roots/branches from predators. They even left the water for small periods to escape from the predators, which became handy when waters got shallower.

If flying fish had lungs, maybe one day they will become truly flying creatures.


An important principle, which made me understand evolution a lot better, is that these mutations develop on the embryo, when it's only a few cells. So a big change/mutation is really just the mutation of a single cell for example. A grown up animal won't just spawn legs.

There is still one area which gives me confusion: "sexual selection".
I understand, that there are animals with a mutation that seems to be disadvantageous for survival but the animal can bear it and still survive.
But why showing it is more attractive to females? Or is it just by chance? It's a luck that the female is more attracted to a freak (and of course they reproduce)?

So the attraction is just a mutation too? So, by chance, the "attraction-to-freaks" mutation meats the "freak" mutation, and they reproduce, and they descendants inherited these mutations?

An important principle, which made me understand evolution a lot better, is that these mutations develop on the embryo, when it's only a few cells. So a big change/mutation is really just the mutation of a single cell for example. A grown up animal won't just spawn legs.

LOL! Do people really think this? I am not being condescending, I think it's a funny image to picture -- legs just popping out of a fish that then shrugs and takes off running.

If it's common to think of this kind of thing when people hear "mutation", then it sounds like one problem is that our educational system isn't doing a good-enough job of teaching the fundamental processes.

[quote name='szecs' timestamp='1313174119' post='4848355']
An important principle, which made me understand evolution a lot better, is that these mutations develop on the embryo, when it's only a few cells. So a big change/mutation is really just the mutation of a single cell for example. A grown up animal won't just spawn legs.

LOL! Do people really think this? I am not being condescending, I think it's a funny image to picture -- legs just popping out of a fish that then shrugs and takes off running.

If it's common to think of this kind of thing when people hear "mutation", then it sounds like one problem is that our educational system isn't doing a good-enough job of teaching the fundamental processes.
[/quote]

Well, not literally, but they don't think anything... They just don't understand how can big mutations happen.
At least I guess. Maybe I was the only idiot who thought that...

My guess is that rather than going strait from ocean to land fish went from the ocean into freshwater rivers starting with large ones and the transition to amphibians was the result of adapting to survive in increasingly smaller streams and ponds that would become shallow and stagnate during the dry seasons.

An important principle, which made me understand evolution a lot better, is that these mutations develop on the embryo, when it's only a few cells. So a big change/mutation is really just the mutation of a single cell for example.

When organism reproduces, it will not result in perfect replica or offspring. The DNA combination or replication process will introduce errors. There are mechanisms which correct such flaws but they do are not perfect either. If the defect results in dysfunctional organism, it will die of.

Twins are an example. While almost identical, they are not perfect copies.

When viewing population as a whole, there is a bell curve of such deviations. Mutation isn't needed and the term doesn't apply to such process.

Mutation is typically caused by external factor. In terms of evolution it is the unknown factor. It helps move out of local minima by introducing arbitrary changes. While most mutations will cause death of organism, some will survive. Mutation is rarely attributed to meaningful evolutionary step.

In theory, mutation could cause legs to appear on a fish. Instead, over course of many generations, average shape of fin slowly changes from one generation to another, eventually leading to something that is marginally better suited for land movement than it is for swimming.


Another analogy of this normal deviation is Telephone. Every participant makes best at replicating original message, but the final message is something completely different. In terms of evolution, a message that is somehow deemed unfit would stop such chain. A simple method would be enforcing a rule that words may only represent fruit. When one member in the link wouldn't not be able to understand the word as something describing a fruit, the chain would be broken. But despite such restriction, final word could trivially mean some other fruit than the original one.

They just don't understand how can big mutations happen.[/quote]
There is no "big" mutation.

An organism is either fit or not. We may perceive some physical deformity as "big mutation", but reproductive material affected tends to be minimal. And the serious defects typically caused by detectable single gene defects have commonly very adverse effects on reproductive ability.

Antheus, your differentiation between "mutation" and errors in DNA replication or meiosis is strange.

The term "mutation" as used by evolutionary biologists and geneticists includes errors in DNA replication and meiosis. These are by far the most common sources of mutation, actually.

And most mutations don't lead to the death of an organism. Most mutations lead to absolutely no or almost no effect.

The truth about evolution for you, sheeple: