A few questions on natural selection

[Manraj singh]

I know very little about natural selection, so:
Why didn't all the creatures evolve? I mean , why is it that some fishes came to the land, or why did not all monkeys turn into humans? And is it possible that someday the monkeys on the trees turn into humans?

 

[Travis_King]

Read the wiki to get a basic understanding of evolution and natural selection: http://en.wikipedia.org/wiki/Natural_selection

Regarding your second point: No. It is possible that some small population of "monkeys" evolves into a separate/new species over the course of several hundred thousand years, but they will never evolve into humans. The most basic point about human/monkey evolution is: "We did not evolve from monkeys." We evolved from a common ancestor.
See here: http://cnx.org/content/m44696/latest/Figure_29_07_03.jpg

 

[Manraj singh]

Thank you

 

[Jobrag]

Suppose you have a group of apes living at the edge of a forest, one male has a genetic mutation that allows him to climb trees better, he takes some of the females deeper into the forest where his offspring inheriting the tree climbing gene thrive in the forest, another male mutates to walk upright more easily and the same thing happens on the plains. This is horribly simplified but different mutations and those mutations occurring in different environments will cause species to diverge.

 

[Manraj singh]

Oh. So 'adapt to survive.'

 

[dkotschessaa]

Oh. So 'adapt to survive.'

Yes, so the answer to "why didn't all creatures evolve" is really, "they did all evolve." Every creature alive evolved to fit it's particular niche.

 

[Manraj singh]

Yes, so the answer to "why didn't all creatures evolve" is really, "they did all evolve." Every creature alive evolved to fit it's particular niche.

Thats my question. If i am not mistaken, fishes came into existence before land animals. So, why did only some fishes come out, or 'want' to come out.

 

[micromass]

Thats my question. If i am not mistaken, fishes came into existence before land animals. So, why did only some fishes come out, or 'want' to come out.

First of all, there is no "want" in evolution. Evolution is a mindless process. It just happens. It has no goal or desires.

What if I ask you the following question: "Some Europeans came to America when it was discovered, why didn't they all come?" It's not an answer, but you should think about it. A possible answer is that many Europeans didn't have the financial means to go to America, and a lot also had it quite good in Europe.

In the same way, a lot of fish didn't have the right genes to come to land. And they had it quite good in the water, so they didn't suddenly all die if they remained in the water. So there is no real disadvantage in staying in the ocean. So their offspring will also not have the right genes and will also not go on the land.

Compare this with the evolution of the peppered moth: http://en.wikipedia.org/wiki/Peppered_moth_evolution Here we indeed have a significant disadvantage for the moths who were not black. So the genes of black moths were much more likely to survive than the genes of the white moths. This did in fact cause most of the white moths to be replaced by black moths.

 

[Manraj singh]

Thanks

 

[Phobos]

It's important to understand that evolution is not a ladder of progress that leads to humans. It's a great branching of different variations that adapt to different environments. Modern fish are just as "evolved" as modern humans. In the evolutionary past, some types of fish had the right physical make-up and found benefits to spending some time on land. Other types of fish did better by staying in the water.

 

[DiracPool]

Why didn't all the creatures evolve? I mean , why is it that some fishes came to the land, or why did not all monkeys turn into humans?

The rule of thumb in natural selection is "if it works, don't fix it." Fish are perfectly fine living in the water and I'm sure most prefer it to stay that way. The fish that came to land were the ones that got stranded on the shore when the tide went out, or the pond dried up. While most of them died, a few had some genetic "defect" that allowed them to survive on land, and that's where that came from.

Look at the Coelacanth, it hasn't changed much at all in 400 million years. Why? Because it didn't need to, it got by just fine with what it had and it stayed that way.

If you want to go even farther back, every living thing you see around you all evolved from a primordial prokaryotic cell. A cell very similar to the the bacteria in your gut. So here's an example of a living creature that hasn't changed much at all in several billion years.

http://en.wikipedia.org/wiki/Prokaryote

The oldest known fossilized prokaryotes were laid down approximately 3.5 billion years ago, only about 1 billion years after the formation of the Earth's crust.

When we trace the history of brain neurotransmitters and neurohormones, we find that chemicals such as acetylcholine, dopamine, norepinephrine, serotonin, etc. are found and conserved in these very primitive organisms, which heavily supports the model that everything evolved from a single (or a few) primordial prokaryotes.

And is it possible that someday the monkeys on the trees turn into humans?

I certainly hope not, we already have to many humans, we don't need any more in my opinion. Plus, history has taught us that we would probably kill off an intelligently forming primate species before it evolved human-like intelligence. There was a time when there were several hominin species alive simultaneously. Eventually, though, about 30,000 years ago, our Homo Sapien Sapien ancestors killed them all off. And if you think we've "evolved" out of that psedo-privileged brutality, you're mistaken. Just ask Jane Goodall or Dian Fossey (rest her soul). We are in real danger of poaching our few remaining great apes out of existence.