Why aren't our evolutionary ancestors extinct?

Environmental pressure.

How about black bears? if they lose their habitat then what will they evolve into? or what about polar bears?

 

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werewolves

 

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John, an organism itself doesn't ever evolve. A species evolves, or a group within a species evolves. Often over many many generations.

Your thinking error is that you only see the begin- and endpoint, which both don't actually exist unless defined by man.
Evolution usually happens very gradually. It's only after many many generations that an isolated group (for instance) becomes a different species from the group they split off from.

 

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No one can tell, although dying out seems a more than likely outcome.

 

I think it is a serious question because all we have witnessed is extinction. So now tell me where does that leave this evolution theory?

 

Most species do die, most have died. Since there are still many species left, it doesn't seem like a deal breaker. There very fact that there are still millions, if not billions of species, means that speciation occurs.

 

I have suggested a course of action to help you understand what is going on. Until you have read up on the subject, your questions will make no sense and you will not understand my answers.

Using algebra as an example, consider the equation

x =
-b +/- the square root of (b^2 -4ac )
------ --------------------------------
2a

Clumsy layout but the best I can do.

You are asking me to explain "a" which I cannot do without going through all the steps necessary to establish the above general solution of a quadratic equation. Life is too short so, I am suggesting that you read an introduction to algebra and learn to handle a few equations. which will enable you to understand my answer. Otherwise, if I just reply that "a" is the co-efficient of x, you will ask me what a co-efficient is and why x needs one. Get the idea ?

 

But then you are assuming that the organism would have the ability to predict changes or even know that things would stay exactly the same but for what reason? And did you ever consider that these changes would have had to happen millions of times?

Explain the evolutionary need\reason for a jelly fish.

 

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Please read this post: http://www.sciforums.com/showpost.php?p=1867825&postcount=65

 

So species replenish themselves? Extinction means forever. The fact is that cataclysmic events (to a particular species) do not happen often.

 

Enmos,

I am not an idiot, not by a long shot. Here is the gist of that post:

I already acknowledged that changes (relatively slight) can and do occur but from your own example they are still RABBITS.

 

Yes, they are still rabbits

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That was not by far the gist of that post though.
How about this:
"Key is that beneficial genes for the new environment must already exist within the genepool before it is selected upon by environmental pressures."

Please tell me you are trying to understand..

 

John,

I cannot understand why you avoid educating yourself like the plague. Spend some time reading as has been suggested. Then ask questions if you have difficulties !

 

No-one is saying that except you johnboy

considering we have somewhere on the region of 3.5 billion years of evolution under our conspecific belts, where is the problem there?

To make more jellyfish

 

The way you use "need" seems to me to be the issue. Humans did not need to evolve in some absolute sense, nor did intelligence, nor did birds' wings.

Let's say all the food is high up in trees and I aims to gets it. Presumably, if that is my only food and my species is surviving, I must be getting it somehow (perhaps we live on the food that happens by chance to fall to the ground). However we are eating, we are eating and there is no "need." But suppose the food that falls is insufficient to sustain our whole population. Now what happens? Some of them starve, and the ones that starve are disproportionately likely to be the ones who had some comparative disadvantage in getting that food. (Why? it could be any reason. Maybe they have poor eyesight and can't see the food as it falls or in the distance while others can. Perhaps they are slow and can't get to the falling food before it's scavenged. Perhaps they are weak and others beat them up and take the food. It could be any trait that puts them in the group that starves.) Those traits that disproportionately led to the starvation of certain members of the first few generations start to become less and less prevalent in the population as a whole. The population's characteristics change.

Conversely, the ones that tend to remain are the ones that have a comparative advantage. Suppose many generations in, one animal as a result of a random mutation develops the ability to climb, or slightly better senses to see/hear/small the food, or better footspeed, or greater strength, or any other trait that gives him a slight or great advantage over his peers. Assuming the group as a whole is still breeding in numbers that lead to starvation, his trait is disproportionately likely to allow him to survive. He is disproportionately likely to have offspring and to pass that trait on. In succeeding generations, that those with the trait are more likely to succeed than those without and so the trait becomes more prevalent in the population as a whole. Again the population's characteristics change.

"Speciation" is the cumulative effect of all of these changes over the course of many generations. Any one individual change is likely not enough to result in a new species, but a dozen, a hundred, a thousand? At some point the new population is so different that a clear demarcation across time can be made.

As for humans and intelligence, we developed it because it was helpful in our survival on balance. It comes at a high cost given the many calories it takes to sustain the brain and the high levels of protein required. What must have happened, under the natural selection model, is that (i) ancient pre-humans faced challenges, (ii) some pre-human had a random mutation that led to greater intelligence, (iii) he and his descendants with the trait were disproportionately likely to overcome the hurdles to reproduction that they faces, and so the trait thrived. If those pre-humans had (randomly) developed wings, or a better immune system, or the ability to hold one's breath for three straight hours *and* those traits helped them survive better than the the rest of their competitors, then we'd have those traits instead, but that is not how it happened.

Let's say (again) that the food is very high in the trees and someone develops wings. Let's also say that another individual, without wings, develops the ability to throw rocks with pin point accuracy. Suppose that the rocks can be used to knock the food out of the trees (and, for arguments sake, let's suppose they can't be used to kill our flying competitors). What happens in that case?

Nature has several paths it might take (likely even more than I am imagining). First, it might be that wings are expensive...it takes a lot of energy to fly your whole body up into the trees, and comparatively little to throw a rock. It might be that rock throwing is superior in efficiency to wings and that the rock throwers will out-compete the bird-men. Second, it might be that the wings are more efficient (perhaps the fliers gather more food per trip than the rock throwers, or catch the rock throwers food as it falls). Third, two separate populations might develop, one living in one area and the other in a second area, eventually becoming two separate species with different strategies for food gathering.

In either case, they neither needed to develop the ability to fly nor the ability to throw rocks, those traits appeared randomly and happened to be beneficial in light of the environmental contstraint that the species faced.

 

Trying to explain evolution to a religious fanatic is like teaching a pig to sing - it gets you knowhere and it pisses the pig off

 

synthesizer-patel,

And you just contributed absolutely nothing.

 

The problem is that I am not a religious fanatic or even religious at all.

 

Species have an average lifespan of about a million years. So, that's like- a particular kind of bird might die out, but similar birds will still go on.

 

John if you are not willing to learn then why are you here ?