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Comment by Tichy | Hacker News Reader

You've got it wrong. There is always variation in a population. If a new environmental pressure arrives, some of these variations end up being more successful than others. In some time you might not find any terns who can't dive deeply anymore. There is also a lesson in that that variation is important (for example also in economics, agriculture and so on) - don't bet your countries economic future on just one industry, for example. Evolution theory applies everywhere.

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I did not say there is no variation in population. Animals that survive have the ability to survive before environmental pressures. Why ? Yes there are variations among animals, and those that have the trait for survival, survive. The argument is how do these variations that survive get these important trait ? Especially when these traits are specialized to the environment. How do they evolve these specialized traits in time ?

You are only asking for the basics of evolution, every textbook should have you covered (or even Google). And it doesn't happen the way you imagine it, those traits don't have to evolve from one day to the next. Bears can live in Canada because they can hibernate, they didn't live there and had to learn how to hibernate on short notice when winter came.

Have you not read textbook that explained specialized traits as reaction to the environment ? How could that be possible when these traits are needed immediately. You miss the point, why don't we have thousands of animals with the ability to hibernate that don't need them ? Of course traits don't have to evolve rapidly if you already have them or don't need them. But why would you already have the ability to hibernate efficiently if you don't need it ? Why would a bird of prey evolve the ability to hunt from the skies at relative high speed before it can fly ? I'm sorry I read the books there are no legitimate answers. Like said I love science and technology.

> You miss the point, why don't we have thousands of animals with the ability to hibernate that don't need them

Because a tendency to hibernate is likely negative for survivorship when it's not necessary - if lots of other animals are moving around and you aren't, then something is more likely to come and kill you.

On the other hand, lots of animals have other varying traits that aren't obviously useful, but don't exact a significant enough toll to cause them to disappear.

> But why would you already have the ability to hibernate efficiently if you don't need it

Doesn't that assume that bears were transported into Canada and survived because they could hibernate? Isn't it perfectly possible that they moved further north gradually, increasing their tendency to sleep in cold conditions as they did so?

In case of hibernation it seems very plausible that an animal evolved to sleep longer and longer, to preserve energy. I don't understand your problem? It could also work this way: an environment had enough food to sustain 20 bears in winter. If they sleep longer, the environment can sustain 40 bears. If they sleep even more, 100 bears can survive. The population would then grow from year to year, while sleeping more and more. What books on evolution have you read?

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