Djalapeno86

Oh, I got it now. Thanks for your help~!

So in general what I'm getting is that evolution is caused by gene crossover & mutation, natural selection, and change of behavior. But I still don't get how natural selection & change of behavior result in physical changes (or any other factors that I might've missed). Note that I'm focusing on physical evolution, not behavioral or any other type of evolution. E.g. I'm interested in how horses get bigger overtime and elephants get smaller over time. If external pressure cannot change gene (or the gene of the offsprings), then what can? Can you give me a specific example of what causes physical changes of a species, then? Maybe that'll be clearer for me. Nature doesn't select for what is good for 'you' but what allows offspring. Take peacocks, their tails are not really what one would consider 'good for you'. It doesn't give an advantage for survival, but it does attract peahens so they can reproduce. Nature doesn't care if they get eaten by a predator so long as they survived long enough to reproduce. BTW peacock's tail is actually 'good for them' since it supports one of the two basic instincts of living being, right? Survival of self and survival of the population (reproduction). Again, this is natural selection, I'm guessing. I'm still wondering what causes physical changes of the population and more importantly how.

For #2: Aren't wearing braces and, let's say an environmental condition that forces a duck to hunt underwater (just making this example up), are both physical alteration? I know that wearing braces won't change your genetic information, but how does the later example do in such a way that it evolved to....emmmmm....platypus? Sorry I couldn't find a better example, but you got the premise. Focusing #2 (I think I got the ideas for my questions #1 and #3): Let's take a population of giraffe for example. Let's say in the beginning there are 50% short necked ones and 50% long necked giraffes. Pulling your own neck over 30 years won't change any of your DNA information, correct? What constitutes evolution are: 1. Mutation 2. Gene crossovers The question is how do we end up with all long-necked giraffes today? Is it because of: 1. Many of the short ones died without having the chance to breed? 2. Or is it because nature has determined that the dominating trait (if a long-necked giraffe and a short-necked giraffe mate) is "long-neck"? Or is it a combination of both? 3. Pulling their neck actually does change their genetic information...very very slightly. And if your offsprings keep doing the same thing, and their offsrpings etc, then it'll build up and you'll have a slightly taller giraffes and so on. If the first one is true, then in our society evolution is not required because: 1. People support each other to a certain extend. People won't die easily as inferior giraffes. 2. Technology improves survival And therefore the human population won't converge to a single definable population with "ideal" traits. The diversity will be maintained at least to a certain extend. If the second is true, then it is a scary thought that nature actually "selects" what traits are good or bad for you. But I know this is unlikely based on direct observation of human population. The third sounds appealing to me. But I don't know how valid that is lol.... Thanks for all the responses guys! I am pretty satisfied with issue 1 and 3, but I'd like to explore more on issue 2. Let me just copy my reply to Ringer: ========== Focusing #2 (I think I got the ideas for my questions #1 and #3): Let's take a population of giraffe for example. Let's say in the beginning there are 50% short necked ones and 50% long necked giraffes. Pulling your own neck over 30 years won't change any of your DNA information, correct? What constitutes evolution are: 1. Mutation 2. Gene crossovers The question is how do we end up with all long-necked giraffes today? Is it because of: 1. Many of the short ones died without having the chance to breed? 2. Or is it because nature has determined that the dominating trait (if a long-necked giraffe and a short-necked giraffe mate) is "long-neck"? Or is it a combination of both? 3. Pulling their neck actually does change their genetic information...very very slightly. And if your offsprings keep doing the same thing, and their offsrpings etc, then it'll build up and you'll have a slightly taller giraffes and so on. If the first one is true, then in our society evolution is not required because: 1. People support each other to a certain extend. People won't die easily as inferior giraffes. 2. Technology improves survival And therefore the human population won't converge to a single definable population with "ideal" traits. The diversity will be maintained at least to a certain extend. If the second is true, then it is a scary thought that nature actually "selects" what traits are good or bad for you. But I know this is unlikely based on direct observation of human population. The third sounds appealing to me. But I don't know how valid that is lol.... ======== Any idea?

Hi everyone, I'm an engineer who enjoys philosophy and science but nevertheless forgot a lot of things about evolution. Recently I had a long discussion with my friends and came up with questions of which I can't answers on the internet and textbooks. 1. Are we still evolving (obviously it should be so)? But what is the evidence that we have been evolving in the last...say 500 years and what are these changes? Any legit reference? 2. Can external conditions cause genes to change? If yes, why parents with unaligned teeth who wear braces will still have kids with unaligned teeth? If no, then how do species evolve in the first place? 3. People have different skin color, height, hair etc and therefore have slightly DNAs, right? We call this variation, I believe. Chimpanzees' DNA is 97% similar to ours (or some number along the line). What is the cutoff that distinguish variation and different species, then? 99.99%? Thanks in advance!