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A Question About Evolution


Mintaka

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There are always natural variations in populations, in humans natural height varies at least by 24" across the human population, if height suddenly became a driving force for success as a human being (lets say suddenly only people who were good at basket ball could survive and reproduce) The natural human condition would move toward more tall people, if the selection pressure was height short people might disappear altogether. But to answer your question, no, humans are quite unlikely to grow wings so they can fly to get food even if it was a gradual process but if we did we would no longer be humans because our arms would become the wings... But for humans we are far more likely to build a ladder to reach the food than evolve wings, trust me on this, it's what we do....

 

As for giraffes their long necks didn't appear over night or due to a giraffe longing for the fresh tender leaves at the top of trees. But the giraffe ancestors that had slightly longer necks (much like the tall humans) would have a slight advantage, as their height increased this advantage would increase as they had access to food most other animals cannot get to. Over many many generations this has resulted in the long necks of the giraffe.

 

so the key phrase here is " over many many generations" ?

 

These changes happen slowly and gradually because each generation sees a slight increase in advantage for one specific quality over another , and the taller giraffes with this advantage start breeding together and increasing the likelihood of taller offspring?

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Was there a group of short-necked giraffes who died out because trees became taller and the leaves more innacessible, giving the giraffes with the hidden "tall-neck gene" an advantage?

 

All giraffes die. The ones with longer necks had a survival advantage because they could reach higher in the canopy where there was less competition for food (whether or not the trees got taller). The only competition current giraffes have for food is with elephants because they can knock trees over.

 

Giraffes with longer necks lived longer, more productive lives. Their children lived longer and more-productive lives. As a result, over time, longer-necked giraffes were better at successfully reproducing and populating an environment—replacing, in a sense, the shorter-necked giraffes.

 

By "longer" and "shorter" I mean incrementally so. It didn't happen all at once.

 

What if for some reason humans could no longer get their food supply on the ground, and had to fly 100 m up into the air to obtain it,

 

There are many examples where species like insects (flying insects) or mammals (bats) evolved wings because it gave them some survival advantage. The change doesn't happen overnight.

 

I assure you, by the process of evolution alone, in 100 million years humans will not look like they do today. They won't really even be "human". They may have wings. Who could say.

 

is there some hidden / recessive gene which would enable us to adapt to be able to grow wings to fly and reach our food?

 

To have wings is too complicated to be expressed with a single gene. Because of this, evolving wings is a slower precess than changing color.

 

The same evolutionary process can go the other way. Chickens that find themselves in an environment where flying offers no survival advantage can slowly lose their wings and their ability to fly. In environments where birds have few, if no, natural predators and abundant food, they have often lost their ability to fly. Kakapos are a good example (as are many flightless birds in the galapagos)

 

Their ancestors suddenly found themselves in an environment where flight was unnecessary, so their wings got shorter and less functional.

 

Would the necessity of our survival force us to grow wings in the same way giraffes got long necks?

 

Wings help things fall just as much as they help them fly, so the first survival advantage that would impact evolution would likely be the necessity of dropping long distances without injuring ourselves. If our survival depended on doing that then we might, for example, start to look like this,

 

 

which wouldn't allow us to fly, but would help us fall greater and greater distances and it would be a very small change to our DNA. From there, gliding longer distances or falling greater heights might offer a survival advantage. From there it wouldn't take too long to evolve functional wings.

 

Flying squirrels, for example, might look more like bats and be able to fly in... certainly less than a million years.

 

~modest

 

EDIT---> Sorry, I wrote this before noticing Moontanman's reply which stresses the same things.

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so the key phrase here is " over many many generations" ?

 

These changes happen slowly and gradually because each generation sees a slight increase in advantage for one specific quality over another , and the taller giraffes with this advantage start breeding together and increasing the likelihood of taller offspring?

 

 

Yes, I think you have the gist of it, the sexual component is often important too. In some people women tend to like taller men but it evens out because their is not enough advantage to being tall to make the genes for short people disappear but if the gene or trait that gives you an advantage in life also makes you more sexually desirable you'll get results much faster, it's how the tails of peacocks evolved even though the tail makes the males easier prey, the girls just love those big tails.

 

The taller giraffes were not only taller but the taller individuals were healthier due to better food making them more desirable to females, males also look for healthy females so the trait of long necks is double reinforced by environment and by sexual selection, sex is really at the heart of evolution of complex animals IMHO.

 

Even for humans it's not unheard of for women to seek out males with the physical properties they like to have a child with, even if love or a relationship is impossible, good teeth (smile), clear skin, muscular build, good personality or for some women the alpha male status of the individual is more important than him being a nice guy. These traits that women (and men for that matter) look for in their mates are signs of health and status both indicate a good chance his offspring will be equally successfully at attracting males or females. And so it goes, do genes drive us or do we drive the genes? that is the question, :lol:

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most people take evolution for granted now. But the more I watch nature programs about animals which have 'adapted' to be camouflaged against a certain environmental background,

 

or an anteater which has evolved a super long snout and a super long tongue and defensive scales, or a giraffe which has evolved a long neck to reach its faviourite leaves,

 

my question is HOW does this happen? Preseumably giraffes started out with very short necks and they evolved to be longer and longer?

 

But how does one generation pass this change on to the next?

 

Simply through wishing it to happen, by WANTING to reach higher leaves?

 

I cannot fly.

 

I would really love to be able to,

 

I would love to have wings,

 

and I guess I'm not alone in wishing this.

 

If I pass this wish or desire to fly onto my offspring, or enough of us do this,

 

is it possible we will evolve to be able to fly one day?

 

Will we start to srpout wings over the next few thousand years?

 

I have no doubt you are right that animals do evolve.

 

My question is WHY and WHAT DRIVES THESE PHYSICAL changes?

 

If we look to some of the giraffes cousins we may see an answer. Both the Okapi and the deer have rather long necks. In a sometimes arid place like the African savannah, those herbivores that can eat more of their food will will be more likely to survive. Over small periods of time, say a dry year or a decade long drought, the small differences in neck length won't have enough time drastically effect the general makeup of the gene pool. But that area of the world has, as have all areas, experienced prolonged periods marked by low precipitation and increased temperatures, resulting in less and more sparse vegetation. During these extended periods of time, minute differences in neck length, say an inch, could provide enough of an advantage to those with the longer necks that they come to predominate the gene pool. An extra handful of leaves up high may not be much, but in desperate times they may be the difference between life and death.

 

When an organism reproduces itself there is sometimes an error in the genetic replication (far more pronounced in sexual rather than asexual reproduction, as are most things). This error can lead to a massive birth defect. Or in can result in a trait that better hides the creature from predators. Or it can do nothing much at all. Much of our genetic code is virtually useless (As seems now, of course. Even though we can not yet tell you exactly what each gene does, we can be pretty sure that a large number of them don't do much of anything at all) and hangs around because there's no environmental pressure forcing the gene to disappear. But sometimes, something in the environment changes. This change may make a previously useless gene into one with survival value, or it may make a previously useful trait very dangerous for the individual. Random mutations occur almost constantly, as seen across the whole gene pool. Most are minute, useless, and quickly emerge and disappear. Some hang around for awhile, some are useful and some are not. A change in the environment may change whether or not any particular trait is beneficial or not.

 

The ancestors of giraffes probably looked much like an Okapi or a gazelle. Due to a random genetic change, and an environment that rewarded those with that change, and aided by typical variability within a gene pool, the ancestors of giraffes with longer necks survived more often, especially during the hard times. As time went on this trait came to be more prominent, resulting in the creature we see today. Along the way the giraffe has found other benefits to being so tall. Giraffes can act as sentries, able to see the onset of predators long before other animals can.

 

The explanation for why any specific organism has any specific trait will always be complex. But the underlying mechanics of evolution remain the same, regardless of the particular situation: During reproduction it is possible for random changes to be made to the genetic code being transferred or copied. The environment that an organism inhabits determines whether or not a trait in the animal is beneficial. If one creature has a trait that gives it an advantage over others than that animal will foster more offspring, spreading the useful genetic trait. Given enough time, those with the genetic makeup that best makes use of the environment will come to dominate the genetic pool. Thus evolution happens.

 

 

 

 

 

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so the key phrase here is " over many many generations" ? These changes happen slowly and gradually because each generation sees a slight increase in advantage for one specific quality over another , and the taller giraffes with this advantage start breeding together and increasing the likelihood of taller offspring?
E.O Wilson (The Diversity of Life, 1999) indicates that a single dominant gene for some trait, if it enjoys a 40% advantage in survival or reproduction as opposed to a recessive gene for the same trait, can change from a frequency of 5% WITHIN THE POPULATION to 80% within a time interval of ~20 generations. For humans, this amounts to ~400-500 years; for dogs ~40 years, for fruit flies ~1 year, for bacteria a few days.

 

So, the words "over many many generations" range in "time" from 100s years to a few days depending on the species. The concept "slowly" as relates to the tempo of natural selection is very much relative to the species under consideration.

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Evolution happens more or less randomly.

 

With each generation, there is a chance of a mutation.

 

If a specimen mutates, and the mutation helps it, then it is likely to survive and pass the trait on.

 

And so evolution happens.

 

 

I think thats the way it happends but SlOWLY and they could not decide so if somebody wants wing Im afraid it doesnt work that way

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