Okay, I understand the concept behind adaptation, i.e. the changes made by living organisms in response to their environment. But on a more literal level, I have trouble grasping how it manifests. For example, suppose millions of years from now, our environment makes it necessary for us to grow tails and become tree-dwelling. Where does this evolution process begin exactly? How does it “suddenly” occur that a person or people begin to sprout tails by necessity? I’m not a creationist by any stretch but it just strikes me as odd that there is no divine intervention at work here. Does this make any sense?
It starts as soon as the first stubby armed guy kills himself while trying to climb the tree he has been forced up and it keeps on going for a very long time
Two key elements:
Survival
It’s not about changing; it’s about not dying.
If tomorrow, our environment made it such that everyone with a small nose died, only people with long noses would survive and have long-nosed kids. The people with short noses didn’t adapt (i.e. their nose didn’t grow to match the environment). The species adapted in the sense that the long-nosers became the next generation.
Random Change
You can see in the description above that there’s typically a lot of variance in a population, for example in nose sizes. But what about new features? Selective breeding can cause long noses, but not add a third eye. Clearly selective breeding won’t by itself turn an amoeba into a human.
Radiation (and possibly other things) can cause random changes in DNA. The vast majority of these changes are very bad, causing handicap or death. Every so often, a change comes along that’s beneficial. This trait gets passed to the children. Give the process millions of years, and amazing things can happen.
I like billehunt’s answer.
It may be that “adaptation” is the root of the problem. We are a very adaptable species. We use stairs, wheels, underground, above ground and tree houses, wear clothes, go naked, wear bark from trees (yikes) and weave cloth for clothing.
It is “variety” that gets us dark skin in the tropics, long noses in cold weather areas, upright walking, resistance to malaria, more or less hair than the next guy…variety and hundreds of thousands or even millions of years.
Variety is random, you don’t get what you want when you want it.
Are you driving with your eyes open or are you using The Force? - A. Foley
Thank you Billiehunt and Jois for your thorough explanations! Now in deed it does make sense to me. And to think I was considering that God played a role in this!
Yes. Ha ha, that would have been silly!
A further clarification: us “needing” tails wouldn’t automatically mean that we would grow tails. If some people had mutations in the tail direction, they would probably be selected for, and so on until full tails develop. But there is nothing inevitable about this. That’s a very important fact to remember: there is nothing inevitable about evolution. It’s easy to look at the development on humans, with such adaptations as opposable thumbs, and think that Nature someone how “knew” that opposable thumbs would be advantageous, and therefore provided our ancestors with oppposable thumb. It is a good metaphor, but don’t be confused into thinking that’s what happened. When we look back on evolution, we’re looking with hindsight, and it’s easy to say that there were ceratain adaptations that we “needed” to become humans as we know them today. But that doesn’t mean that there was a driving force behind evolution providing us with everything that we “need”.
Hmm… Smells funny this one…
For the record, evolutionary science says nothing about God being or not being there. One can certainly believe that God had and has something to do with adaptations past and present.
Now, if my hunch is right: There are (too) many creation vs. evolution threads over in Great Debates. If you wish to continue on the tangent that I believe you plan on given that statement, I suggest you head over there.
Yer pal,
Satan
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And now to quote C.H. Waddington, who was an eminent member of the neo-Darwinian establishment in the early 1950’s, “To suppose that the evolution of the wonderfully adapted biological mechanisms has depended only on a selection out of a hapazard set of variations, each produced by blind chance, is like suggesting that if we went on throwing bricks together into heaps, we should eventually be able to choose ourselves the most desireable house.”
I don’t believe that most evolutionary biologists agree that time alone, even millions of years, is sufficeint for chance mutations to produce such mechanisims as a functional eye or an egg.
Natural selection or even “radiation” are insufficient drivers for this process. In fact, the process is still not very well understood. Unfortunately, the scientific community is so busy defending itself against the creationists that very little serious discussion of the issue has taken place.
The Ryan,you have put your finger on the thing that irks me about explanations of evolution such as those found in “Jurassic Park”'s dreadful sequel “Lost World.” I mean the book, not the movie.
The book says that dinosaurs developed family structures because they needed to, for survival. Unless the theory of evolution has changed drastically since I was in college a million years ago, that absolutely cannot have happened unless you depart from the t. of e. and strike out in a new direction.
As others have stated, changes occur that make individuals more or less able to reproduce their kind, and those changes are therefore more or less prevalent in future generations. Nothing happens because it “needs” to. This kind of stupid reasoning makes me think the person pushing it is desperate to deny the possibility that there was any sort of designer involved in the way things are. It also reminds me of Lamarck, the Russian scientist favored by Stalin, who argued this way and was caught faking his data.
I actually think there was a designer involved, which prevents me from having to go through these logical contortions. I also think the designer made extensive use of evolution as Darwin envisioned it.
TheRyan wrote
Technically, that’s absolutely accurate.
But nature does know in the sense that some things are logical steps from previous steps. So nature waits around for the right random event before proceeding. When we find extraterrestrial life, the odds will be good that we’ll see a lot of similar steps in their evolution, like single cell to multi-cell, invention of sight, asexual to sexual, etc.
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Nothing like a quote fifty years out of date to shed light on the issue!
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I think you’re wrong about where the opinion lies. The evolution of the eye (to choose one example) is well explained in terms of natural selection.
As for the earlier claim that the vast majority of mutations are detrimental to the organism, that simply isn’t true. The majority of mutations are neutral, having no effect at all.
It was also mentioned that “sprouting a third eye” can’t happen from mutation alone. This is simply not correct- where do you think all those Amish people with six fingers come from? Simple (even single) mutations in genes can cause duplication of entire organs.
-Ben
SouthernXYL:
Technical details:
Lamarck is the biologist of the late eighteenth and early nineteenth century who, long before Darwin had entered the field) proposed that evolution was a continual record of achievement and that progeny inherited the characteristics that their parents had developed over their lifetime. (Typical example given: short-necked giraffes browse higher and higher on trees, they extend their necks to reach branches above the ones being browsed by goats and other critters, their offspring have minutely longer necks which they, in turn, stretch and pass on to their offspring.)
The Soviet biologist was Lysenko who did not so much fake his data (although that did occur) as demand that any theory and any evidence fall within the parameters that he had laid out. He rose to bureau chief under Stalin and forcibly his ideas on all practicing biologists and agronomists.
There is a small link between Lamarck and Lysenko in that one or two of Lysenko’s beliefs were taken from Lamarck’s ideas.
The tragic irony of that is that Marx was a great admirerer of Darwin (although he was grabbing a few of Darwin’s ideas and using them for political discussions that Darwin never intended).
Tom~
Thanks, Tom - I’d been looking for that stuff I thought I’d remembered about Lamarck, and I was remembering the wrong guy!
Darwin didn’t think so. Nor did Thomas Huxley. Of course, Ben has already determined that ideas more than 50 years old can’t possibly have any relevance today, so I’ll try this one (from only 25 years ago).
“When it comes to the vertebrate eye - that classic stumbling block of Darwinian theory - with its retina, rods and cones, lens, iris, pupil, and what have you, the odds against the harmonious evolution of its components by independent random mutations, i.e. by ‘blind chance’, becomes, pace Huxley, absurd.” - Arthur Koestler
I’d like to mention something here that should be taken into consideration when discussing genetic mutations, and may help clarify the picture a tad, at least as per mammals.
While I’m not positive this is universal, female mammals are generally born with all of their eggs already present in the ovaries - they are formed during fetal development, and all that remains is for them to mature to a fertilizable stage (is that a word?) in response to hormone stimulation. This means there is a very short time during which DNA alteration can occur on the female side of the equation - any changes must happen during fetal development at the time the eggs are developing.
However, male mammals produce new sperm constantly, in the millions. There is a much greater chance of a male’s sperm being affected in some way, and this change being passed on to whatever offspring is the result of that individual sperm. “Radiation” is not the only source of mutation - ingested or inhaled chemicals of various kinds that exist in nature can affect normal sperm production, and there are also simple ‘copying errors’ - when millions of sperm are being replicated every week, occasionally something is going to get screwed up and come out a tad different. Ever think about the possibility that you menfolk are the primary source of genetic variance?
Even a harmful mutation might not be weeded out by natural selection if it is a recessive gene. Even in a closed breeding situation (such as a kennel or cattery), recessives are almost impossible to eliminate 100% - in an informal breeding situation (in the wild, for example), a recessive might be passed on pretty much forever without ever really affecting the species.
Another way in which a harmful mutation can continue to exist is a gene that has varied expression. A good example of this is the Manx cat - I think most people are familiar with them - the ones with short or no tails. The Manx gene is a dominant with varied expression - in its most extreme expressions, there are spinal deformities, etc. that ultimately prove fatal to the cat. However, in its less extreme expressions, cats may have tails of varying lengths that have little or no effect on their survivability. So, although the Manx gene is basically a lethal gene, its variability of expression has allowed the Manx cat to continue and flourish.
Since my specialty is cats, I’ll use them to proved some examples of mutations that ‘don’t matter one way or the other’. The ‘wild type’ cat is called a brown tabby. Two separate mutations have occurred at the ‘brown’ locus that affect pigment distribution in the hair, and cause either a ‘chocolate’ tabby or a ‘cinnamon’ tabby. There is very little difference in the actual coloration of the cats to the uneducated eye - they all appear ‘brown’. It’s doubtful that such a minor color variation would have much affect on the survivability of the cat, either positively or negatively. As a matter of fact, captive breeding programs in the U.S. have produced ‘cinnamon’ tigers (brown stripes on a gold background) because the small gene pool brought together individuals that carried this recessive gene.
And, since my fingers aren’t tired yet, I’ll try an example of a mutation that might be harmful in some situations and beneficial in others. At some point in time, a mutation created a recessive gene that produces the ‘pointed’ cat (Siamese pattern). In a forest or grass land habitat, the white coloring would undoubtedly be a disadvantage, and the occasional pointed kitten produced would rarely survive to adulthood. However, suppose there is a climate change, or some of the cat population is driven out of its normal range, and must exist in an area where there is snow on the ground for much of the year. Suddenly, the pointed cats have a definite advantage in surviving the harsh winters, as they blend in more easily with the background, thus being more successful hunters and less likely to become prey themselves.
While an occasional kitten that inherited two pointed genes died in the ‘normal’ habitat, cats that carried a single copy suffered neither harm nor benefit from it. However, when circumstances changed, the pointed kittens had an advantage and increased the incidence of the gene in their gene pool. When pointed cats again wandered into the territory of ‘normal colored’ cats and mated with them, the gene was re-introduced into that gene pool, and perpetuated in the species.
Sorry this is so long, and probably boring! I get carried away.
I have a firm grip on reality - now I can strangle it.
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They can’t have any relevance if they have been disproven by more recent data. For example, do you think that Carter and Carnarvon actually discovered the Tomb of King Tut? Silly fool! No less an authority than famed archaeologist Sir Leslie Manly-Smythe declared in 1892 that “the location of the tomb of the boy king Tutankhamun remains unknown.”
**
Ancient history, so far as science goes. The fact is that the evolution of the vertebrate eye is well-explained in the present day, regardless of what famed evolutionary biologists of the past (or, for that matter, non-experts like Arthur Koestler) have to say.
-Ben
Ok then, thanks for setting us straight. There’s no sense in me quoting Darwin, Huxley, Waddington, or Koestler. From now lets just base our opinions on what Ben the internet guy says. Data? No, that’s ok. We don’t need to see any data.
Besides, I’m not even a biologist so I probably wouldn’t understand it anyway. I do however, have a pretty good grasp of arithmatic and that’s all that’s required to figure out that it takes longer than 3 billion years to bring us from the blue green algae stage to the Ben the internet guy stage using random chance mutations and natural selection as the only drivers.
How does adaptation REALLY work? I believe the most correct answer is, “We don’t know yet.”
“Natural selection is not random, nor does it operate by chance. Natural selection preserves the gains and eradicates the mistakes. The eye evolved from a single, light-sensitive cell into the complex eye of today through hundreds, if not thousands of intermediate steps, many of which still exist in nature (See R. Dawkins, “The Blind Watchmaker”, New York:Norton)” - Michael Shermer, “Why People Believe Weird Things”
-I’m not an expert, but I quote them on TV!
Ben:
LOL! I’m going to have to remember that one.
Phil Saoud
That’s nice. Next time you meat someone who believes that the eye arose from several independent mutations, you can mention that quote to them. The whole point of evolution, however, is that mutatations are never independent; every mutation affect the probability of every other mutation.
You’re compltely missing Ben’s point. The fact that Darwin knew of no explanation for the eye no more means that today’s scientists know of no such explanation than the fact that Manly-Smythe didn’t know the location of King Tut’s tomb meant that the tomb doesn’t exist, or that today’s scientists don’t know where it is.
Really? I don’t remember anything in algebra addressing evolution. Care to share the relevant thereoms?