OK, here is my beef with the evolutionary theory

Great Debates
1

I just want to quickly point out I am not a creationist, I am definitely leaning towards evolution, but here is what I can’t understand.

Let’s say we have a type of animal going along on it’s merry way, and all of a sudden through a random genetic mutation, a couple of these animals inherit a gene making them faster, stronger, taller, etc, but some type of favorable mutation.

Why is it that now, all of a sudden, those with out the gene, are doomed?

They could have lived for possibly thousands of years without this new gene, so just because a few of the animals get it, why are the “weaker” ones now having to say their goodbyes?

If we take a deer for example. Deers without this new mutation have been able to out-run tigers for a long time, and their species has prospered. Why can’t the new deer with the ‘favorable’ mutation live side by side with the “weaker” ones? Seeing as the “weaker” ones have been able to cope fine with what they have?

To say that “weaker” species will eventually die out is like saying that only those at the top of the food chain are going to survive.

Look at this way.

Let’s say a deer gets a favorable genetic mutation, and that deer now becomes very much like a tiger. It passes it’s new gene on to it’s offspring, creating “deers” which run, hunt and kill very much like a tiger.

Are all the deers without this genetic mutation now doomed? No. Because deers and tigers have lived side by side for thousands of years as we very well know.

So, who’s going to have the first swipe?

2

It looks to me like your objection is based on a misunderstanding.

It’s not that everybody will suddenly drop dead. It’s that the new gene(s) will tend to make those who have it more likely to survive.

For instance, somewhere in the depths of time, a species that was later to evolve into a giraffe had some animals in the group that were taller than others. This meant they were able to get to food that was higher up on the trees. This gave them a competitive advantage against others of their kind, who could only graze on lower-level foods. They were more likely to survive and prosper when there were food shortages. This went on for millenia, with the animals getting taller as time went on because it gave them the competitive advantage. Eventually, the species looked like what we now think of as giraffes.

It’s not so much that there was anything particularly wrong about the original species; it’s just that the new one can now exploit a different evolutionary niche, which made them more likely to survive whatever circumstances they happened to find themselves in.

No offense, but your example about deers turning into something like a tiger is pretty much meaningless. It would take a hell of a lot more than a single mutation to turn a herbivore like a deer into a carnivore like a tiger.

3

It doesn’t work this way. Now, granted, I am no expert, but I’ve always been interested in evolutionary theory, and I believe I have a grasp of its basic tenets. And one of them is that species don’t randomly mutate, simply because they have no need to do so. For instance, I will never have sex with a woman to create a child that has wings. Simply because the little guy has no pressing, urgent, life-or-death need for them (and even if he did, well, it takes time for these things to work, but I won’t get into specific numbers because hey-I don’t know any). Species mutate to adapt to their surroundings.

Of course the deer will continue to be able to outrun said tigers, and therefore live. And because of this there won’t be any genetically-advanced deer prancing along, either. Not until these tigers start actively, repeatedly and massively catching these deer will they ever have any need for, or any possibility of, mutation. Or they might simply die out and go extinct.

-H.P.E.

4

David, you appear to have missed my point slightly.

I know how evolution works, how a favorable random genetic mutation gives those particluar species a competitive edge over those without.

My question is why can’t those who DON’T have the favorable mutation continue to live and prosper like they potentially have been doing for thousands of years?

My example about the deer --> tiger was far fetched, I know, but I was using it as an example to show that even if your favorable random genetic mutation turns you in to a virtual superman compared to others of your kind, it doesn’t mean the weaker ones are going to die out. Because as we know, fierce, fast, stealthy, hunting-in-packs tigers live side by side with slower, weaker, deer. Why aren’t the deer dying out when an animal such as the tiger is competing for existance with them?

5

HP Ellison said:

Not quite.

Mutations are, indeed, random. But whether they become generally available to the rest of the population is not. That does depend on whether the mutation is useful. However, there is no way for the organism to know ahead of time if something is useful or not.

While it’s true that you won’t have a child with wings, it’s not because of the reason you give, but because it would take a hell of a lot of mutations to get wings!

But you could have a child with only 3 fingers on each hand. Is this a useful mutation? No. While it might not make a big deal of difference in today’s world, if it had happened a few thousand years ago, that mutation would likely die out in a big hurry.

6

Granted, I am also not an expert either, but from what I have read, any species competing for existence CAN and DO have genetic mutations. Although no animal may not “need” a genetic mutation, if some do happen to inherit a mutated gene which gives them a greater chance of survival, then evolutionary theory says that over thousands and thousands of years, eventually this trait will become common in the species.

7

Hey, my first (semi) simul-post!

High fives all round, David.

8

Doc Moss said:

Ah. Well, the answer is that sometimes they do!

Sometimes species split. The “old” group continue in the niche they had been in before, while the mutated group exploits a different niche. Usually the split is caused by some sort of geographic barrier, though, or else continued interbreeding would mix up their genes enough to keep it from happening.

As for why, in a situation where no split occurs, they don’t continue to live on as they have before, it’s because of several reasons.

First, the environment is not constant. What your species was doing thousands of years ago may have been fine at the time, but things change. Maybe it’s colder now, so those who have mutations that cause a thicker layer of fur are better off. Maybe, as in my giraffe example, there is a problem with the food source, so those who can access other sources are more likely to survive.

Second, with your deer/tiger example, your predators are not standing still either. This could be considered a part of the environment, also, and the end result is the same. If your predators are getting faster, then you need to get faster, too. It’s like an arms race.

That depends on whether you pass those genes down or not and what other side effects they might have. If a deer suddenly develops the ability to process food energy in such a way that it’s not penalized, but can now run twice as fast as the rest, and it passes that ability to its offspring yes, the others will eventually die out. They will fall to predators while the faster ones will not. Just because deer have been living alongside their predators doesn’t mean they never die. I mean, the predators have to eat something or they wouldn’t still be around.

The tiger isn’t competing with them for existence. It relies on them for its existence. If tigers killed off every living deer, it would die off, too. When we speak of one animal competing with another animal, we mean in the same niche. So if another herbivore came into town, it might compete with the deer. If they were faster, hid better, or had some other advantage, it might survive while the deer die out (much like if some of the deer carried a good mutation and others didn’t).

In fact, you might occasionally hear of similar things in the news. Some animal will accidentally get transported to a new environment, and it will end up taking over because it has no natural predators or is better able to take advantage of its surroundings or the like.

9

The main thing you have to remember is that evolution is very slow and gradual.
Let’s take your example with the deer. It’s not as if some deer will be born able to run twice as fast as the others but the increase in speed happens slowly over time. When a herd of deer run away from a tiger, only the slowest are killed while the faster ones will live on to breed. The next generation will then be made up of deer mostly the same speed as the fastest of the previous generation. Some will be faster, some will be slower but again only the slowest will be killed off. This happens again and again over thousands of generations, the average speed of the population increasing all the time.
Meanwhile of course, the slowest tigers are not catching the deer so they starve to death whilst the faster breed. Tigers get faster which means deer must be faster, which means tigers must be faster and so on. This is what drives evolution.

10

HP Ellison:

I think this is going to be confusing to someone, sooner or later, reading this thread, to run across the statement that “species don 't randomly mutate”, but instead “mutate to adapt to their environments”. This is certainly not true of individuals, and it is at the individual level that mutations actually occur. (“species mutate” is akin to “society believes”)

Individuals mutate randomly. Only some of these mutations will “pass along” efficiently, since some of them will not be dominant characteristics genetically, and some will require the interaction of many different genes which won’t necessarily get passed along as a contiguous group. Furthermore, only a few such mutations will be advantageous to survival, and of those that are, not all will be selected for, since circumstances have to make inroads in the population of individuals not sharing those characteristics in order for natural selection to occur.

11

And that, David, is the answer I was looking for.

I suppose this was more a GQ now that I think about it, but evolution threads tend to spiral in to debates so I posted it here.

Thanks for your swift replies.

12

Here is a really good example of the “individual mutatation” vs. “speceis mutatation” issue:

Some 1% of the caucasian popuulation is immune to the AIDS virus. They lack a particular protien receptor on the surface of their cells which the AIDS virus needs to latch onto. This mutation happened some 100,000 years ago, near as anyone can tell (they look at which populations have it and which don’t to get this estimate.) Now, not having this receptor dosent hurt anything–thier are a lot of redundancies in our system–but it dosent help anything either. So this slight, utterly meaningless variation between humans has sort just lain there for a hundred millenia.

Enter AIDS. It is an utter coincidence that this mutation renders one immune, but there it is. Suddenly this old, neutral mutation becomes very positive indeed. If we were a non-technological species, the people with the aids Mutation wold start having more living children, on average, than the people without it. Over time, the rate of people with this mutation would jump from 1% to 100%. (Note that if it were a much faster acting, faster speading disease than AIDS this change could happen very rapidly–that is the idea behind punctuated equilibrium) So see, the mutations always exisit on an individual level. It is not until they become useful that they begin to be prevelant on the species level.

To answer the OP, there have been cases where the “old” and “new” species have co-exisited for years. I read a Gould essay about this once, but I am afriad I dont have a cite (not very helpful, I know). The important thing to remember is the concept of finite resources. In any given enviromental niche, there is only so much food, so much water, so many mates, whatever. Individuals or species that are seeking the same food, water, or mates will inevitably be in compititon, and the ones more suited to the enviroment will take more of hte food, water, and mates, leaving the less suited hungry, thirsty, and childless.

13

I know the OP says the question has been resolved to his satisfaction by David B’s “species do split” explanation (well-written and enlightening as always), but let me add something for the benefit of anyone else reading. I’ll try to explain the OP another way, by using a simplistic thought experiment. (I used a similar example in a previous thread maybe a year ago, about punctuated equilibrium.)

Imagine a valley. High ridges on both sides isolate the valley from neighboring features. The valley’s sole plant life is a type of grass that grows to a certain height.

Living in this grass is a mouselike creature, an insectivore. The mouse’s main predator is a larger animal, like a weasel. The mouse is well-adapted to living in the grass; through thousands of years of adaptation, it grows to exactly the right height that it is hidden in the grass, but it can stand up and look around to check for danger. Its legs are the right length to balance speed and agility in the grass.

Random mutations continuously occur, as they always do. Some mice are born taller, which means they can’t hide in the grass as effectively and get eaten more often, which means they are at a disadvantage for survival. Some mice are born shorter, which means they can’t stand up and look over the grass as effectively, so they can’t identify predators as well; same result. Mutations occur, but the alternative traits are inferior to the existing set of traits, so they never take hold, and the species maintains status quo.

Now imagine a volcanic eruption nearby. The falling ash changes the chemical composition of the soil slightly, and simultaneously the winds that have been temporarily changed by the eruption bring a new type of grass seed into the valley. The old grass doesn’t like the new soil chemistry, but the new grass does, so the new grass replaces the old grass in short order.

This new grass isn’t as tall as the old grass. Immediately, the existing mouse “design” doesn’t work as well, because they’re too big and can’t hide in the grass. (I use the word “design” improperly, I know; this is a simplified example. Just bear in mind it is not intended to convey any sort of conscious or deliberate modification of the mouse’s body structure. I just can’t think of a better word at the moment.) The random mutations continue, though, and the same shorter mouse that previously was at a competitive disadvantage is now suddenly a superior “design,” because it’s the best height for the now-shorter grass. Hence, the “old-style” mouse dies out quickly, and if the “new-style” mouse can reproduce fast enough, it replaces the old mouse in the ecosystem. At this point, they may or may not have speciated; this might be a simple characteristic.

Now change the scenario slightly. There’s a river at the bottom of the valley that separates the two sides. The same grass and the same mouse occupy both sides, because even though they’re separated they have no reason to change.

The volcanic eruption, due to wind patterns, brings ash and grass seed to only one side of the valley. The changes described above occur only on that side. The old grass and the old mouse still survive on the non-changed side. Again, at this point, speciation may or may not have occurred, but the slight difference in the two types of mice is at least the first step toward it. (Speciation, of course, has been extensively covered in other threads, and I’ll leave it alone.)

I know this seems like a silly example, and in many ways it is. A real ecosystem is far more complex, with many more interacting elements. However, the isolated valley is well-known in evolutionary biology; read Privileged Hands: A Remarkable Scientific Life by Geerat Vermeij. He’s one of the world’s pre-eminent experts in mollusk evolution, specifically snails. In the book, he describes his work in the valleys of New Zealand (among other things), where he’s found that the various species of land snail are almost invariably unique from valley to valley, and often from one side of each valley to the other, depending on sun exposure, rain patterns, and the like.

Anyway, I hope this helps further clarify the original question.

14

One assumption underlying all evolutionary theory is that there are never enough resources to go around. A species can always make more members than the environment will support. Therefore, there will always be competition. That’s why you get “survival of the fittest”. The “new” animals can’t get along with the “old” animals because they’re both competing for the same resources. The version that competes better will survive better.

15

Think of the genes which cause the deer’s traits to be flowing in a population over time. Let’s say that 50% of a population has a particular mutation and 50% doesn’t. Normally statistics would dictate that these two groups remain more or less in ballance.

Now as soon as it becomes advantagous to have that mutation, the scales will be tipped slightly so that the deer without the mutation will slowly reproduce less and the mutation will approach 100%. But this is over a period of time, it’s not that the old species of deer will die out, but that they would be more likely to mate with a deer carrying that gene, since those that did survived longer, and therefore it’s children would be more likely to possess the speed and strength.

The gene flows across the entire population, not just the have’s. If you have any finite amount of deer which remains reletively constant, as in a natural balance, the family trees will eventually converge on some distant ancestor, and many will share common ancestors. It’s likely that one of those is a have and one is a have-not, but that doesn’t matter any more because the species has evolved.

16

Another thing to be aware of is that if a beneficial mutation appears, the rest of the species doesn’t go poof and disappear in a puff of smoke. Chance are, the other genotype will survive for several thousand years. However, suppose a mutation makes some deer faster. The ones with the mutation will survive longer, and so they will eat more food (proportionally) than the other deer. That means that the rest of the deer will have less to eat, so some of them will starve. The mutated deer will therefore increase in number the next generation, and the normal deer will increase in number. This means that the normal deer will have ven less food, and so on. After a few million years, most of the normal deer will be gone.

17

I see an interesting bit of unnatural selection in my yard every year. The dandelion flowers that blossom in spring have stems of various heights. I don’t mow as often as I could, and mowing is often triggered by the sight of those long stems. When I mow I am selecting against the taller stems, cutting them off before they can go to seed. By the next fall the only dandelions blooming in my yard have very short stems, below the mower’s cutting height.

The next year the process begins all over—the long stems are out there again. Is this because my yard has been reseeded by foreign dandelions? Probably, since the park across the street is cared for even worse than my yard. Is there an environmental factor that causes dandelions to grow shorter stems in the late summer and fall, rendering my observations worthless? Possibly. Do I have several subspecies of dandelion growing in my yard and the ones with short stems can tolerate my hot and dry summers better? Another possibility.

One thing that I know for sure is that I’m putting down weed killer this spring so this evolutionary headache goes away. But will I, instead, be selecting for dandelions that are tolerant of the weed killer? And how long will their stems be? EEEEEEEEEEEEEEEEEEEK!!!

18

One word dropzone:

Triffids.

19

<aside to wife>

Honey, load the fire pump with seawater.

20

Okay, just one more point…

I also think there is still some debate going on about the details of the “survival of the fittest” and, in particular, the issue of how much “noise” there is in the system. For example, Steven Jay Gould looks at the fossils in the Burgess Shale and has been trying to argue that the line that survived to grow into most all the higher forms that we see today has no obvious advantage over the other lines. (There is probably a more correct biological term than “line” to use here, but I don’t know what it is…family, phylum…?) He thinks the degree of randomness involved may be greater than many people believe.

I am not really qualified to have an opinion on his point-of-view, but I’ll throw one out anyway: I find his argument very interesting, although I am not sure I believe that he can be so sure that the line that survived isn’t somehow “better” adapted than the others. Just because noone has been able to make a compelling argument about why this line is better, it doesn’t mean such an argument doesn’t exist. But, who knows?

At any rate, I guess the long-and-the-short-of-it is that there are some parts of evolutionary theory that are settled and some parts that are less so. And, at least last I heard (and I’m probably going back 10 years now when I saw Gould’s lectures), this issue of the degree of directedness vs. noise is still something that is being hashed out. (Or maybe, at this point, it is fairly settled within the expert community but hasn’t really made it out into the popular understanding yet; I don’t know.)