Question about evolution

[Josephnorwood]

How does macroevolution happen slowly, if the "stems" of those mutations are useless? Does it actually happen faster than I've thought, like in a couple grandchildren later. That would make more sense to me for now. Is it so?

Elaboration:

How can macroevolution happen slowly, if for example, only 0,2% of a wing has to evolve first? That would be useless, so why does the mutation last until it becomes an enough of a wing to actually make any difference?

Or have I just misunderstood how "divides on the species level" happen, and it never does actually happen like that?

Edited August 11, 2015 by Josephnorwood

[Greg H.]

The first thing you have to understand is that "species" is an arbitrary term used by people to classify living things. Nature doesn't give two rat sphincters about our arbitrary definitions.

 

Secondly, developing an entirely new structure is expensive in evolutionary terms. It's a lot easier to take something that's already there, such as an arm, and modify it so that the creature it's attached to performs better and survives more readily in the environmental niche it occupies. Mutations that enhance overall fitness tend to propagate through the species because the members that have it tend to live longer and have more offspring.

 

So you might ask, if we go back to the dim recesses of time, where did that first arm/leg/wing come from? Most likely from a fin on a fish-like creature - where developing a small fin at first might indeed offer an advantage over no fin at all in terms of stability. Fins gradually became longer, then as creatures moved onto the land, the developed more specialized functions for walking, running, grasping, and flying. If you look at, for instance, a whale's flipper, it has the same basic bone structure as a human hand, an eagle's wing, or a bear's paw (five "finger" bones converging into a "palm" connected to a shorter or longer appendage that we can call an arm, a wing, or a leg (or a flipper).

[swansont]

The first thing you have to understand is that "species" is an arbitrary term used by people to classify living things. Nature doesn't give two rat sphincters about our arbitrary definitions.

 

Secondly, developing an entirely new structure is expensive in evolutionary terms. It's a lot easier to take something that's already there, such as an arm, and modify it so that the creature it's attached to performs better and survives more readily in the environmental niche it occupies. Mutations that enhance overall fitness tend to propagate through the species because the members that have it tend to live longer and have more offspring.

 

So you might ask, if we go back to the dim recesses of time, where did that first arm/leg/wing come from? Most likely from a fin on a fish-like creature - where developing a small fin at first might indeed offer an advantage over no fin at all in terms of stability. Fins gradually became longer, then as creatures moved onto the land, the developed more specialized functions for walking, running, grasping, and flying. If you look at, for instance, a whale's flipper, it has the same basic bone structure as a human hand, an eagle's wing, or a bear's paw (five "finger" bones converging into a "palm" connected to a shorter or longer appendage that we can call an arm, a wing, or a leg (or a flipper).

 

A whale, though, is an example in the other direction. An appendage of a land creature adapting to life in the sea.

http://evolution.berkeley.edu/evolibrary/article/evograms_03

https://en.wikipedia.org/wiki/Evolution_of_cetaceans

[Delta1212]

 

How does macroevolution happen slowly, if the "stems" of those mutations are useless? Does it actually happen faster than I've thought, like in a couple grandchildren later. That would make more sense to me for now. Is it so?

Elaboration:

How can macroevolution happen slowly, if for example, only 0,2% of a wing has to evolve first? That would be useless, so why does the mutation last until it becomes an enough of a wing to actually make any difference?

Or have I just misunderstood how "divides on the species level" happen, and it never does actually happen like that?

 

There seem to be a couple of misconceptions embedded in this.

 

For starters, one species doesn't start morphing into another in quite the way your post seems to be implying. The next "step" in evolution doesn't "have wings" and therefore the species starts growing wings. The line between species is a lot blurrier and how one becomes another (or many others) is rather directionless except insofar as it's guided by who reproduces the best.

 

Essentially, there is never a "useless stem" at any point in the evolutionary process. Every step along the provides some advantage over what came before it, which is how it spread and became a step along the way in the first place. If some creature randomly sprouted half a wing, it wouldn't be an intermediate stage in the evolutionary process. It would be weighed down by a useless appendage and probably die, and that would be the end of that. What actually happens is a bit more subtle. Let's look at a hypothetical example, starting with some small, bipedal dinosaur-looking creatures and see how a wing might evolve.

 

So, we're starting with a creature that has two arms, two legs, probably a tail for balance and I'm imagining a narrow snout with some sharp teeth. How is thins thing going to get some wings? Well, for starters, it's not going to sprout some wing buds. As mentioned above, evolution tends to co-opt existing structures rather than forming them completely from scratch, both because that is less energy intensive and, frankly, it's just far more likely that you're going to see a small change in an existing body part that makes it work better than an entirely new structure sprout fully functional out of nowhere. It's not actually physically impossible, but it is slightly more likely that you would win every nationwide lottery for the rest of your life. Anyway, for the purposes of this example, we're going to use the arm, because that seems to be a pretty popular choice for turning into a wing in real life.

 

So, founder of our new winged species is going to be a little dinosaur creature that is born with what, under the vast majority of circumstances, would be considered a birth defect. It has a little flap of skin under its arms, like someone with webbed toes or feet. Usually, that would either be a disadvantage (that flap provides a potential sources of infection if it gets torn or injured) or just be a bit of useless skin, but in this particular case, because of whether the flap is and the body plan of the creature that has it, it discovers that if it stretches it's arms out, that flap of skin acts as a bit of an extra stabilizer when running. So now it can run just very slightly faster than it could have otherwise without stumbling out of control. That gives it enough of an advantage that it manages to outrun any predators and catch enough food to eat and eventually have children.

 

And all the kids, or maybe not even all of them, but a number of them, being descended from that first creature, have little skin flaps themselves. And they take advantage of them, and the creatures wit skin flaps run faster and survive better than those without. And eventually, over many generations and many, many years, all of the creatures will have either mated with the descendents of that first creature with skin flaps, or they will have been outcompeted, as the ones without them won't have been able to keep up and been eaten or missed out on getting food that the ones with skin flaps caught.

 

So now all of the creatures have skin flaps, and as with any population, they will all vary a little bit. Some of the flaps will be thicker, some thinner, some bigger, some smaller. And these different sizes and shapes will vary in their effectiveness. And the ones with the most effective shapes will be able to reproduce more, in the same way that simply having them allowed the first ones to do better, and so these flaps are run through the filter of natural selection. And as they trend towards allowing faster, and more stable running, eventually it gets to a point that one of them is born with a skin flap that is just the right size and shap that they can glide a little bit. Or maybe it doesn't even qualify as a glide. Maybe it's just a slightly longer jump. But now they can jukp farther, and stay higher for longer than any of the others.

 

And if, for example, some of their food includes flying insects, that could prove useful for catching escaping flies that one of the others would fall just short of reaching. Or it could allow them to get around obstacles or clear gaps that are just a little too difficult for those who can't jump as well. And so this one manages to take advantage of the way their skin flap works and again is a little more successful, and has more kids and that particular size and shape becomes more common in the population over the course of generations.

 

And as the number of long jumpers grows, so does the variation of their own skin flaps. Some are bigger or thicker or different shapes, and some of those shapes are better for jumping than others. And of course, the creatures themselves all come in different sizes or shapes. Some are heavier or lighter. And some of those creatures find that they can take better advantage of their jumping ability than others. So you get the shape of the proto-wing as well as the shape of the creature itself converging toward one that is better and better at jumping as the best jumpers continue having children and the new body plans are all based on those most successful jumpers.

 

Until eventually, one is the right shape and size and weight and everything else that it can legitimately glide. And that opens whole new sources of food and escape from danger that further enhances that gliding ability in the same process described above where the best gliders have the most kids and the variation among the children results in some being slightly worse gliders but some being slightly better, until eventually a body plan has been selected for that allows for longer and longer gliding until a long glide and actual flight are essentially indistinguishable, and now that arm with little skin flaps has become a full fledged wing.

 

Over the course of many, many, many generations. Just look at the bone structure of a bat wing. You can see the arm and fingers of the original furry animal that was its ancestor which have since thinned and lengthed to become the scaffolding for its own skin flaps, allowing it to fly.

[overtone]

Others have been more thorough, here's the short version:

 

 

How does macroevolution happen slowly, if the "stems" of those mutations are useless?

Short: They aren't useless.

 

 

 

 

Or have I just misunderstood how "divides on the species level" happen, and it never does actually happen like that?

Short: Yes

 

Comment: get your information about evolutionary theory from competent evolutionary theorists, people who use the theory.

 

The question you asked is one of the standard set of bs harassment questions that show up on forums like this every couple of months, posted by naive young folks who have been sent out into the big world by organized groups with a hidden and not very good agenda.

 

If you got that question from somebody, and were sent to some place like this to post it, go back to whoever did that to you and ask for some clarification.

Edited August 12, 2015 by overtone

[CharonY]

 

Essentially, there is never a "useless stem" at any point in the evolutionary process. Every step along the provides some advantage over what came before it, which is how it spread and became a step along the way in the first place. If some creature randomly sprouted half a wing, it wouldn't be an intermediate stage in the evolutionary process

 

While that is partially true for wings as the intermediates are still functional appendages, it should be noted that changes do not need to be beneficial themselves. As long as they are not heavily selected against, they may persist and even spread throughout a population either by chance (e.g. drift) or by co-selection, for example.

[overtone]

 

 

- - it should be noted that changes do not need to be beneficial themselves. As long as they are not heavily selected against, - - -

If the "changes" are the rudimentary beginnings of some new feature, as the OP indicates, then they pretty much have to provide benefit to counter their cost: the resources expended in manufacturing them and maintaining them and repairing them, the risks involved in carrying them around, extra cancer vulnerability and similar mischance probabilities, and so forth.

 

They add to the overhead, at a minimum. They need to add to the income, to avoid being selected against.

[CharonY]

If the "changes" are the rudimentary beginnings of some new feature, as the OP indicates, then they pretty much have to provide benefit to counter their cost: the resources expended in manufacturing them and maintaining them and repairing them, the risks involved in carrying them around, extra cancer vulnerability and similar mischance probabilities, and so forth.

 

They add to the overhead, at a minimum. They need to add to the income, to avoid being selected against.

 

 

That is not typically how things happen. Mutations are typically neutral or sometimes detrimental, beneficial ones are very rare.

For example, mutations in enzymes tend to happen in duplicated genes as they would not be selected against (or, as you put it, add overhead). The cost of duplication is, as a whole often not very high (i.e. only weak or no selection). For example, in organisms with bipedalism, changes in the arm strength is probably not associated with a high cost. Over time changes may accumulate that significantly change its structure from the precursor.

[MonDie]

 

That is not typically how things happen. Mutations are typically neutral or sometimes detrimental, beneficial ones are very rare.

For example, mutations in enzymes tend to happen in duplicated genes as they would not be selected against (or, as you put it, add overhead). The cost of duplication is, as a whole often not very high (i.e. only weak or no selection). For example, in organisms with bipedalism, changes in the arm strength is probably not associated with a high cost. Over time changes may accumulate that significantly change its structure from the precursor.

An organism only needs to be good enough, not perfect. Do you think this is partly why genetic variation is tolerated?

I'm reminded of the concept of mutation load. http://www.nature.com/nrg/journal/v16/n6/full/nrg3931.html

[overtone]

 

 

That is not typically how things happen. Mutations are typically neutral or sometimes detrimental, beneficial ones are very rare.

Which is why the evolution of a new structure as described in the OP is rare.

 

For example, mutations in enzymes tend to happen in duplicated genes as they would not be selected against (or, as you put it, add overhead).

The OP described the situation at issue as one of rudimentary changes in morphology acting as nascent new structure, not changes in the genetics only.

[CharonY]

Change in genetics are are what causes inheritable morphological changes. OP specifically mentioned wings. In a number (if not most) of species the evolution is speculative, hence the insistence on immediate positive selection is unfounded. Most known elements, however, point to outgrowths of wings from a variety of structures (such as gills or arms) and not some completely novel, additional structures.

[jamieoverton727]

Macroevolution refers to major evolutionary changes over time, the origin of new types of organisms from previously existing, but different, ancestral types. Examples of this would be fish descending from an invertebrate animal, or whales descending from a land mammal. The evolutionary concept demands these bizarre changes.

[Sorcerer]

 

How does macroevolution happen slowly, if the "stems" of those mutations are useless? Does it actually happen faster than I've thought, like in a couple grandchildren later. That would make more sense to me for now. Is it so?

Elaboration:

How can macroevolution happen slowly, if for example, only 0,2% of a wing has to evolve first? That would be useless, so why does the mutation last until it becomes an enough of a wing to actually make any difference?

Or have I just misunderstood how "divides on the species level" happen, and it never does actually happen like that?

 

Mutations don't have to be useful to survive, they only need not be harmful. If the mutant is equally as reproductively fit as the non mutant, those new genes have a chance to stay in the population. Various mechanisms like genetic drift can cause those new genes to be more abundant even though there wasn't any real advantage to them. It is then possible for another mutation to cause, by changing the gene again, or adding another gene to it, the previous neutral mutation to become advantageous, this could be in a short time or in a long time, as long as the gene is in the population to be added to or modified. This by the way can (but is less likely each time) carry on many times, adding neutral mutations cumulatively untill eventually they add up with the ultimate mutation to form something advantageous.

 

The problem with neutral mutations is that genetic drift can also go the other way, and the genes can simply disappear from the population.

But it must be remembered when talking of chance and life, that there have been billions of years and many times that generations of life since its origin, which means there have been that many chances, even unlikely things occur sometimes if there are enough events. But, since it is the chance of another mutation, (in the same or another gene), and the chance of the original required, they are far less likely to lead to advantageous adaptions than the other possibility, which is:

 

Each mutation confers a small advantage, and each sucessive mutation builds on that adding a little more of an advantage. These types of mutations spread through the gene pool faster because they are actively selected for, the more reproductively sucessful in each sucessive generation outcompete the less sucessful untill more of their DNA is in the gene pool.

 

It is also possible to have a combination of these 2 processes working on the same adaption. So neutral mutations which effect advantageous mutations can stay around in the genepool, another mutation can occur which otherwise wouldn't be advantageous unless in the presence of the extra neutral one, the neutral one spreads because of the new mutations mutual advantage. And there could be any kind of combination of these mutation timelines.

 

So in the case of the wing, it would have had a function prior to that which was useful, the ancestors of birds are dinosaurs, they had arms for doing various things with which gave them an advantage, arms became wings. Genes for arms arms added with a mutation that gave them feathers could provide insulation from cold, or they could help attract mates, or if they didn't do much at all, but didn't hurt much at all, could also spread.

 

So in essence macroevolution can happen in any time frame, but it is chance, selection, genetic drift and cumulative adaptive or neutral mutations which creates new forms.

 

 

[overtone]

 

 

The evolutionary concept demands these bizarre changes.

It doesn't demand them, it explains them.