how did whales evolve

[andy b]

Ive been trying to get to grips with the theory evolution but i cant understand how whales evolved or why they have not evolved gills.From what i can gather they evolved from land mammals and these land mammals must of at some point evolved from sea animals that once had the ability to breath underwater so why have they not re evolved gills surely that would suit them better.It seems as a species they have gone from gills to lungs two completely different organs but they cant go from lungs to gills an organ there ancestors must have had at some stage.Id appreciate any thoughts on this but i request you keep it simple as its not something im an expert in.

 

[Nithavela]

First you need to understand that evolution does not aim for "optimal", but for "able to reproduce". And breathing by lungs is more then enough for them to reproduce, evidently. Also, they may not have changed that they need to breathe trough luns, but they developed blowholes and the ability to hold their breath for a very long time.

 

[Shemjaza]

Evolution can only work with individual steps that either help or don't hurt the species survival.

Land animals evolved from sea creatures who lived part of their time on land, so the first lungs worked in conjunction with gills not instead of. (The modern lungfish and mud skippers are examples creatures who live on the borderline of land and water.)

While the ability to breath water directly would probably be an advantage to sea mammals, instead they have developed the ability to hold their breath fora very long time.

Flying mammals like bats would probably be better off with flight feathers... but they didn't have basic feather to work from, so giant webbed hands is what they use.

Evolution is all based around little steps and being good enough to survive, this means many different techniques and systems have developed to solve similar problems. Also in other situations you can get the same system developing from a different base point.

 

[juvenissun]

First you need to understand that evolution does not aim for "optimal", but for "able to reproduce". And breathing by lungs is more then enough for them to reproduce, evidently. Also, they may not have changed that they need to breathe trough luns, but they developed blowholes and the ability to hold their breath for a very long time.

Please explain why should it be so. I think it is only an excuse of a failing theory.

 

[[serious]]

Ive been trying to get to grips with the theory evolution but i cant understand how whales evolved or why they have not evolved gills.From what i can gather they evolved from land mammals and these land mammals must of at some point evolved from sea animals that once had the ability to breath underwater so why have they not re evolved gills surely that would suit them better.It seems as a species they have gone from gills to lungs two completely different organs but they cant go from lungs to gills an organ there ancestors must have had at some stage.Id appreciate any thoughts on this but i request you keep it simple as its not something im an expert in.

Evolution doesn't chase after the theoretical optimal, but rather the best next step. Sure, whales, if you go back far enough, came from bony lung fish. But at the time they were returning to an aquatic environment, they had lost those gills, fins, etc. As staying in water longer became beneficial, the best next step was adjusting lung capacity and oxygen efficiency. After all, they had lungs, but no gills.

Thing of this by way of analogy. Let's say you own a car. It's a good car that does everything you need it to. YOu move into a city and no longer need that car, so eventually, you sell it. That's fine, you don't need a car anymore. A few years pass and you move back out to the country. Do you get the exact same car you had previously sold or do you look for the best car you can get right then?

 

[essentialsaltes]

Ive been trying to get to grips with the theory evolution but i cant understand how whales evolved or why they have not evolved gills.

I'm not an expert either, but the accidents of evolutionary history can be hard to unwind. For the first fish coming on land, they found they could gulp air into their swim bladders to get a little extra oxygen, and stay on land a little longer. And as they 'practiced' that, the swim bladders got better at delivering oxygen, ultimately becoming lungs.

For a land creature to go back underwater, there's no way for them to get a little extra oxygen out of the water. They don't have gills anymore, and you'd drown if you got water in your lungs. It's much easier to just hold your breath, and practice holding your breath. And that's the easy path that whales have taken. As others have said, it's not optimal. They still have to come back to the surface for air. But evolution does not and cannot aim for the perfect solution. Generally speaking, it aims for 'a little bit better'. And that constrains the paths that evolution can take.

 

[[serious]]

I'm not an expert either, but the accidents of evolutionary history can be hard to unwind. For the first fish coming on land, they found they could gulp air into their swim bladders to get a little extra oxygen, and stay on land a little longer. And as they 'practiced' that, the swim bladders got better at delivering oxygen, ultimately becoming lungs.

For a land creature to go back underwater, there's no way for them to get a little extra oxygen out of the water. They don't have gills anymore, and you'd drown if you got water in your lungs. It's much easier to just hold your breath, and practice holding your breath. And that's the easy path that whales have taken. As others have said, it's not optimal. They still have to come back to the surface for air. But evolution does not and cannot aim for the perfect solution. Generally speaking, it aims for 'a little bit better'. And that constrains the paths that evolution can take.

My understanding is that lungfish predate swim bladders. Swim bladders are modified lung like structures.

EDIT: yup, lungs were an existing structure homologous to the swim bladder.
http://en.wikipedia.org/wiki/Swim_bladder

 

[essentialsaltes]

Like I said, I'm not an expert. I guess if you replace 'swim bladder' with "simple sacs connected to the gut [that were not yet either modern lungs or swim bladders]," my point remains.

 

[andy b]

bur surely it would be easier to develop something you once had rather than a complete new organ like lungs.Plus how come not a single branch of sea mammals have shown any movement in that direction over the alleged millions of years.Surely a type of whale or porpoise ETC would have grasped this advantage it flies in the face of reason with all the mutations that go on.

 

[essentialsaltes]

bur surely it would be easier to develop something you once had

How could that be easier than holding your breath?

rather than a complete new organ like lungs.

As pointed out, lungs came from preexisting sacs. Evolution often works by finding a new use for an existing structure. For instance, some scientists have hypothesized that gills evolved into structures in the ears of mammals. Even if evolution could 'run backward', it might not be advantageous to start reforming gills if it means that you go deaf.

 

[andy b]

thats probably the case but i find it strange that a species that started in the water at one point ends up back in the water but not as well adapted....it would be like us starting to swim developing gills then deciding the water is to cold so go back on land but keeping the gills it just doesn't seem advantageous.I mean why would a mammal decide to go back in the water for good anyway did mutation decide to lose the legs and grow a flipper it just doesn't add up to me. flipper to legs to flipper but not gils to lungs to gils can you see my point why one adaption and not the other.What are the odds of mutating from flipper to legs then back to flipper and why have no other species done this kind of switch.

 

[Seipai]

thats probably the case but i find it strange that a species that started in the water at one point ends up back in the water but not as well adapted....it would be like us starting to swim developing gills then deciding the water is to cold so go back on land but keeping the gills it just doesn't seem advantageous.I mean why would a mammal decide to go back in the water for good anyway did mutation decide to lose the legs and grow a flipper it just doesn't add up to me. flipper to legs to flipper but not gils to lungs to gils can you see my point why one adaption and not the other.What are the odds of mutating from flipper to legs then back to flipper and why have no other species done this kind of switch.

Who says no other species have done this? Look at penguins, look at seal, look at manatees. Quite a few different species have made the "backwards" trip.

 

[Paulos23]

thats probably the case but i find it strange that a species that started in the water at one point ends up back in the water but not as well adapted....it would be like us starting to swim developing gills then deciding the water is to cold so go back on land but keeping the gills it just doesn't seem advantageous.I mean why would a mammal decide to go back in the water for good anyway did mutation decide to lose the legs and grow a flipper it just doesn't add up to me. flipper to legs to flipper but not gils to lungs to gils can you see my point why one adaption and not the other.What are the odds of mutating from flipper to legs then back to flipper and why have no other species done this kind of switch.

What is not well adapted about them? They seam very well adapted to living in the the ocean.

 

[essentialsaltes]

I mean why would a mammal decide to go back in the water for good anyway

Maybe to escape predators. Maybe to go after a better source of food.

I mean, maybe a weasel found that there was good food growing in shells down under the water, so it decided to spend more and more time in the water. And the better swimmers could get more of the food and swim deeper. And to swim deep, it would be advantageous to have webbed feet for swimming. And after a time, you have a sea otter. It's a member of the weasel family, but it has entirely webbed hind feet, and lives most of its life in the water.

flipper to legs to flipper but not gils to lungs to gils can you see my point why one adaption and not the other.What are the odds of mutating from flipper to legs then back to flipper and why have no other species done this kind of switch.

Now, to be careful here, fish do not have flippers. They have fins. The path of evolution leaves behind baggage that's not easy to get rid of. One thing you notice is that fish have vertical tails for providing thrust in swimming. Whales and dolphins have horizontal flukes for providing thrust in swimming. Obviously there are similarities between fins and flukes, but they are not quite the same thing, and they followed different evolutionary paths to create these different structures.

 

[andy b]

Who says no other species have done this? Look at penguins, look at seal, look at manatees. Quite a few different species have made the "backwards" trip.

im classing manatees with whales,and your right paulo they are adapted but in an ice age where vast amounts of sea are covered in ice surely a species that can breath underwater would have a massive advantage...as for penguins the still look like birds just more adapted plus they live on sea and land.Whales as far as i know live purely in water if penguins lived purely in water you could compare them.

 

[andy b]

Maybe to escape predators. Maybe to go after a better source of food.

I mean, maybe a weasel found that there was good food growing in shells down under the water, so it decided to spend more and more time in the water. And the better swimmers could get more of the food and swim deeper. And to swim deep, it would be advantageous to have webbed feet for swimming. And after a time, you have a sea otter. It's a member of the weasel family, but it has entirely webbed hind feet, and lives most of its life in the water.

but sea otters like seals etc still go on land and give birth on land.Ive only just thought of that at what point could giving birth to air breathing offspring underwater be deemed advantageous surely the survival instincts of the young the parental instincts of the parent and the actual mechanics of the body would all have to have developed at the same time or they would have died out.

 

[essentialsaltes]

Ive only just thought of that at what point could giving birth to air breathing offspring underwater

The fetus/baby in the womb is not air breathing. In fact, many people have noted that the amniotic fluid has some similarities to seawater. Why do land animals have seas in their wombs?

Some people today even prefer to have 'water births' where the baby is delivered underwater. I remember there was a fad for it in Russia some decades ago. Whether it's a great idea or not, I don't know, but it shows that air breathing babies can be born underwater. All of these adaptations don't have to happen simultaneously.

 

[andy b]

The fetus/baby in the womb is not air breathing. In fact, many people have noted that the amniotic fluid has some similarities to seawater. Why do land animals have seas in their wombs?

Some people today even prefer to have 'water births' where the baby is delivered underwater. I remember there was a fad for it in Russia some decades ago. Whether it's a great idea or not, I don't know, but it shows that air breathing babies can be born underwater. All of these adaptations don't have to happen simultaneously.

but the ocean is full of vicious predators and more so eons ago.but do get my point that the whales body and instincts on how to nurture would have to have mutated at the same time.Its things happening at the same time which i cant get my head around in evolution like that spider and flower that look the same i mean what are the odds it would be like a human being born looking like a chair.

 

[Mr Clean]

Please explain why should it be so. I think it is only an excuse of a failing theory.

Why does there have to be a reason? I know religious people think there has to be a reason for everything, but that's actually now the real world works. Evolution is change due to random mutation. That's all it is. There is no reason for what mutations happen or when.

 

[Mr Clean]

but the ocean is full of vicious predators and more so eons ago.but do get my point that the whales body and instincts on how to nurture would have to have mutated at the same time.Its things happening at the same time which i cant get my head around in evolution like that spider and flower that look the same i mean what are the odds it would be like a human being born looking like a chair.

No, the instincts do not have to "mutate" at the same time that the body does. There's nothing that says that the genes that affect a particular instinct are the same ones that affect how a creature breathes or gives birth or sees or does anything in particular.

As to your spider comment, don't think of the end result. Think of how it came together. You have a species of plant that produces a yellow flower. A spider that has a random mutation that gives it almost the same yellow color is born. It catches a lot more food when it sits on the yellow flower because it is hard to see. It even catches more than any of the regular brown spiders that make up the rest of its species. This allows it to be more successful than other spiders sitting on yellow flowers or anywhere else. This allows it to breed, more yellow spiders are produced. Maybe some of them try to sit on red flowers, and they starve or have to move. The ones that sit on yellow flowers continue the success of its parent. The yellow ones on yellow flowers breed more, and still more are produced. The end result is that the species ends up being the yellow variety because that is the most successful way to collect food.

This is evolution. Not every flower in the world has a spider that looks just like it. Only those that had a random mutation that happened to match the color of a local species of flower and are successful with that mutation thrive.

It's random. It just happened. No reason for it.