Thread: evolution of dolphins

were dolphins around when the megalodon was still alive? if so, is it possible that their eco-location system was different/ a more powerful hunting tool? or was there a larger cousin of the dolphin that maybe was smart enough to outwit the much larger sharks??

Certainly, there would have been some ancestor of the dolphin present at this time - the dolphin and its ancestors predate megalodon. As for more advanced echo-location, I think such a trait would have remained.

In fact, it is thought that megalodon did, in fact, prey on cetaceans, including dolphins, and whale bones have been recovered with megalodon tooth marks on them.

I don't think megalodon was ever present in sufficient numbers to be an extinction threat to dolphins or their ancestors. That said, the extinction of a number of cetacean species around 1.5 million years ago is considered a possible cause/contributing factor for the extinction of megalodon. If this is the case, then the survival of dolphins is most likely because they were able to survive in the arctic/antarctic circles, where the water was too cold for cold-blooded megalodon.

so you are implying that dolphins probably survived because of the randomness of traits and Darwinism;
and that the Dolphins intelligence never came into play?

i doubt whether intelligence is much of an issue when you're surfing and a white shark happens to take a fancy to you ...

as you may be aware they come from your blind corner and you're more likely to feel the shark's teeth before you see him

living in groups that look after one another may be more of protection than individual intelligence

The modern Great White preys on seals rather than dolphins. It is an ambush predator, launching itself upwards towards a seal silhouette when it passes overhead.

It is rather likely that Megalodon was similar. However, the great size of Megalodon would seem likely to be an adaptation for preying on very large prey. I suspect that dolphins and seals were not often prey, since they would have been too alert and too agile. However, the very large size of Megalodon makes it ideal to prey on whales.

Of course, the young of Megalodon would have had to tackle smaller prey, such as fish, squid, and small marine mammals.

The teeth, like that of the Great White, are designed to cut chunks out of prey, rather than hold onto prey. The modern White Shark uses this to mortally wound its prey, while it swims off to wait for the prey animal to die, before swimming back to eat it at its leisure.

Megalodon may, or may not, have used such a technique. As far as I know, it may even have attacked large prey, to take a mouthful and swim off, leaving the prey animal, like a large whale, to slowly recover.

That could be disproved if we find bones in their stomachs. Disproved as primary M.O. I mean.

This was a funny read:
http://www.nwf.org/nationalwildlife/...&articleid=991

Whether the Farallon sharks recognized the killer whales by sight or by sound, the presence of the whales did appear to trigger their hasty exodus. Humans fear the great white shark as the ultimate predator; the sharks may perceive their rank differently.

It seems killer whales make sushi out of great whites.

Eventually the dolphin lineage did give rise to a shark killer.

By 2.5 million years ago, large, orcalike dolphins appeared, and C. megalodon died out. Some paleontologists think this was no coincidence: The ancestors of today’s killer whales may have outcompeted C. megalodon for the top spot on the oceanic food chain. Perhaps the white shark survived because it was less specialized than C. megalodon. Or maybe it survived because it dodged large, dangerous dolphins as assiduously as it had always avoided C. megalodon.

One killer whale that's been well studied off California, appears to kill sharks exclusively. Her speciality is great white, and she eats only the liver. She must dispatch a lot of sharks to maintain that lifestyle.

To pong

There will not be any fossils of bones in any Megalodon stomach. The reason is that this shark has a skeleton of cartilage which does not fossilise. Barring some strange accident of fossilisation - a very rare event - we have only teeth to draw conclusions from.

This lack of data leads to lots of speculation, like the above post on Megalodon dying due to competition from proto-orca. It might be true. It might not. All good fodder for speculation.

Originally Posted by skeptic

we have only teeth to draw conclusions from

Then compare its teeth to those that routinely crunch bone. If megalodon's like the cookie-cutter shark an unusually small fraction would be chipped or blunted.

I happen to be a tooth expert and those teeth are not made for crunching.

As in no way.

Would you say they're too fragile for general scavengery, like cleaning carcasses? I'm thinking that if Megalodon's a whale nipper it would rarely bite bone. Thin knives are better.

The nice thing about the shark dentition is the constant replacement of teeth, which is absent in the mammalian dentition.

Another feature is the 'primitive' attachment of the tooth. The teeth of sharks don't really have proper roots. They are basically attached directly to the jaw "bone" (read cartilage in case of sharks, but the same system is present in most animal groups, such as 'bony fish, and most reptilians).

It's a nice attachment but it cannot endure much stress that is usually associated with a grasp and shaking the prey. The way for instance killer whales shake a sealion out of its skin.

Therefore sharks lose teeth regularly. But then again, they are replaced.

Most reptilians have the same kind of tooth attachment straight to the jaw bone. The exception is the crocodile which has a root very similar to ours, with a specialized connective tissue between the surface of the tooth root and the surrounding bone. The connective tissue acts similarly to a shock absorber. That's probably why crocodiles can do the rolling thing with their prey (hold the prey and roll till a piece tears off). It doesn't really matter if they lose a tooth once in a while, since they also have constant replacement of teeth.

However in mammalian species the teeth are very different in the sense that there are never more than 2 successive dentitions. Once you lose the second generation you are not going to get a new one.

So sharks can definitely nibble and scavenge and even tear and roll. It just means they will lose more teeth. But that can be compensate for by the replacement.

The only problem is that it takes a while for teeth to be replaced. So if the rate of attrition is greater than that of replacement a shark will have a problem.

so have we established that these sharks went after creatures smaller than whales

i doubt whether intelligence is much of an issue..... living in groups that look after one another may be more of protection than individual intelligence

Isn't intelligence one of the rarest things around..? i would think that a super-predator would be an excellent influence on the development of some kind of brains in the early dolphin ancestors.

Originally Posted by RAWasFCK

so have we established that these sharks went after creatures smaller than whales

Not yet. Even spuriousmonkey wouldn't speculate on what it bit... just that it didn't specialize in crunching bone.

If Megalodon bit large whales I think it would want to cut (not rip) out a plug of blubber, and accomplish that in one swift motion. So the teeth are best arranged neatly in rows, not staggered and jagged as the gripper maws of scavenging sharks are. And if it was a whale killer it would want injurious fangs.

Originally Posted by RAWasFCK

i doubt whether intelligence is much of an issue..... living in groups that look after one another may be more of protection than individual intelligence

Isn't intelligence one of the rarest things around..? i would think that a super-predator would be an excellent influence on the development of some kind of brains in the early dolphin ancestors.

I like to think I'm smarter than the average bear, but confronted with a lion, or a great white, or some other large predator, I'd be pretty screwed.

NO, not if you had grown up doing it to survivie, and your parents before you, and their parents before them. Thats how Native americans did it, why wouldn't it go the same way for dolphins, on their road to develop intelligence?

Dolphin intelligence probably evolved by a different route to human intelligence. Humans are tool users, and dolphins are not. Personally, I suspect that dolphin intelligence is strongly linked to dolphin sociability.

Imagine a situation where dolphins had to work together, with excellent communication, to thwart the threat of a super-predator. Would this not be a strong driver of the evolution of a smarter dolphin?

Here's my favourite clever dolphin clip: Dolphin play bubble rings

Apparently they just do this. Watch closely at 0:45. The dolphin spins a ring and seems to study the outcome. This is fluid dynamics, learned through experiments. I doubt there's a human on Earth who could guess just when or how that ring suddenly disintegrates.

@Skeptic. I agree about the group coordination. Another thing, is that understanding fluids in real-time demands serious brainpower. Watch a toddler walk with a cup of juice.

Ever seen a school of fish? Their coordination is amazingly intricate. Yet they are pretty much stupid.

Originally Posted by spuriousmonkey

Ever seen a school of fish? Their coordination is amazingly intricate. Yet they are pretty much stupid.

isn't that the same as with flocks of birds ? the application of a number of local rules of behaviour for each individual bird gives the impression that the flock as a whole has a dynamic of its own

both schools of fish and flocks of bird are a prime example of apparent organisation at a higher level emerging from the mindless application of local rules

Indeed, so complexity in group behaviour doesn't indicate intelligence, nor requires it.

Just look at facebook. Millions of mindless primates exchanging messages and yourtube videos in a complex social network.

There is an enormous difference between a school of fish mindlessly imitating each other, and a pod of dolphins working together to bubble net prey, or to harass a predator.

i think that what spurious was trying to say is that not all group behaviour is an indication of intelligence

Originally Posted by skeptic

There is an enormous difference between a school of fish mindlessly imitating each other, and a pod of dolphins working together to bubble net prey, or to harass a predator.

Right. But did these particular applications of intelligence drive the evolution of dolphin intelligence? I argue that dolphin intelligence expanded quantitatively into the open-ended fields of spacial acuity and fluid dynamics. By developed a high volume of flexible intelligence, originally for those purposes, they happened to exceed the threshold for qualitatively radical applications of intelligence. Their cup runneth over.

Pong

I must disagree. If that were true, then why is it that herbivorous marine mammals are so stupid? They must also cope with fluid dynamics. Yet dugongs and manatees show no signs of intelligence. Even the mysticete whales show little sign of any advanced intelligence.

However, the carnivorous and predatory marine mammals, such as seals, dolphins and sperm whales are all smart. Not all equally smart of course, with bottlenose dolphins probably leading the bunch, closely followed by Orca.

The smartest of this bunch are all social animals, that work together.

Analogy of what I'm saying about dolphin intelligence and its many applications (including cooperative hunting): Primates are dexterous. Some even use tools. Why? Did they evolve dexterity to use tools? No, they began to evolve dexterity only for grabbing branches. After that reached a certain threshold, dexterity happened to enable grasping food. So they evolved greater dexterity to better grasp food. Then another threshold they happened into: pulling things apart. So more dexterity, for that purpose. Now at this point, their dexterity "runneth over" enabling all sorts of manipulations, really only limited by intelligence.

I've had limited success in teaching a park raccoon to open zippers on bags and purses. It studies what I'm doing with the cookie in the bag, but lacks the empathy to mimic.

Notice how your own intelligence flows from spacial and mechanical metaphor. You say bottlenose dolphins probably leading the bunch, closely followed by Orca. I suppose a dolphin would grasp that metaphor quite naturally, but as for "grasp"..? Hmmm.

Pong

I agree that primates evolved dexterity and then applied it to tool use. However, I have a personal theory that human forebears went one very major step further. They became so dependent on tool use that the faculty to use tools became a powerful driver of evolution in its own right. That is, once pre-humans became dependent on tools, the best tool users had a selective advantage, and evolution was driven towards increasing ability to use tools.

This led to upright stance, big brains, dexterous fingers, strong legs and weaker arms. The applications of tool use and simple technology led to loss of body hair (if you got clothes, you don't need hair) and the human reduced alimentary canal (if you got fire technology, and cook your food, you don't need so much gut for digestion).

It would have led to leaving the trees and social cooperation. That is, a bunch of small apes wielding long sharp branches as spears, and working together can drive off predators like hyaenas and leopards - possibly even lions. Thus they can leave the trees and roam the savannah where food is more abundant.

Dolphin evolution would have come from social cooperation to catch prey and to harass predators that might threaten their young. Human evolution was strongly influenced by the need to develop strong tool and weapon using ability, and indirectly by the benefits that came from simple technology.

Originally Posted by skeptic

once pre-humans became dependent on tools, the best tool users had a selective advantage, and evolution was driven towards increasing ability to use tools.

This led to upright stance, big brains, dexterous fingers, strong legs and weaker arms. The applications of tool use and simple technology led to loss of body hair (if you got clothes, you don't need hair)

I definitely like the gist of the point you made in the post above, and tend to agree with most of it... except for the bit I've quoted in my post here. In my estimation, a much more likely explanation for upright walking is simple energy efficiency. We reached a state where we needed to cover larger distances to track our prey, and traveling on two limbs upright consumes far less energy than traveling on all four... especially over long distances, such as those involved while we were tracking/following migrating herds.

Along similar lines, I find another explanation for the loss of hair to be much more compelling, and well inline with my description above about traveling long distances... and that is a hypothesis of cooling via sweat glands. We would heat up quite significantly while traveling/running long distances, and the evaporation of sweat was quite a powerful adaptation which would have been heavily selected for among pack members who were "surviving by chasing."

Like I said, though, I tend to agree with the larger gist of your idea, and just wanted to offer two possible alternative explanations for upright walking and loss of hair, but I fear we are now dangerously off-topic from intelligence in dolphins. Enjoy.

Originally Posted by marnixR

i think that what spurious was trying to say is that not all group behaviour is an indication of intelligence

You are a mindreader.

Originally Posted by skeptic

...one very major step further. They became so dependent on tool use that the faculty to use tools became a powerful driver of evolution in its own right.

Yeah, we both see how evolution can stretch a trait out until it happens to cross a threshold enabling a potent new use for that trait. Then that new use gets stretched out. Steps.

Do you suppose a dolphin uses more brain on spacial/physics thinking, or social thinking?

To iNow
Re loss of hair.
For a long time there has been a theory that human evolution of functional hairlessness has been to gain the benefits of improved cooling, as you said, and also to make parasite removel easier.

Now that is fine, as far as it goes. However, it does not answer the question of why it is that humans are the only terrestrial mammals in our size range to lose hair, and thus gain those advantages. Those advantages should drive evolution for a whole lot of mammals towards hairlessness, not just humans.

The answer to the conundrum is simple. If our pre-human ancestors had a technological alternative to hair for keeping warm when it got cold, then they could evolve functional hairlessness, gaining the advantages of superior cooling, and parasite control, without losing the advantage of thermal insulation when conditions were cold.

Bear in mind that, even on the equator, there are mornings when the temperature drops severely. Other animals, besides humans, kept their hair. My theory is that humans lost their hair only after they had an alternative for keeping warm.

Our ancestor, Homo habilis, lived more than 2 million years ago, and already had a brain size of 700 cc, twice that of a chimp. Is it too much to suggest that these guys found an alternative to hair for keeping warm? Or perhaps it was Homo erectus, 1 million years ago, who had a brain size of 1000 cc?

After all, human brain size, at 1200 cc, was enough to invent super-computers. I am only suggesting a very simple invention for our predecessors.

Hey, thanks for your post. this topic is really interesting to me. i haven't logged on in a while and im just getting to ur posts. I agree with Pong and skeptic, i think the bubble video (asides from being genuinely all around cool!) is an example of dolphins not only actively practicing/studying fluid dynamics but it looks like they have adapted what have to be the basics of advanced fish hunting into a game. A game!, this is how we as children learn and develop many things necessary for our success in later life. I think that this video is solid video documentation of the dolphins' method for passing knowledge to other generations and, as in human nature, games inspire competition which inevitably leads to innovation and higher levels of competition. or at the very least better practice.

Anyone know somebody that works with dolphins?? It would be simple enough to build a machine that produces bubble rings, maybe we should place machines that periodically "burp" bubble rings into a dolphins tanks. Hopefully it would encourage the dolphins to play with the bubbles more often???

Re bubble rings.

I am a keen scuba diver, and I have blown bubble rings myself. Admittedly, nowhere near as well as the dolphin!

However, blowing bubble rings is a game scuba divers often play when we are forced to hang off a rope under a boat undergoing decompression. Otherwise we get horribly bored.

To do it requires still water. So the diver keeps very still to avoid inducing water turbulence. It requires your mouth held in the right shape - as near to a perfect circle as possible. And it require the air to be blown out your mouth in a short sharp puff. Get it all right, and a ring of air is the result.

Maybe some experiments could be designed around divers and dolphins blowing rings. This has the advantage of behaviour dolphins readily engage in, not associated with reward. Counting?

Now that is fine, as far as it goes. However, it does not answer the question of why it is that humans are the only terrestrial mammals in our size range to lose hair, and thus gain those advantages. .

false:
compare aardvark

with natural human:


Aardvark is even smaller than a human.

SM

Ha ha!
Aardvaarks are actually very hairy, but a good visual joke.

If you want a good example of a small mammal low on hair, try the naked mole rat.

http://en.wikipedia.org/wiki/Naked_mole_rat

This animal is very atypical in that it is hairless and small. It gets away with this because it lives in small enclosed spaces, and can warm up by huddling together with its friends. However, it still does not change my statement since it is not in our size range.

It's actually quite difficult to find reliable information on the fur of the aardvark, so take the following quote with some caution, but!

They have thick skin but are sparsely furred. It seems that the fur thickness may vary geographically, with animals in southern Africa having quite thick fur on the legs, thighs and flanks, while aardvarks of rainforests are almost bald.

Interesting that you mention the naked molerat as well.

It seems diggers tend to become become 'naked' as well.

That makes you wonder if there hasn't been a bias in assuming the position of the human species.

They got naked because they were so intelligent they could make clothes.
They got naked because they went into the water.
They got naked so they could sweat more efficiently (thermal optimized hunter).

Maybe we were just diggers for a while and got naked because of that.

But who would ever think it is sexy that we used to dig for our lives?

Tom Selleck's ancestors must have evolved in a really cold climate. I hear even female Sellecks have moustaches.

Dunno, I have quite the same amount of fur as Tom. It isn't really exceptional. It's just that in the modern media most men shave themselves.

This gives the fictitious impression that humans are hairless.

Same for women. You should see their legs when they didn't have the opportunity to wax their legs.

And in case you are a young person. The amount of body hair (length that is) increases over time quite spectacularly. I had almost no body hair at the age of 20.

Originally Posted by TheBiologista

Tom Selleck's ancestors must have evolved in a really cold climate. I hear even female Sellecks have moustaches.

Talk about a bad mutation in evolutionary terms! They would never be able to reproduce. :-D

Dunno, I have quite the same amount of fur as Tom

You're a fire risk then!

Originally Posted by spuriousmonkey

And in case you are a young person. The amount of body hair (length that is) increases over time quite spectacularly. I had almost no body hair at the age of 20.

Why do I have hair where there was no hair before?

I'm 29, but I am fair haired so I don't get the gorilla suit effect. My brother, by contrast, has dark hair and looks like a walking shag pile carpet.

Originally Posted by TheBiologista

Why do I have hair where there was no hair before?

i feel that is a question that you probably should have asked around the age of 13 :wink: just kidding

just saying the dolphin ring video was definitely the cutest thing i have ever seen in my life

Humans are not actually hairless. In fact, they have more hairs per square centimetre of skin than chimps. However, chimp hairs are longer and thicker, and far more obvious.

Humans, strictly speaking, are functionally hairless. That is, the hairs we have do not carry out the old function of thermal insulation, since they are too short and too thin.

However, as with every biological characteristic, the length and thickness of those hairs vary enormously from individual to individual, and there will always be a few Tom Sellecks (or worse) with obvious foliage.

Hairs aren't only for insulation. Kinky hairs are better for cooling by sweat dispersal. Hairs can also protect against cuts and chafing. To that end, they're better long and wiry, like the aardvark's. Notice where the human body grows thick skin, it does not bother to grow such hairs.

for human hair now though, on top of our heads, if you don't keep good care of it, it will turn into dread locks. is that how hair is naturally supposed to be? i mean because if we were more primative we wouldn't care about washing it. so that would mean that there probably is an evolutionary benefit for dread locks. right?

It's a distinctive look. All species with a "sting" like porcupines and skunks benefit from making identity plain to predators. Pumas, hyenas, and those f*cking baboons learn to keep their distance. We wouldn't want to be mistaken in the bush for just any pushover hominid would we?

With our threat display topmost and omni-directional, predators will make a u-turn even when we haven't noticed them. Add a warning call - singing, as advised in bear country - so even in the thickest jungle animals know and fear man's approach.

Pong

Don't be too sure. There are plenty of predators will happily attack, kill and eat a human. Tigers. Lions. Leopards. Polar bears. Hyenas. Even the old grizzly on occasion.

That's because we've lost contact and don't condition them anymore. Moderns don't mob predators and pelt them with sticks and stones, as our wild cousins do. So how can predators learn? I'm not saying these are hard instincts - see the cougar cub gets one brush with porcupine and never repeats.

The scarecrow works better after you've thrown rocks at the crows.

I will concede we probably never mastered lions and tigers though.

i think the reason is that evolutionarily, all beings have learne to generalize, recognize common cues that tells the being how it should react. I say beings because both people and animals do this.

poison dart frogs are brightly colored to war that if you eat them, you will die- so animals learn not to touch them. then other animals will take advantage of that, and evolve so that they are brightly colored even if they are not poisonous.

some buterflies evolve to look like they are the faces of predators, so they take advantage of generalization


rules of the wild

if it is loud, it is dangerous
if it is bright, it is poisonous

there has to be more, if anyone comes up with some, add them

i believe that you are on to something. however i would be cautious to agree because large generalizations create large niches for predators to exploit thereby negating the generalization through Darwinism