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Tom Mazanec
2019-May-13, 08:44 PM
Suppose Cetaceans go extinct in the Sixth Dying, but a few seal and/or sea lion species survive.
Is it likely they would evolve into the ecological niche of giant oceanic mammal, or is something about whales unique?

Noclevername
2019-May-13, 08:47 PM
Depends on what the ecology does over those 50 million years. Our largest whales are on the verge of losing their niche in the present day, due to changes in ocean currents from climate change cutting off their nutrient supply and other factors.

Swift
2019-May-13, 10:00 PM
I'm fine with such questions, but I think those kinds of speculations, as well as all the books/movies about what species will be around in a million years or after humans disappear, to be kind of silly. I don't think evolution is that predictable, there are too many random factors. I think deep down they also show a bias to a deeply held human belief that there is some sort of control or plan to evolution (there is a watchmaker).

ronin
2019-May-14, 04:57 AM
I'm fine with such questions, but I think those kinds of speculations, as well as all the books/movies about what species will be around in a million years or after humans disappear, to be kind of silly. I don't think evolution is that predictable, there are too many random factors. I think deep down they also show a bias to a deeply held human belief that there is some sort of control or plan to evolution (there is a watchmaker).

It's moot anyway, once Cats develop opposable thumbs and can open their own tuna cans they'll take over the world. :)

Noclevername
2019-May-14, 09:56 AM
TBH, I'm not even sure of there will still be mammals in 50 million years. There were barely mammals 50 million years ago. We might be supplanted by something new.

Tom Mazanec
2019-May-14, 12:03 PM
TBH, I'm not even sure of there will still be mammals in 50 million years. There were barely mammals 50 million years ago. We might be supplanted by something new.
Well, mammals and birds actually arose in the Jurassic, IIRC, and those are about the last new Class of animals.
BTW, how did you italicize 'mammals'? Being able to do that on this forum would be neat.

Noclevername
2019-May-14, 12:21 PM
BTW, how did you italicize 'mammals'? Being able to do that on this forum would be neat.

At the top of the "Reply" box there's a set of letters: B for Bold, I for Italics, U for Underline. Highlight the word or phrase you want to italicize and click on I. Tags will appear around the word.

Or you can add tags manually, "I" in brackets [] before and after the words. Closing brackets need a slash "/" inside the brackets

Spacedude
2019-May-14, 01:37 PM
Those steps to B, I, U are simple, I'm still trying to figure out how to do one of these quote boxes to include the poster's name, like the above? :

Originally Posted by Tom Mazanec
BTW, how did you italicize 'mammals'? Being able to do that on this forum would be neat.

Noclevername
2019-May-14, 02:53 PM
Those steps to B, I, U are simple, I'm still trying to figure out how to do one of these quote boxes to include the poster's name, like the above? :

Originally Posted by Tom Mazanec
BTW, how did you italicize 'mammals'? Being able to do that on this forum would be neat.

Hit "Reply with quote". If you need to, copy the brackets with the poster's name and paste it over the first "quote" brackets.

...And now, back to our OP.

For something like super-seals, maybe 1 to 5 million is a more conservative estimate as to how long it could take a species to reach such an extreme of gigantism, if they happen to go in that direction.

Swift
2019-May-14, 03:40 PM
From wikipedia (https://en.m.wikipedia.org/wiki/Pinniped)

Seals range in size from the 1 m (3 ft 3 in) and 45 kg (99 lb) Baikal seal to the 5 m (16 ft) and 3,200 kg (7,100 lb) southern elephant seal, which is also the largest member of the order Carnivora.
So seals are already among the biggest carnivores. I would think the fact that they are amphibious and need to continue to be to do some activities on land (like give birth and raise their pups) would have some limitation on their size.

Roger E. Moore
2019-May-14, 03:53 PM
Convergent evolution has already produced some large whale-like undersea creatures, like the bigger mosasaurs and the extinct cetacean Basilosaurus. Dougal Dixon's After Man imagined that penguins might turn into the "vortex" in 50 million years, but who knows. If it happened before and happened now, it might happen again, if we don't destroy everything first.

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

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

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

Swift
2019-May-14, 08:14 PM
Adding to my earlier thoughts, the ideas that if whales had not evolved or went extinct, that another animal, such as pinnipeds, would evolve to fill that empty niche is not an established idea in ecology.

Wkipedia on "Vacant niche" (https://en.wikipedia.org/wiki/Vacant_niche)

The issue of what exactly defines a vacant niche, also known as empty niche, and whether they exist in ecosystems is controversial. The subject is intimately tied into a much broader debate on whether ecosystems can reach equilibrium, where they could theoretically become maximally saturated with species. Given that saturation is a measure of the number of species per resource axis per ecosystem, the question becomes: is it useful to define unused resource clusters as niche 'vacancies'?

Note particularly the last bullet point

Vacant niches could potentially have several causes.

• Radical disturbances in a habitat: For example, droughts or forest fires can destroy a flora and fauna partially or completely. However, in such cases species suitable for the habitat usually survive in the neighbourhood and colonize the vacated niches, leading to a relatively fast re-establishment of the original conditions.

• Radical and long-lasting changes in the environment: such as ice ages.

• Evolutionary contingencies: suitable species did not evolve for usually unknown reasons, or niche segregation between pre-existing species created a novel niche vacancy.
So, even if one could have an empty niche, a species might not evolve to fill it. But the article goes into some detail of the difficult in defining if there exists a particular empty niche when there is no species filling it (you don't know what you are missing, unless you watched the now missing thing disappear).

Roger E. Moore
2019-May-14, 08:29 PM
So, even if one could have an empty niche, a species might not evolve to fill it. But the article goes into some detail of the difficult in defining if there exists a particular empty niche when there is no species filling it (you don't know what you are missing, unless you watched the now missing thing disappear).

My house seemed to be full of cats when we had four. Now we have ten. In theory we could have 2,000.

I don't know what I am saying now.

Tom Mazanec
2019-May-16, 11:15 PM
Could pinnipeds evolve to reproduce exclusively at sea, like whale ancestors presumably did (and I believe sea otters have)?

publiusr
2019-May-18, 07:14 PM
One bird seems to have re-evolved itself back into life:
https://in.mashable.com/science/3368/bird-re-evolves-its-way-out-of-extinction-136000-years-later

The triceratops and the rhino are really pretty much the same animal. If there is a niche, it will be filled, all other things being equal. I think one piece on evolution from SKEPTIC talked about how we need to see not distinct species in how one "thing" turns into another "thing."

It is rather more accurate to see it all as a state of play.

Noclevername
2019-May-18, 07:18 PM
If there is a niche, it will be filled, all other things being equal.

See post #12.

Swift
2019-May-20, 06:16 PM
One bird seems to have re-evolved itself back into life:
https://in.mashable.com/science/3368/bird-re-evolves-its-way-out-of-extinction-136000-years-later
That would seem to almost be a completely separate discussion (except it might be some evidence of niche filling). But I'm more than a little uncertain if it is accurate to say this bird re-evolved itself (and yes, the press is saying that). I suspect it is more accurate to say a new flightless species of rail very similar to this extinct species has evolved. The original species went extinct 136,000 years ago, so I suspect there is no DNA to check against the new species.



The triceratops and the rhino are really pretty much the same animal.
The both have horns and are herbivorous, but without a lot more information I would be hesitant to say they fill the same niche.


If there is a niche, it will be filled, all other things being equal. I think one piece on evolution from SKEPTIC talked about how we need to see not distinct species in how one "thing" turns into another "thing."

It is rather more accurate to see it all as a state of play.

I'm not even sure what the last sentence means. But I think most people agree that a "species" is a lot more fluid than it was once defined.