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As we know, the Earth had one super continent at one point in the history of our planet, which eventually broke apart to become what we have today.

Assuming we're talking about a planet near identical to Earth (size, density, distance from sun, similar atmosphere, similar geological processes, etc.), would it be possible for two super continents to have arisen early on (before life progressed into multi-cellular forms), and then stayed separate for 3-4 billion years? Is there some geological process or something else that would prevent this from happening, at least once in the galaxy?

Edits for clarification

I may have not been quite clear about my 'requirements', so a few clarifications.

  1. When I said 'Pangea' I used it as the name we typically give to the super continent that once existed.

  2. I understand that two such continents having existed at some point is entirely possible. My question is more along the lines of 'would it possible for not only those two to have existed at some point, but also to continue to exist for a long period of time such as 3-4 billion years without ever breaking apart or ever coming into contact with each other'.

Edit 2

The reason for the question is, I want to have two intelligent creatures evolve on the two continents separately, and not come into contact with each other until they've evolved into intelligent and sea-faring animals.

Sach
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    I don't think you would get evolution to have 2 separate branches of multi-cellular life. Multi cellular life, and life up through invertebrates can develop completely in the ocean before colonizing land. Birds can carry life between continents, and even trees can colonize across oceans (coconut palm) – Nate White Dec 04 '19 at 21:09
  • OK, I'm still fine with that. Suppose the two continents formed shortly after multi-cellular life. Then I can have distinct multi-cellular life forms evolve independently on each continent till they both produced intelligent creatures. – Sach Dec 04 '19 at 21:14
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    Also, you run into a timing issue. The time it took on Earth to go from Language to moonlanding is /tiny/ on the Geologic Timescale. Without something deliberately holding things in synch, one is going to develop intelligent creatures first, and they'll flash across the planet in a geologic instant. – notovny Dec 04 '19 at 21:15
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    @notovny Even with humans, who are biologically the same species. the difference in technology present in first contact gave one side of the contact a huge technological advantage. These people diverged only on the scale of tens of thousands of years, around the last ice age. – Nate White Dec 04 '19 at 21:21
  • Both of you bring up a good point. Maybe I can circumvent that problem by holding the dinosaur-like-creature phase long enough (maybe Oxygen concentration never fell, and giants roamed the world for much longer), and then something changed suddenly changing both continents and conditions were right in both for intelligent life. I understand that still leaves a lot of room for chance, so thanks, I'll think about this problem too. – Sach Dec 04 '19 at 22:37
  • You might note that we actually have two "supercontinents" on our present-day Earth: Asia+Africa+ Europe and the Americas. Then there are a few extra bits like Australia and Antarctica drifting around... – jamesqf Dec 05 '19 at 05:18

4 Answers4

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Formation of super continents and their subsequent breakup is cyclical in nature.

Supercontinent Cycle

On geological time scales it would be reasonable to assume that there was a period in which there were only 2 major landmasses present on the planet.

Your timescale of 3-4 billion years is off by an order of magnitude of the Earth's, but it would be plausible that continents on other planets could move more slowly. Your planet must be much older than Earth, who's age is estimated to be about 4.5 billion years old.

Nate White
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  • Please see the edits I've added. Follow up question: why must my planet be much older than Earth? Can't it be around 4-5 billion years as well, but continents move slowly? – Sach Dec 04 '19 at 20:57
  • I don't see why not. Your planet at 4-5 billion years would just be in it's first cycle. – Nate White Dec 04 '19 at 21:00
  • Thanks for the wp link! I always found this Pangea story a bit dodgy, esp. since it is not exactly a new theory. Makes a lot more sense now. – Karl Dec 04 '19 at 21:09
  • @NateWhite OK that makes sense. So I suppose my two continents can have existed at least once. – Sach Dec 04 '19 at 21:14
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We're pretty sure it's happened right here on a earth, a few times. Pangea didn't break up straight into seven continents, it was two big bits for a while both before it formed and after it broke up, and Pangea wasn't the first time all the continents had joined together either.

So, not only is there no process that prevents it from happening, it's pretty much guaranteed to happen at least once in the lifetime of any earthlike planet.

Morris The Cat
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On Earth, continental drift is caused by volcanic activity; so, are oceans. So without a lot more knowledge of what other worlds are actually like to maybe contridict that, a little bit of simple reasoning tells us that a planet with oceans should have significant continental drift over that time scale which makes 3-4 billion years of continental separation seem very unlikely. Furthermore, even with separate continents, you'll still probably have a enough major ice ages that would allow continental crossing via ice bridges many many times during that period.

That said, nature has your back on this one. As it turns out, it does not take super long continental separation to achieve what you are looking for. Thanks to a thing called convergent evolution, it is perfectly possible for two completely different species in different parts of the world to evolve the same characteristics given the same environmental niche and pressures. Considering how long it took humans to go from tree-swingers to computer engineers, your world only needs separate continents for about 1-2 million years to have smart lizards evolve on one land mass and smart mammals to evolve on the other without either competing for their niche until one learns to cross the Ocean.

The only thing you might need to adjust from Earth like is to make sure there are no major super volcanoes or asteroid impacts going off during that time period which might cause an ice age to bridge the gap.

Alternatively, without writing, civilizations don't exactly have the best memories of things that happened more than a few hundred years ago. It could be that your species did cross during an ice age, but they each successfully drove the other to extinction on their native continents after the ice age ended, then forgot about it.

Nosajimiki
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  • Regarding the first part, I guess it makes sense that continents will merge and/or ice sheets will eventually link them. I will dig deep into it to see if there are conditions under which the drift is slowed down. – Sach Dec 04 '19 at 22:25
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    Re. the second part, I did think about it myself, and I'm conflicted. Even consider the common ancestor of us and chimps/bonobos, that's still only 7 million-ish years, so what you say stands in that regard. But then also, if all it takes is separation for that long, then another intelligent species could have arisen in another continent, for example why didn't marsupials evolve at least one human-level intelligent species in Australia? Or any other continent other than Africa? My guess is that conditions need to be just right for intelligent life to evolve, and it's such a rare occurrence... – Sach Dec 04 '19 at 22:29
  • ... that it can only happen once in every 3-4 billion years. That's why, despite complex multi-cellular life existing on earth for close to a billion years, and more than 500 million years since the Cambrian explosion, still only one intelligent species arose. This is why I wanted to separate the continents for 3-4 billion years, so essentially we have two planets with each having that many years to develop it's own intelligent life. – Sach Dec 04 '19 at 22:31
  • Separate "worlds" should actually make simultaneous evolution of intelligent life less likely. One continent could easily fall 50 million years behind the other in terms of evolution. Instead consider the Hyena. It looks like a dog, it acts like a dog, but it's actually a rodent of unusual size that filled the niche that canines filled in other parts of the world. – Nosajimiki Dec 04 '19 at 23:01
  • I admit that timing problem is hard one to solve. This is a work in progress so I'm trying to find reasonable solutions to all these challenges. I'm not sure how Hyenas example fit in though; wouldn't it be arguing my case, that given similar niches different life forms can evolve into doing the same thing. If I can find a way to have isolated continents, but similar conditions, then there is perhaps a remote chance of two different species filling up the same 'job'. – Sach Dec 04 '19 at 23:06
  • Hyenas are an example of convergent evolution without complete continental separation. The Eurasian wolf could have come to Africa to compete for the niche or vise versa, but did not. It only took a slight climate variation for to distinct ancestries to come to the same conclusion. – Nosajimiki Dec 05 '19 at 01:09
  • Also, there is no real evidence that primates are the only source of higher intelligence on Earth. Beavers build homes and raccoons are practically caveman level tool users http://wildliferemovalusa.com/raccoontool.html. If man never crossed the Bering Strait and took on the niche of civilized creature in the Americas, either one of these creatures could have easily evolved to fill that role given enough time. For all we know, they actually did, but there more intelligent ancestors were wiped out by humans (because that's what we do to other intelligent life forms.) – Nosajimiki Dec 05 '19 at 01:19
  • https://worldbuilding.stackexchange.com/questions/146557/best-species-to-breed-to-intelligence/146649#146649 , https://worldbuilding.stackexchange.com/questions/157390/if-mammals-with-paws-were-to-evolve-to-have-human-hands-or-fingers-what-would-th/157434#157434 Here are some other interesting WB.SE questions that are not exactly duplicates, but you may draw inspiration from. – Nosajimiki Dec 05 '19 at 01:30
  • @Nosajimiki Hyena are not rodents, they are Carnivora, they are no more closely related to rodents than cats, dogs, or bears. They are actually closely related to cats. – John Dec 05 '19 at 04:38
  • I stand corrected, apparently they are an offshoot from the rodent like Mongoose family which apparently are not actually rodents. Seems the whole darn lot of them just can't stay out of other species' niches. – Nosajimiki Dec 05 '19 at 15:09
  • Thanks for the links, I will check them out. Regarding other intelligent animals, of course there are many others who possess many cognitive abilities, and have rudimentary forms of societies, tool use etc. But I used 'intelligence' in a very narrow sense simply to refer to intelligence at human level. – Sach Dec 05 '19 at 18:19
  • @Sach You should remember that on earthonly one species i sknown to have developed advanced technology and civilization, but there are many species, perhaps as many as 80 or 100 species of mammals ( leaving non mammals out of consideration) who might possibly have intelligence ranges that overlap considerably with that of humans, and thus might possibly be intelligent beings and people. The many cetacean specie are not blessed with appendages for manipulation, but sometimes use tools of a sort, while the primate and proboscidean species are known for their tool use. – M. A. Golding Dec 05 '19 at 19:51
  • @M.A.Golding, I don't doubt that. Personally, I think two things likely separate our 'intelligence' from all other life on Earth; a) we are likely the only species that intellectually understand that we are going to die someday, and b) we are the only species who've progressed to a level where we've almost halted the evolution by natural selection. Sure, we still are subject to it when it comes to deceases, how we resist bacteria, etc, but otherwise, no longer the fittest (as in most suited to the environment) get to mate while others die out. Some of the poorest nations in the world are... – Sach Dec 05 '19 at 19:59
  • ... also the most populous in the world. We take care of the sick, disabled, disadvantaged, on a level different to all the other animals, and so we've essentially halted natures ability to dictate our evolution. That is kind of my definition of 'human intelligence'. – Sach Dec 05 '19 at 20:00
  • Altruism is not uniquely human, vampire bats for example care for their sick & wounded and even feed each other when one is just less lucky on the hunt. Mortality awareness is a bit harder to prove, but it is a concept that most 3 year olds can grasp. Since many animals have at greater than or equal to 3 yr old intelligence, it's pretty likely that many animals understand it, they just don't have our language skills to tell us that they get it. – Nosajimiki Dec 05 '19 at 22:13
  • The only trait I've ever heard argued that humans have that other animals don't is the ability to originate abstract ideas. Other animals can tell eachother what they need or what has to happen, how they feel, details about the environment, etc, but humans are able to come up with things that have totally no basis in our current reality, communicate about it, then work together to make it reality. Add this one thing to any of 20+ other species, and you'd get an intelligent civilization in pretty short order.. – Nosajimiki Dec 05 '19 at 22:19
  • Children learn about mortality, they don't come to an understanding of it innately. That understanding comes from adults, I believe. Sure, altruism is not unique, but we're the ones who've 'progressed' it to a point where we are able to slow down if not completely halt evolution by natural selection. – Sach Dec 05 '19 at 23:33
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First thing first, Pangea means "all the earth", because it encompassed the whole of the emerged land back in those times.

So, from a logic point of view there can be no two Pangea.

From a geological point of view, if you look at the appearance of the present emerged lands, you might argue that we have less than 5 continents: Asia, Europe and Africa are a single continuous bunch of dryland, so it is entirely possible that only two continents existed or will exist at a given time.

L.Dutch
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  • Thank you. I may not have asked the question very clearly, so added a couple of clarifications. – Sach Dec 04 '19 at 20:55
  • North and South America were also contiguous land masses until we dug a canal between between them, and the continental shelf is contiguous in parts between Asia and Australia; so, it might even be more accurate to say we have 4 or even 3 truly separate continents depending on how you look at it. – Nosajimiki Dec 04 '19 at 22:24