A long time ago, the 60 foot long Megalodon roamed the oceans. Fast forward to 2.6 million years ago and they went extinct. In the story I'm writing Megalodon hasn't gone extinct surviving at least up to the late middle ages.

Now the question I want to ask is: what has to happen, or to not happen, to prevent Megalodon from going extinct, preferably without radically changing the ocean's ecology?

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    $\begingroup$ Don't fight it too much, perhaps you can avoid one event, but then someone will raise half a dozen others that would have had the same effect. Just wave your hand and say it happened. $\endgroup$
    – Separatrix
    Mar 12 '20 at 12:42
  • $\begingroup$ Any kind of animal can be extinct either from human meddling or big environmental changes. You can't stop natural changes of the planet but you can educate human beings to be conscious. If you want Megalodon back in the present, invest a significant amount of time, energy and intelligence into DNA and IVF research. IMO, these kind of animals belong to past eras wheneverything was different. $\endgroup$
    – Marino
    Mar 12 '20 at 12:46
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    $\begingroup$ Downvote: lack of research. Do you understand why megalodon went extinct? Avoiding those conditions would radically alter the marine ecosystem. $\endgroup$
    – Frostfyre
    Mar 12 '20 at 12:57
  • $\begingroup$ The Megalodon went, presumably, extinct due to radical changes in the oceans ecology, so .... your question defeats it self in a sense. $\endgroup$ Mar 12 '20 at 13:00
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    $\begingroup$ Put them on diet. They've eaten too many small whales until only bigger whales remained $\endgroup$ Mar 12 '20 at 13:00

Very simple: Change continental drift slightly so that North and South America never join completely.

Scientists aren't 100% certain why Megalodon went extinct, but the most common explanation is that Megalodon went extinct due to a lack of food supply, as the diversity of baleen whales (which was Megalodon's primary source of prey) decreased a lot towards the end of the Miocene. In particular, many of the small baleen whales that followed the current that once traveled between North and South America went extinct when the continents joined. Tropical environments become no longer suitable for baleen whales. Megalodon didn't go completely extinct at that time, but its population became few and fragile, so cooling climate and competition from smaller, more adaptable sharks eventually did the big guy in.

Of course, not closing the gap between North and South America will have huge impact on the ecosystems there, but if your story is set in the Middle Ages in Europe, it's plausible to say this won't affect Europe too much (and if this is before Columbus, people won't even know the difference). It does mean the ocean ecosystem will have a lot more small baleen whales, which are the primary prey of Megalodon.

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    $\begingroup$ If you want to be even more subtle (and preserve modern geography) make it so that the continents have joined much more recently. So Megalodons still exist but are on the decline. $\endgroup$ Mar 12 '20 at 16:03

The same was said about the Coelacanth (extinct with the dinosaurs) until scientists noticed they were fairly regularly showing up in fish markets around the Indian Ocean. Turns out they just live so deep that unless you're netting deep, you'd never know they were there.

Megalodon probably disappeared because there wasn't enough prey left for a shark that big -- but the Middle Ages were a time when sea monsters were considered more likely to be real than not, and understanding of ecology was very poor, evolution hadn't ever been considered, and the idea that the Earth might be more than a few thousand years old would be hush-hushed (or, if you shouted it loudly enough and started to convince others, might get you martyred).

A shark as big as as ship wouldn't have seemed out of place in that world view, especially to seafarers in the right oceans to have seen sperm whales (of similar size), or the still bigger blue whales. There doesn't need to be an explanation, under that time's world view, of why Megalodon is still around -- they just have a shark big enough to swallow a small rowboat whole, and that's the way the world is. There aren't many of them, at least not close to continents where people willingly sail -- but there aren't none, either.


Well, there are living fossil plants that old, e.g. https://en.wikipedia.org/wiki/Wollemia An animal could survive for as long if it lived closely together with such a tree, and never actually died out because of some external event. However trees can easily survive a few years of bad weather, a species can even reappear good as new after an ice age from a few frozen seeds. Not animals. They have to move to survive a catastrophe, and after a few moves and genetic bottlenecks, they have evolved into a new species.

So my verdict would be impossible. Sorry. ;)


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