It's virtually a platitude among scientific studies that sharks have changed little over their 400 million year+ evolutionary heritage. On the one hand, sizes span from tiny varieties to leviathans like megalodon and heads can look as bizarre as a hammerhead or feature vertical-oriented jaws like helicoprion. But on the other hand, the basic shape and proportions are nearly identical and would be recognizable no matter which epoch in natural history we pull them from. The uniformity is especially striking if we consider that over similar periods of time (and yes, I'm cherry picking, but still):
- Extremely diverse species of dinosaurs evolved from proto-dinosaurs (ornithodirans)
- Extremely diverse array of mammals evolved from rodent-like creatures
An excellent quote on the subject by Andrew Lo:
The great white shark is so finely tuned to its environment that almost any change to its anatomy or behavior would make it worse off. And because of natural selection, any less well-adapted shark would be out-reproduced in the long run, or perhaps even more suddenly than we think.
These finned fellows are at the bleeding edge of the evolutionary arms race to have survived so long with so little changes. The only threat I can think of would be killer whales, which have been documented to kill great white sharks. But for my world, I just want to devise a environment-triggered explosion of shark adaptation and differentiation. 400 million years is a long time, no doubt about it, but it's not that long considering the entirety of earth's history.
That said, I'm not entirely sure it can be done because even something as extreme as a near world-ending extinction event like a giant meteor crash didn't disturb shark's evolutionary direction all that much. But maybe I'm thinking about it the wrong way. I'd imagine nature has a whole bunch of aces up her sleeves for this kind of challenge.
Purely for fun (not even that different-looking):
QuestionIs there anything in earth's **billions** of years of history that we can bring to bear to offer a scientific explanation for a huge uptick in the degree of adaptations of sharks (analogous to rodents evolving to elephants)?
Quality metric: Size and head shape are good starters, but answers that can deliver explanations for entirely different body proportions or parts would be preferred.