Whale Shark Evolution by Lindsey Hodkinson

450 million years ago

hodkinsonla26 — 2024-06-10 18:11:46 UTC

the first evidence of sharks was in the form of not a shark, but a toothless large fish called a Chimaera. It is predicted that the Chimaera did not evolve into sharks, but did cross paths with them.

380 million years ago

hodkinsonla26 — 2024-06-10 18:15:30 UTC

The first recognizable shark. Known as the Antarctilamna. Around this time period the Cladoselache showed up, another eel like shark figure that set the stage for the evolution of sharks.

The Carboniferous Period

hodkinsonla26 — 2024-06-10 18:20:39 UTC

The Carboniferous Period, also known as the golden age of sharks was a massive population boom in the species of sharks. The reasoning behind this was that 75% of species on Earth had been wiped out. This massive extinction causes sharks to be able to control the oceans and expand their species.

Early Jurassic Period

hodkinsonla26 — 2024-06-10 18:27:37 UTC

After another large population decrease, sharks were able to become more niche and only the strongest sharks survived the extinction events. Those sharks turned out to have long, durable jaws that was derived from the Hexanchiformes, or sixgill sharks during the early Jurassic period. Now sharks can hunt down prey, and move swiftl;y through dark waters. The Hexanchiformes sharks are an example of descent with modification as the whale sharks descended from them.

End-Cretaceous Period

hodkinsonla26 — 2024-06-10 18:38:04 UTC

The End-Cretaceous time period was the sharks FIFTH mass extinction event. This was not an event that sharks could just squeeze by. Only the smaller, more diverse shark species were able to live. The large species, such as the infamous megalodon, were most likely wiped out by the asteroids millions of years ago. Several factors worked against whale sharks, as they struggled for existence. From habitat destruction caused by oil and gas spills, pollution and climate change, it was a constant competition among members for necessities in life.

In 5 million years...

hodkinsonla26 — 2024-06-11 13:06:37 UTC

One of the prominent factors that sharks have had in their evolutionary history is their ability to thrive after a mass extinction. It seems that sharks become just a little bit better after 70-90% of the population is wiped out. This would suggest that if the ice age occurred and humans were wiped out, then the population of whale sharks would massively increase. Not only this, but they would start being pushed towards developing more predator-like behaviors, since the survival of sharks during mass extinction is largely attributed to their more slender species. But also because of the lack of humans and water, they will start to develop more diverse features so that they will be able to survive after major events like this. So, in 5 million years, the whale shark species will be bred to develop blubber in order to resist the cold of the ice age. They will start to develop real teeth, which scientists consider are their vestigial organs, as well as their homologous structure. This will allow them to be able to adapt to limited fish supply, and start to reduce in size due to selective breeding.

In 100 million years...

hodkinsonla26 — 2024-06-11 13:13:57 UTC

Shark whales will now be a few feet shorter, with a layer of blubber, and blind eyes. The reason for this is that as the temperature of the earth and waters increased, whale sharks started to go deeper into the ocean in order to find relief from the heat and their blubber layer. The new warm environment has caused them to struggle for existence as well. Since oceans are thriving again, there is more competition to dominate the oceans, forcing the whale shark to become reclusive, and solitary creature who can eat mostly anything with their semi sharp, semi grill teeth. They have blind eyes because in the deep oceans, their eyes have no reason to work. Their fitness will decrease, which will cause a decrease in the population as well. Adaptation will occur as sharks will have more features such as unique checkerboard pigmentation because of adaptive radiation in 100 million years. There will be more of a natural variation amongst sharks.

In 200 million years...

hodkinsonla26 — 2024-06-11 13:50:21 UTC

The oceans will now have large warm storms and freezing temperatures at night, while hot during the day. Because of this issue, whale sharks will have to develop teeth to battle the violent chaos of the oceans and the limited food from the storms. The whale sharks will have to adapt to the extreme heat changes by burrowing themselves in dark caves during the day, and swimming around at night to increase body temperature. The appearance of whale sharks is now slender, with sharp teeth, blubber, and larger noses so they can detect creatures in the deep sea without their eyes.