Sharks Larger Size Due to Predatory Womb Behavior

As of October 5th, 2020, Kenshu Shimada and other scientists have proven that the largest sharks, the megalodons, may have been able to grow so large due to predatory behavior in the womb.

The study conducted by Shimada and his colleagues focused on the teeth left over by a set of sharks coming from a common ancestor called the lamniform sharks. This sharks are extremely diverse and include the mythological megalodon shark. The current forms of the lamniform sharks are some of the fiercest in the world. There are only 15 species of lamniform sharks, but the remaining species include the mako shark and the great white shark.

The study was focused on the comparison of the shark’s teeth and the relationship between tooth size and body size because of the shark’s peculiar anatomy. The skeleton of a shark is made from cartilage meaning the skeleton decomposes. Sharks constantly shed teeth making grabbing teeth samples much easier than skeletal samples.

The tooth is also reliable in testing for body length of a shark because the tooth crown of a shark’s tooth grows proportionally to their total body length. Initially the hypothesis as to why megalodon sharks were so much larger than other species was chalked up to their warm-blooded nature. However, Shimada believed that the explanation was not good enough.

The new explanation for the sharks’s abnormal size is a process called intrauterine cannibalism. This form of cannibalism means that the first child that hatches inside the mother eats the rest of the babies. This process allows for the child to come out of the mother fully ready to protect itself against predators. This  behavior combined with other environmental factors may allow for the megalodon to grow abnormally large. However, even intrauterine cannibalism doesn’t fully explain the size of the megalodon. It is clear to scientists that the size of a megalodon is a combination of factors.

Sources used:

Cannibalism in the womb may have helped megalodon sharks become giants

https://www.tandfonline.com/doi/full/10.1080/08912963.2020.1812598