Hippos are the first cousins of whales!

In the fascinating world of evolutionary biology, the connections between seemingly unrelated creatures often astound scientists and laymen alike. One such intriguing revelation is that the closest living relatives to whales are not sharks or fish, as one might assume, but rather the humble hippopotamus. Stunned? Both hippos and whales share a common ancestor, a group of quadrupedal mammals which thrived globally approximately 40 million years ago before becoming extinct during the ice ages. This discovery has reshaped the scientific understanding of these majestic marine mammals and the complex tapestry of life on Earth.

Remarkably, the tale of whales and hippos, with their shared ancestry buried deep in the annals of time, this is one chapter in the ongoing saga of life on Earth, a story that continues to inspire wonder and ignite our passion for exploration and discovery.

Let’s look at how.

The Evidence: Genetic Clues

In the late 1700s, scientists initially observed certain similarities in the reproductive organs of whales and hippos, but these resemblances were largely dismissed as mere coincidences. Then it wasn’t until the 1980s that a pivotal discovery came to light when the remains of Pakicetus (An extinct genus of ancient cetacean mammals situated in the river delta region of Pakistan) were unearthed. These remains contained bone structures that offered crucial insights into the evolutionary connections between whales (Cetacea) and even-toed hoofed mammals (Artiodactyla), a group that includes animals like camels, pigs, and giraffes.

Pakicetus also had ear bone features for underwater hearing common to both whales and even-toed mammals. Its ankle bone had a unique double-pulley structure, seen in even-toed mammals but not odd-toed ones. These findings supported the evolutionary link between whales and certain terrestrial mammals, altering scientists’ understanding of their shared ancestry.

Boisserie’s Revelation: A Common Water-Loving Ancestor

In a study published in the Proceedings of the National Academy of Sciences, Jean-Renaud Boisserie (a scientist specialising in the Evolution of Large Mammals) put forth a groundbreaking theory that resolves this long standing conundrum. He along with his team proposed that whales and hippos indeed share a common ancestor, one that lived between 50 and 60 million years ago. This water-loving ancestor evolved and eventually diverged into two distinct lineages: the early cetaceans, which fully embraced aquatic life, and a diverse group of four-legged creatures known as anthracotheres.

Recent advances in scientific research have added exciting chapters to this captivating detective tale. A DNA study investigating the connection between whales and even-toed hoofed mammals has confirmed that whales indeed possess similar gene sequences to those found in hippos.

The Surprising Implications

Another article in the American Museum of Natural History dated April 1, 2021, states that both whales and hippos exhibit unusual traits uncommon among most mammals. These include having smooth, nearly hairless skin devoid of sebaceous glands, which typically produce sebum to lubricate the skin and hair in terrestrial mammals. But despite these similarities, whales and hippos evolved in their skin independently.

In the ever-evolving narrative of life on Earth this disclosure stands as a testament to the marvels of the natural world. As one continues to explore and uncover the secrets of evolution, it is totally impossible to predict the hidden connections that nature might still hold for all.