Chapter 1: The 50-Million-Year Evolution of the Whale

In Chapter 1, we will find out what kind of animal whales really are by tracing the history of their evolution.

Though shaped like a fish, whales are a mammal species evolved from Artiodactyla (even-toed ungulates), which includes the hippopotamus. One of the proofs that whales are a mammal is that a baby whale relies on its mother’s milk to develop. A baby whale has a uniquely shaped tongue which allows it to curl around its mother’s feeding gland, or nipple, and suckle underwater. There are other mammalian characteristics in the bones of the neck and other part of the body of a whale.

The ancestors of modern-day whales were dog-like four-legged animals which walked on land about 50 million years ago. Various whale fossils tell us of their gradual adaptation to life in water: how the nostrils moved towards the top of the head, the front legs became flippers, the hind legs shrank and vanished, the fur disappeared and the skin stiffened and formed the dorsal fin and fluke.

There are currently two groups of whales: baleen and toothed. Baleen whales filter tiny prey from seawater using the hundreds of baleen plates which grow downwards from their upper jaw. A 25-million-year-old fossil skull of a baleen whale shows signs that baleen whales gradually lost their teeth as their baleens were developing.

Toothed whales can emit an ultrasonic sound similar to that of bats, which allows them to locate each other, food and danger. This is how they can “see” their environment even in murky water or the deep sea. Unlike baleen whales which filter-feed, toothed whales swallow rather than chew their food whole, despite there being teeth on both jaws as their name suggests.

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