Whales evolved from land-dwelling mammals approximately 50 million years ago. These early ancestors, like Pakicetus, were four-legged, hoofed mammals that lived near water. Over time, their descendants adapted to an aquatic lifestyle, eventually evolving into the whales we know today

Early Ancestors:

The ancestors of whales, known as archaeocetes, were semi-aquatic mammals that lived near water and possessed features of both land and sea animals

Adaptation to Aquatic Life:

As these early whales spent more time in the water, their bodies adapted. Their limbs evolved into flippers, their nostrils migrated to the top of their heads (forming blowholes), and they developed a streamlined body shape for swimming

Diversification:

Over millions of years, archaeocetes diversified into two main groups: the toothed whales (Odontoceti) and the baleen whales (Mysticeti)

Modern Whales:

Today's whales represent the culmination of this evolutionary journey, with various species adapted to different marine environments and feeding strategies

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The first whales appeared 50 million years ago, well after the extinction of the dinosaurs, but well before the appearance of the first humans. Their ancestor is most likely an ancient artiodactyl, i.e. a four-legged, even-toed hoofed (ungulate) land mammal, adapted for running. Cetaceans thus have a common ancestor with modern-day artiodactyls such as the cow, the pig, the camel, the giraffe and the hippopotamus.

Mammals specialized for aquatic life

The whales that we know today are extraordinarily well adapted to life in the water. Millions of years in the sea have favoured transformations to facilitate life in this new environment. Nostrils have evolved into blowholes and are now located at the top of the head. Hind limbs have disappeared and front limbs have transformed into fins. The body has lost its fur and nearly all of its hair. It is streamlined. A horizontal, powerful propeller of a tail has attached itself to the vertebral column. These adaptations blur the relationship that exists between whales and their closest living relatives.

However, whales, like humans, are mammals. They have lungs and breath air. They are warm-blooded, meaning they maintain a constant body temperature (37°C). Their offspring develop in the mothers womb, are nourished by the placenta during pregnancy and are nursed after birth.