> It is believed that modern-day whales evolved from land-based animals about 55 million years ago. These land-based mammals are believed to be hoofed mammals, sharing a common ancestry with even-toed ungulates such as the cow and the deer.
> Evolution of Whales Whales started their journey as all other organisms have, as single-celled bacteria.
An evolutionary picture of the whales can be broken down as follows:
- 3.8 billion years ago: The first single-celled organisms appeared (Bacteria)
- 3 billion years ago: Viruses (also single-celled organisms) became present
- 2 billion years ago: Eukaryotic cells are present. These are cells that contain organelles, or tiny organ-like structures
- 1.5 billion years ago: Eukaryotic cells evolved three ways. These cells evolved into the ancestors of plants, animals, and fungi
- 900 million years ago: The first multicellular structures became present
- 800 million years ago: The animal strain of organisms undergoes its first split and continues into basic marine organisms such as sponges
- 540 million years ago: The first chordates or animals with backbones are present
- 530 million years ago: The first true vertebrate or boned organism is present
- 500 million years ago: Animals first started exploring the land
- 417 million years ago: Lungfish became present. Lungfish are the first organisms to breathe both on land and in the water with both lungs and gills
- 397 million years ago: The first tetrapods or four-legged species are present
- 340 million years ago: Amphibians branch off from the other tetrapods
- 310 million years ago: The remaining tetrapods split into what will be reptiles, birds and dinosaurs, and mammals
- 200 million years ago: A mass extinction occurred and warm-blooded proto-mammals developed
- 140 million years ago: Placental mammals also known as eutherians are present
- 105-85 million years ago: The placental mammals split into four major groups, including laurasiatheres, which will contain the whale species.
- 65 million years ago: The greatest extinction event so far wipes out the dinosaurs providing more potential for mammals to colonize the planet
- 50 million years ago: Artiodactyls pakicitus, a mammal, resembling a wolf and tapir mix with cloven hooves begins evolving into what we know as whales
- 47 million years ago: Early forms of whales live in shallow seas, returning to land to mate and give birth
- 35-45 million years ago: The first fully aquatic whale is present (Basilosaurus)
Modern-day whales are believed to have moved into the oceans around the Tethys Sea, now the Mediterranean Sea and Asia.