Fossil Friday: Pakicetus—The Original Whale

One small step for a mammal, one giant leap for cetacean-kind.

This furry little dude was a mammal belonging to the genus Pakicetus.

Nobu Tamura (http://spinops.blogspot.com) / Via commons.wikimedia.org

You wouldn’t know it by looking at it, but this critter is actually the leading candidate for the common ancestor to all whales. It is the earliest cetacean (a group that includes whales, dolphins, and porpoises).

Pakicetus was first discovered in a 48 million year old river delta in modern day Pakistan.

Bob Hynes © Smithsonian Institution / Via forces.si.edu

This extinct creature lived in the Early to middle Eocene—around 56-41 million years ago. This was a very warm time when oceans covered much of the land—plenty of reasons for some mammals to seek out new habitats and prey.

Pakicetus was primarily a terrestrial animal.

wiki: Ghedoghedo / Via commons.wikimedia.org

Its skeleton does look like that of many other fully land-based critters—especially its feet and teeth. But it probably did spend a great deal of time hunting in shallow waters, too. Pakicetus also has some pretty aquatic features as well. It has upward facing eyes, which likely made it possible for Pakicetus to be fully submerged with only its eyes above the surface, for example.

Pakicetus was a first and tiny step into the oceans.

Gabriel Barathieu / Via Flickr: barathieu

As geologic time wore on and it became more imperative to take advantage of the heavily oceanic Eocene world, evolution favored those mammals that could survive in the oceans. Whales, dolphins, and porpoises are the results of that evolutionary experimentation.

The evolution of whales was a thorn in Darwin’s side

In the first edition of Origin of Species, Darwin wrote:

"I can see no difficulty in a race of bears being rendered, by natural selection, more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale," – Charles Darwin, Origin of Species 1st Edition, 1859

He was ridiculed for the idea—something many creationist organizations capitalize on to this day—and he retracted it in later editions. But really, the only thing Darwin got wrong the kind of mammal that first explored the marine realm. The process he described was pretty spot on.