"When Whales Walked"

I just got done watching a PBS presentation of the title above.
Despite the catchy title, whales never actually walked.
But, their early evolutionary progenitors did.
Think about it. Whales are mammals.
Most of the mammals that live in the ocean are closely related to whales, such as dolphins.
Indeed, both the bone structure and DNA testing reveals this.

One can speculate that life itself may have started in water and much later some amphibians evolved and later full land dwellers evolved.
So, did an amphibian evolve back to full time water dwelling.
That would seem like an easier move than a land dweller doing so.
Indeed, that is closer to the truth with manatee. They appear to be closely
related to hippos, which aren't really amphibians, but do spend a large part of their life in water.

However, when one studies the bone structure, especially teeth, and DNA testing on all the known fossils,
it is discovered that whales are related to a mammal that lived sort of like a crocodile.
It had a large head, a belly that practicly dragged on the ground, and while it lived on land,
it foraged in the water. When one examines older fossils, there is another mammal
that was the size of a house cat, that appears to be an earlier progenitor.
That animal eventually gave rise to different branches that include hippos, and deer as well as the croc like mammal.

So, why would mammals move from the land to the ocean ?
Two evolutionary pressures, would be the escape from predators, and the availability of food.

Now here's the kicker. When looking at the teeth. These 2 progenitors are the closest related to elephants. During their evolution they produced elongated teeth, tusks. One extinct branch had 4 tusks. The tusks enabled them to move large objects, such as trees. Other than humans, elephants are the evolutionary branch, that most directly
changes the landscape. Indeed, as they created pathways through the forest,
it enabled our progenitors to come down from the trees and band together to travel
the savannahs via the elephant 'paved' paths. Thus, our progress is linked to the
success of elephants, and yet, humans are responsible for bringing that species
to the brink of extinction, by both elimination of habitat and slaughter while hunting for the tusks, that ironicly enabled us to come down from the trees.

I strongly suggest you watch the well done PBS video, which enables you to witness the fossils and listen to the paleontologists, as well as see the recreations of the long gone progenitors in addition to seeing the gorgeous animals & scenery.

However, that isn't available on Youtube.

But, the following quick 6 minute summary is;