Friday, October 23, 2009

Dolphins, whales and porpoises - Mammals?

If you have never thought about evolution, take a look at dolphins, whales and porpoises. Ask yourself : Why do they look so different from other mammals?

When you see dolphins, whales and porpoises, what comes to your mind first? For me, I immediately ponder why these mammals live in water, unlike most of their counterparts who live on the land.

Why do these mammals live in water? The answer is evolution.

First, let us define what a mammal is scientifically. A mammal possesses sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain. Female mammals give birth to young and have mammary glands (milk-feeding).

Dolphins, mammals and porpoises are called cetaceans and they are classified under mammals because they need to breathe air from the surface, the bones of their fins resemble the jointed hands of mammals and the vertical movement of their spines is more similar to a running mammal than the horizontal movement of fish.

Cetaceans evolve from land-living mammals for then ten million years ago. Their ancestors through millions of years, began to live near water (like the modern hippopotamus) and through another millions of years began to evolve to adapt to aquatic life.

Here is how cetaceans probably evolved, according to fossil findings, evidence and the study of bone structure.

Earliest ancestor of the dolphins, whales and porpoises - Pakicetus

Notice the limbs have grown shorter through millions of years and the tail has evolved to a flat tail to aid in swimming
At this stage, it somehow resembles a sea lion

Limbs are almost gone at this stage as they hinder swimming. Body has become more streamlined and there is minimal hair to increase speed in water

A need to come up to breathe - The dolphin, the smartest mammal after humans

Some other mammals that have obviously evolved from land-living creatures are the sea lions, platypuses, walruses etc.

While the bat is a mammal that has undergone evolution too, to aid it in flight.

The evidence is there. It just BLOWS MY MIND to know how nature survives on its own, how species evolve to outlast, outwit each other and to survive and to thrive.

Only the fittest survives in the natural world. If you change, adapt and evolve to suit your environment, you will have the highest chance of survival.


  1. very convincing read. thank you!

  2. We understand more of space then we do of the ocean.