The brain on vertebrates

Some of the first vertebrates animals appear around of 500 million years ago, they may have a resembled the modern hagfish in form.

The sharks appear around 450 million years ago, the amphibians around 400 million years ago, the reptiles about 350 million years ago and the mammals around 200 millions of years ago any of this species could be described as more primitive than other one because each one has an equally long evolutionary history;  but anyway the brains of the modern hagfishes such as lampreys, sharks, reptiles and mammals, all the brains of this animals contain the same basic anatomical components.

It is very simple compared on the brains on the terms of their size, there a relationship between brain size and body size that it has been studied across a very long range of vertebrate species. It is almost a rule as the body size gets big the brain size increase also but this does not happened in a simple linear proportion,

Normally animals with small size use to have a very long brains, this size of the brain is measured as a fraction of the body size.

Soft tissue is the material that conform the brain of the vertebrates, this tissue is pink in the outside of the brain, but it is very able to a variations in color.