These animals represent only one tiny twig on one branch of the tree of life.

We can trace their histories back through time to understand how they are related.

All of the animals, including the caiman and the parrot, are members of certain lineages, represented by the lines on the diagram.

We can trace each lineage back to where they intersect.

Each of these lineages has its own unique history, but each also shares a part of its history with others.

Let's see how this works with the caiman and the parrot.

Click on each of the numbers below to illustrate parts of their histories.

1) Each has its own distinct history

2) They also share a part of their history

3) Somewhere back in time they shared a common ancestor

Using this diagram, we trace the lineages of the caiman and parrot back to a common point that represents their most recent common ancestor.

Now let's expand our explanation.