 We can also read the tree in  Figure 1  by starting with the groups on the right and moving leftward, tracing branches back to where they join at nodes. This direction takes us backwards in time, and allows us to read off which groups are more closely related to others by looking at recency of common ancestry. For example, lungfish are more closely related to frogs than they are to pufferfish since lungfish and frogs share a more recent common ancestor with each other than either does with the pufferfish. To see this, trace back along the branches from each group, starting on the right and moving left. You will converge on a node between the lungfish and frogs before reaching the node between either of those taxa and the pufferfish. Another way of saying this is that there is a monophyletic group (or clade) that includes lungfish and frogs that does not include pufferfish.