Just as one would expect if evolution is true. Lets compare cytochrome c sequences for various organisms. Each letter represents a different amino acid. V for example stands for valine. Cytochrome c, like any protein, is a sequence of amino acids strung together.
Similarity is determined how close the sequences are.
Spaces are have no signficance, they are added to make it easier to read the data. Now here are the cytochrome c sequences for some organisms. Now if evolution is true, than one should have some expection of the data shown above. Chimp cytochrome c should be closest to human followed by rabbit, bullfrog, and finally the two plants. That is, of course, what we see.