p.270
"The genetic dictionary has 64 DNA words of three letters each. Every
one of these words has a precise translation into protein language
(either a particular amino acid or a punctuation mark). The language
appears to be arbitrary in the same sense as a human language is
arbitrary (there is nothing intrinsic in the sound of the word 'house',
for instance, which suggests to the listener any attribute of a
dwelling). Given this, it is a fact of great significance that every
living thing, no matter how different from others in external appearance
it may be, 'speaks' almost exactly the same language at the level of the
genes. The genetic code is universal. I regard this as near-conclusive
proof that all organisms are descended from a single common ancestor.
The odds of the same dictionary of arbitrary 'meanings' arising twice
are almost unimaginably small. As we saw in Chapter 6, there may once
have been other organisms that used a different genetic language, but
they are no longer with us. All surviving organisms are descended from a
single ancestor from which they have inherited a nearly identical,
though arbitrary, genetic dictionary, identical in almost every one of
its 64 DNA words.
p.256
"It follows from the idea of evolution that there is one uniquely
correct branching family tree of all living things, and we can base our
taxonomy upon it. In addition to its uniqueness, this taxonomy has the
singular property that I shall call perfect nesting."
p.273
"Figure 9 This family tree is correct. There are 8200794532637891559374
other ways of classifying these 20 organisms, and all of them are
wrong."