Darwin's Dangerous Idea - Evolution and the Meaning of Life

84 UNIVERSAL ACID
CHAPTER 4: How did die historical process of evolution actually make the
Tree of Life? In order to understand the controversies about the power of
natural selection to explain the origins of all the Design, we must hrst learn
how to visualize the Tree of Life, getting clear about some easily misunderstood
features of its shape, and a few of the key moments in its history.
CHAPTER FOUR
The Tree of Life
1. How SHOULD WE VISUALIZE THE TREE OF LIFE?
Extinction has only separated groups: it has by no means made them;
for if every form which has ever lived on this earth were suddenly to
reappear, though it would be quite impossible to give definitions by
which each group could be distinguished from other groups, as all
would blend together by steps as fine as those between the finest
existing varieties, nevertheless a natural classification, or at least a
natural arrangement, would be possible.
—CHARLES DARWIN, Origin, p. 432
In the previous chapter, the idea of R-and-D work as analogous to moving
around in something I called Design Space was introduced on the fly, without
proper attention to detail or a definition of terms. In order to sketch the
big picture, I helped myself to several controversial claims, promising to
defend them later. Since the idea of Design Space is going to be put to heavy
use, I must now secure it, and, following Darwin's lead, I will once more
begin in the middle, by looking first at some actual patterns in some relatively
well-explored spaces. These will serve as guides, in the next chapter,
to a more general perspective on possible patterns, and the way in which
certain sorts of processes bring possibilities into reality.
Consider the Tree of Life, the graph that plots the time-line trajectories of
all the things that have ever lived on this planet—or, in other words, the total
fan-out of offspring. The rules for drawing the graph are simple. An
organism's time line begins when it is born and stops when it dies, and either
there are offspring lines emanating from it or there aren't. The close-up view
of an organism's offspring lines—if there are any—would vary in appearance
depending on several facts: whether the organism reproduces by fission or
budding, or giving birth to eggs or live young, and whether the