Evolution__3rd_Edition

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Preface xxiii
The great (or at any rate, one of the great) events in evolutionary biology as I have
been writing the third edition is the way genetics is becoming a macroevolutionary,
as well as a microevolutionary, subject. Historically, there has been a good working
distinction between evolutionary research on short and long timescales a between
micro- and macroevolutionary research. The distinction was one not simply of
timescales but of research methods and even institutionalized academic disciplines.
Genetics, and experimental methods generally, were used to study evolution on the
timescale of research projects a of a few years, at most. That work was done mainly in
departments of biology. Long-term evolution, over approximately 10–1,000 million
years, was studied by comparative morphology in living and fossil life forms. That work
was done more in museums and departments of geology or earth sciences, than in
biology departments.
I see the distinction between micro- and macroevolutionary research as breaking
down, in perhaps three ways. The first is through the use of molecular phylogenetics.
A phylogeny is a family tree for a group of species, and they were classically inferred
from morphological evidence. Molecular evidence started to be used in the 1960s, but
it somehow trapped itself (I caricature a little) in about 20 years of obsessive behavior,
as a small number of case studies a particularly human evolution a were endlessly
rehashed. Molecular phylogenetics broke out into life as a whole during the 1980s, and
the result has been a huge increase in the number of species for which we know, or have
evidence concerning, their phylogenetic relations.
The research program of molecular phylogenetics may have been established for
almost an academic generation, and it is certainly flourishing, but it has still only just
begun. A recent estimate is that only about 50,000 of the 1.75 million or so described
species have been put in any kind of “minitree” a that is, a phylogenetic tree with their
close relations. Sydney Brenner has remarked that the next generation of biologists has
the prospect of finding the tree of life, something that all previous generations of post-
Darwinian biologists could only dream about. In Chapter 15, we look at how the work
is being done. The new phylogenetic knowledge is not only interesting in itself, but is
also enabling many other kinds of work that were formerly impossible. We shall see
how phylogenies are being exploited in studies of coevolution and biogeography,
among other topics.
The other two ways in which molecular genetics is being used in macroevolutionary
research are more recent. I have added chapters on evolutionary genomics (Chapter
19) and “evo-devo” (Chapter 20). The addition of these two chapters in Part 5 of the
book is a small symbol of the way macroevolution has become genetic as well as paleobiological:
in my first two editions, Part 5 was almost exclusively paleontological. The
introduction of new techniques into the study of macroevolution creates an excitement
of its own. It has also resulted in a number of controversies, where the two methods
(molecular genetic and paleontological) seem to point to conflicting conclusions.
We shall look at several of those controversies, including the nature of the Cambrian
explosion and the significance of the Cretaceous–Tertiary mass extinction.
This book is about evolution as a “pure” science, but that science has practical
applications a in social affairs, in business, in medicine. Stephen Palumbi has recently
estimated that evolutionary change induced by human action costs the US economy
about $33–50 billion a year (Palumbi 2001a). The costs come from the way microbes