March 2005

The Darwinian Interlude
Biotechnology will do away with species. Good: cultural evolution is
better than natural selection.

By Freeman Dyson

Carl Woese published a provocative and illuminating article, "A New
Biology for a New Century," in the June 2004 issue of Microbiology and
Molecular Biology Reviews. His main theme is the obsolescence of
reductionist biology as it has been practiced for the last hundred
years, and the need for a new biology based on communities and
ecosystems rather than on genes and molecules. He also raises another
profoundly important question: when did Darwinian evolution begin? By
Darwinian evolution he means evolution as Darwin himself understood it,
based on the intense competition for survival among noninterbreeding
species. He presents evidence that Darwinian evolution did not go back
to the beginning of life. In early times, the process that he calls
"horizontal gene transfer," the sharing of genes between unrelated
species, was prevalent. It becomes more prevalent the further back you
go in time. Carl Woese is the world's greatest expert in the field of
microbial taxonomy. Whatever he writes, even in a speculative vein, is
to be taken seriously.

Woese is postulating a golden age of pre-Darwinian life, during which
horizontal gene transfer was universal and separate species did not
exist. Life was then a community of cells of various kinds, sharing
their genetic information so that clever chemical tricks and catalytic
processes invented by one creature could be inherited by all of them.
Evolution was a communal affair, the whole community advancing in
metabolic and reproductive efficiency as the genes of the most
efficient cells were shared. But then, one evil day, a cell resembling
a primitive bacterium happened to find itself one jump ahead of its
neighbors in efficiency. That cell separated itself from the community
and refused to share. Its offspring became the first species. With its
superior efficiency, it continued to prosper and to evolve separately.
Some millions of years later, another cell separated itself from the
community and became another species. And so it went on, until all life
was divided into species.

The basic biochemical machinery of life evolved rapidly during the few
hundred million years that preceded the Darwinian era and changed very
little in the following two billion years of microbial evolution.
Darwinian evolution is slow because individual species, once
established, evolve very little. Darwinian evolution requires species
to become extinct so that new species can replace them. Three
innovations helped to speed up the pace of evolution in the later
stages of the Darwinian era. The first was sex, which is a form of
horizontal gene transfer within species. The second innovation was
multicellular organization, which opened up a whole new world of form
and function. The third was brains, which opened a new world of
co