Species as Individuals in the Hierarchical Theory of Selection 695
futures, unless our basic view of scientific causality needs fundamental revision,
and the future can determine the present.
Hierarchical selection provides the most promising exit from this substantial
paradox: multiple copies cannot originate for future organismic benefit, but they
can evolve by present genie selection! (Later exaptive utilization in the generation
of organismal complexity illustrates the important historical principle that reasons
for origin must be sharply separated from current utility—see Chapter 11 for
extensive discussion. Evolution continually recycles, in different and creative
ways, many structures built for radically different initial reasons.) In 1970, Ohno
wrote with great prescience: "The creation of a new gene from a redundant copy of
an old gene is the most important role that gene duplication played in evolution."
Thus, if duplication requires genie selection in many or most cases, then the
first level of evolution's hierarchy not only operates with respectable relative
frequency, but even provides an indispensable boost for generating the sum-mum
bonum of our deepest prejudices—the complex organism, with eventual evolution
of a single strange mammalian species endowed with a unique capacity for self-
reflection, but occupying an isthmus of a middle state, a good vantage point for
looking down with thanks to duplicating genes, and up with awe to a tree of life
that could generate such an interesting and accidental little twig.
THE CELL-INDIVIDUAL I speak here not of free-living unicells (where cell and
organism represent the same unit of evolutionary individuality), but of cells that
generally house full genomes and form the environment of genes at the level
below, while also serving as parts and building blocks of multi-cellular organisms
at the level above. From our limited viewpoint as highly complex metazoans built
by intricate and integrated programs of embryo-logical development, we tend to
neglect this intermediary level of differential cellular proliferation (not just to build
bigger organs in the somatic environment, for such a process yields no
evolutionary reward in competition with other cells for representation in future
generations, but rather to gain preferential access to the germ line, and thus to
achieve evolutionary success by positive selection at the cell level). We neglect
this subject because positive selection now so rarely occurs at this level in complex
metazoans—and for a reason continually emphasized in this chapter: the
effectiveness of multi-cellular organisms in suppressing the differential
propagation of subparts as a necessary strategy for maintaining functional integrity,
the definitive property of individuality at the organismal level.
This suppression has been so effective, while the consequences of failure
remain so devastating, that human organisms have coined a word for the cell
lineage's major category of escape from this constraint, a name with power to
terrify stable human organisms beyond any other threat to integrity and
persistence—cancer. I suspect that we would learn much more about this large
class of diseases (mistakenly viewed by most of the public as a single entity) if