INTELLIGENT DEVELOPMENT 155A classic example involves “heat shock” proteins in fruit fl ies. As their
name suggests, this is a collection of proteins that seem to off er protection
against sudden temperature changes during development. Temperature
changes might aff ect variation in traits, recruiting variable genes in the
pro cess. But the absence of such variation in most critical traits in fl ies,
through canalization, gives the impression of little under lying ge ne tic
variation. However, when transcription of heat shock proteins is chemi-
cally inhibited, huge variations in nearly every structure of the body
suddenly appear.
Th e eff ect is rather like a population of humans suddenly producing a
generation of off spring exhibiting a tenfold increase in variation in things
like height, facial appearance, numbers of legs, as well as developmental
defects. It indicates how much of the ge ne tic variation in organisms is
normally buff ered in development by regulatory interactions. Only under
extreme circumstances does the formerly hidden variation become
evident. By being correlated with trait variation, such ge ne tic variation
is now available for natu ral se lection, sometimes resulting in altered evo-
lutionary trajectories. If stability of the environment is subsequently re-
stored, then canalization of new traits may once again evolve.
From at least the early 1920s, it was suspected that evolution and
development may be intertwined, and the suspicion has grown in recent
times.^13 It is now thought that dynamical developmental pro cesses,
by innovating new responses to changed environments, can account for
evolution of new species, oft en in rapid bursts, rather than gradual pro-
gress. Th is echoes Robert Lickliter’s point that such aspects of develop-
ment “generate the phenotypic variation on which natu ral se lection can
act.”^14 Many biologists now believe that development has been a major
cause of evolutionary innovation. In reviewing the evidence, Mae- Wan
Ho concludes that, in such ways, living things become active partici-
pants in shaping their own development and future evolution.^15
IS POTENTIAL IN THE EMBRYO?Intelligent developmental systems ensure that all complex forms and
functions are created in the course of development, oft en in surprisingThis content downloaded from 139.184.14.159 on Tue, 17 Oct 2017 13:53:16 UTC