152 INTELLIGENT DEVELOPMENTfairly defi nite endpoint, when the adult structure/function has been con-
structed. Some further maturation may take place, and some environ-
mental change can be coped with, but only that which varies within a
permanent set of rules and range of variation. Th at model of development
and function has also been prominent in much cognitive theory (see
chapter 7).
Living things that have been forced into more complex environments,
however, will continue to experience change on macro- and microscales
throughout life. One- shot developmental plasticities cannot cope with
such environments. What is required for survival in such conditions are
living structures and functions that can adapt to such changes through-
out the life of the individual.Lifelong Plasticity
In the early twentieth century, James Baldwin was the fi rst to suggest de-
velopmental plasticity as a strategy for dealing with environmental nov-
elty throughout life. Simple examples abound. Th ey include tanning in
the sun; growing protective skin calluses at points of friction; increasing
muscle bulk and strength with exercise; and, in animals, changing hair/
fur color and thickening with the seasons. General physiological fl uctua-
tions in response to rapidly changing environments have also been
described.
Lifelong plasticity seems to have emerged quite early in evolution, as
an extension to developmental plasticity. Certain plankton species really
need to be transparent for protection against fi sh predators, yet they also
need protection against UV light. Accordingly, they can reversibly de-
velop body pigmentation as and when needed. Whereas the skin color-
ation of most reptiles is fi xed at the end of development, that of the
chameleon retains a lifelong changeability. Birdsong control systems ex-
hibit seasonal plasticity in many species. Th ese include dramatic volume
changes of entire brain regions in response to photoperiod (length of day)
and its impact on circulating levels of sex ste roids.
Sometimes, lifelong plasticity is seen in spectacular body changes, as
in certain coral reef fi sh. As described by Gilbert Gottlieb, “ Th ese fi sh live
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