Genes, Brains, and Human Potential The Science and Ideology of Intelligence

140 INTELLIGENT DEVELOPMENT

HOW IT HAPPENS: DEVELOPMENTAL INTELLIGENCE

Biological Pattern Formation

Th e question is really about how one cell type becomes a host of diff er ent
cell types performing so many diff e r e n t f u n c t i o n s. A ft er all, each cell
in the body has (nearly) exactly the same genome. Th e answer is an impor-
tant illustration of adaptive production of variation, at least at this level
of biological systems.
Indeed, the answer was partly given in the previous chapter. Th ere I
off ered a glimpse of how single cells adapt to changing environments by
internalizing external structure. Th e information in that structure is

cell lineage

self-renewing

stem cells

early

progenitor cells

neuron oligodendrocyte astrocyte

FIGURE 5.2

Cells with the same genes (stem cells) can develop many diff er ent forms according
to signals assimilated from local environments; just three of the dozens of diff er ent
nerve cells are depicted here. (Redrawn from the National Institute of Neurologi-
cal  Disorders and Stroke, http:// www. ninds. nih. gov / disorders / brain basics / ninds
neuron. htm. )

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