  Sol argues that innovation propensity is not a specialized adaptation
resulting from targeted selection but an instance of exaptation because
selection cannot act on situations that are only encountered once. In
exaptation, a trait that originally evolved to solve one problem is co-opted to
solve a new problem; thus the trait or traits in question must be necessary and
sufficient to solve the new problem. Sol claims that traits such as persistence
and neophilia, are necessary and sufficient for animal innovation, which is a
matter of trial and error. We suggest that this explanation does not extend to
human innovation, which involves strategy, logic, intuition, and insight, and
requires traits that evolved, not as a byproduct of some other function, but
for the purpose of coming up with adaptive responses to environmental
variability itself. We point to an agent based model that indicates the
feasibility of two such proposed traits: (1) chaining, the ability to construct
complex thoughts from simple ones, and (2) contextual focus, the ability to
shift between convergent and divergent modes of thought. We agree that there is
a sense in which innovation is exaptation--it occurs when an existing object or
behaviour is adapted to new needs or tastes--and refer to a mathematical model
of biological and cultural exaltation. We conclude that much is gained by
comparing and contrasting animal and human innovation.
