Since Hinton & Nowlan published their seminal paper (Hinton & Nowlan 1987), the
neglected evolutionary process of the Baldwin effect has been widely acknowledged.
Especially in the field of language evolution, the Baldwin effect (Baldwin 1896d,
Simpson 1953) has been expected to salvage the long-lasting deadlocked situation of
modern linguistics: i.e., it may shed light on the relationship between environment
and innateness in the formation of language.
However, as intense research of this evolutionary theory goes on, certain robust
difficulties have become apparent. One example is genotype-phenotype correlation.
By computer simulations, both Yamauchi (1999, 2001) and Mayley (19966) show
that for the Baldwin effect to work legitimately, correlation between genotypes and
phenotypes is the most essential underpinning. This is due to the fact that this type
of the Baldwin effect adopts as its core mechanism Waddington's (1975) "genetic
assimilation". In this mechanism, phenocopies have to be genetically closer to the
innately predisposed genotype. Unfortunately this is an overly naiive assumption
for the theory of language evolution. As a highly complex cognitive ability, the
possibility that this type of genotype-phenotype correlation exists in the domain of
linguistic ability is vanishingly small.
In this thesis, we develop a new type of mechanism, called "Baldwinian Niche
Construction (BNC), that has a rich explanatory power and can potentially over¬
come this bewildering problem of the Baldwin effect. BNC is based on the theory
of niche construction that has been developed by Odling-Smee et al. (2003). The
incorporation of the theory into the Baldwin effect was first suggested by Deacon
(1997) and briefly introduced by Godfrey-Smith (2003). However, its formulation
is yet incomplete.
In the thesis, first, we review the studies of the Baldwin effect in both biology
and the study of language evolution. Then the theory of BNC is more rigorously
developed. Linguistic communication has an intrinsic property that is fundamentally described in the theory of niche construction. This naturally leads us to the
theoretical necessity of BNC in language evolution. By creating a new linguistic
niche, learning discloses a previously hidden genetic variance on which the Baldwin
'canalizing' effect can take place. It requires no genetic modification in a given
genepool. There is even no need that genes responsible for learning occupy the
same loci as genes for the innate linguistic knowledge. These and other aspects of
BNC are presented with some results from computer simulations.