Evolution and Learning: The Baldwin Effect Reconsidered. Bruce H. Weber and David J. Depew (Eds.). (2003, MIT Press.) $50 (hardcover), $25 (paper), 351 pages

Evolution and Learning: The Baldwin Effect Reconsidered. Bruce H. Weber and David J. Depew (Eds.). (2003, MIT Press.) $50 (hardcover), $25 (paper), 351 pages. ALife researchers have typically interpreted the Baldwin effect (BE) [2, 3] as a two-step evolution of the genetic acquisition of a learned trait without the Lamarckian mechanism: Individuals that have successfully adapted their own trait to the environment through their lifetime learning processes occupy the population (first step), and then the evolutionary path finds the innate trait that can replace the learned trait (second step) because of the cost of learning [17]. I think that this definition stemmed in part from the introduction of Hinton and Nowlan’s pioneering work [6] on the BE by Maynard-Smith in Nature [8]. However, what we first learn from this book is that the BE has been redefined several times and diversely interpreted in its more than 100-year history. This book is a collection of essays on this effect and related concepts, written by participants in an interdisciplinary conference on the emergence of mind and by several invited authors. It includes the history of the BE, its significance in language evolution or developmental biology, and its relationship to the evolution of consciousness or mind as an ultimate form of phenotypic plasticity. Recently, the BE and the role of phenotypic plasticity in evolution have been drawing much attention in evolutionary developmental biology; many experimental results on this effect have been reported [4, 13, 20]. Here, I summarize the topics in each chapter and then make several comments on what needs to be added, together with implications for further research on the BE in the ALife field. David J. Depew, one of the editors of this book, reviewed various versions of the BE defined by Baldwin himself, by the framers of the modern synthesis, and by the contemporary boosters of the BE such as Dennett and Deacon (Chapter 1). For example, according to Depew, natural selection is an indiscriminate force (rather than a creative force) that kills individuals before their reproduction (thus, adaptive learning keeps the individuals alive and determines evolution by securing genetic variations) in Baldwin’s original scenario of ‘‘organic selection’’ [2, 3]. On the other hand, the BE is merely a special case of Waddington’s genetic assimilation [18] for G. G. Simpson [14], who named the term ‘‘the Baldwin effect’’; however, he was skeptical about its significance. Depew states that, if the history of the BE is any guide, we should be cautious about dismissing these hypotheses just because they do not fit with existing interpretive schemes. Although Stephen M. Downes and Peter Godfrey-Smith are skeptical about the BE, they discuss the differences between these versions from several viewpoints. Downes classifies them by focusing on what kind of traits are considered and what kind of outcomes will be brought about as a result of the BE (Chapter 2). Godfrey-Smith compares the significance of several mechanisms that enable the ontogenetic adaptation (first step) to affect the acquisition of the innate trait (second step) among these versions (Chapter 3). He points out that the existence of similarity relations between genotypes can facilitate the genetic acquisition of the learned trait, but the niche construction induced by the ontogenetic adaptation is a more significant mechanism for the evolution of a novel trait that differs from the one previously acquired through the learning process. One of the controversial issues relating to the BE is language evolution, which includes both the cultural evolution of language and the evolution of language ability. Daniel Dennett and Terrence W. Deacon regard the BE or Baldwinian evolution as a key concept of language evolution; however, their scenarios are different. According to Dennett, the BE is essential to explain the genetic acquisition of a complex trait such as the innate ability for language acquisition, which is impossible