Estimates of a trait’s heritability can be used to predict the advance through selective breeding in agriculture and the laboratory where researchers can replicate varieties and locations. These conditions do not apply to human populations, yet considerable attention is still given to high heritability and to small effects of family members growing up together relative to differences within families. This article shows that the conventional partitioning of a trait’s variation produces components that cannot be associated reliably with average differences among (...) varieties and locations , let alone underwrite hypotheses about measurable genetic and environmental influences. (shrink)

Many psychometricians and behavioral geneticists believe that high heritability of IQ test scores within racial groups coupled with environmental hypotheses failing to account for the differences between the mean scores for groups lends plausibility to explanations of mean differences in terms of genetic factors. I show that heritability estimates and the statistical analysis of variance on which they are based have limited relevance in exposing genetic and environmental factors operating within any single group or population. I begin with agricultural investigations, (...) where replication of genetic types and control over environmental factors are possible, and highlight the difficulties of moving from AOV of observed traits to investigation of measurable genetic factors. The difficulties can only be exacerbated for human data sets, which are equivalent to a crop trial in which each variety is replicated in only one or two of the locations. (shrink)

Many psychometricians and behavioral geneticists believe that high heritability of IQ test scores within racial groups coupled with environmental hypotheses failing to account for the differences between the mean scores for groups lends plausibility to explanations of mean differences in terms of genetic factors. This two-component argument cannot be sustained when viewed in the light of the conceptual and methodological themes introduced in Taylor . These themes concern the difficulties of moving from the statistical analysis of variance of observed traits (...) to investigation of measurable genetic factors and measurable environmental factors. One such theme is that quantities estimated by an AOV of observed traits cannot be equated with measurable genetic or environmental factors involved in the development of those traits. Once this distinction is clear, the argument that environmental factors have failed to explain the differences lacks weight because it does not consider whether genetic factors have been more successful. This article exposes additional flaws in the lines of thinking associated with the two-component argument, with the distinction between passive, reactive, and active associations between genetic and environmental factors, and with the reciprocal causation models Dickens and Flynn propose in order to reconcile high estimates of heritability and large IQ test score gains between generations. Human heritability estimates are irrelevant in developing explanations of differences across groups or across generations. My critique is directed at opening up more conceptual space for deriving empirically validated models of developmental pathways whose components are heterogeneous and differ among individuals at any one time and over generations. (shrink)

In this book, Neven Sesardic defends the view that it is both possible and useful to measure the separate contributions of heredity and environment to the explanation of human psychological differences. He critically examines the view - very widely accepted by scientists, social scientists and philosophers of science - that heritability estimates have no causal implications and are devoid of any interest. In a series of clearly written chapters he introduces the reader to the problems and subjects the arguments to (...) close philosophical scrutiny. His conclusion is that anti-heritability arguments are based on conceptual confusions and misunderstandings of behavioural genetics. His book is a fresh and compelling intervention in a very contentious debate. (shrink)

Ambitiously identifying fresh issues in the study of complex systems, Peter J. Taylor, in a model of interdisciplinary exploration, makes these concerns accessible to scholars in the fields of ecology, environmental science, and science studies. Unruly Complexity explores concepts used to deal with complexity in three realms: ecology and socio-environmental change; the collective constitution of knowledge; and the interpretations of science as they influence subsequent research. For each realm Taylor shows that unruly complexity-situations that lack definite boundaries, where what goes (...) on "outside" continually restructures what is "inside," and where diverse processes come together to produce change-should not be suppressed by partitioning complexity into well-bounded systems that can be studied or managed from an outside vantage point. Using case studies from Australia, North America, and Africa, he encourages readers to be troubled by conventional boundaries-especially between science and the interpretation of science-and to reflect more self-consciously on the conceptual and practical choices researchers make. (shrink)

Despite a long history of debates about the heritability of human traits by researchers and other critical commentators, the possible heterogeneity of genetic and environmental factors that underlie patterns in observed traits has not been recognized as a significant conceptual and methodological issue. This article is structured to stimulate a wide range of readers to pursue diverse implications of underlying heterogeneity and of its absence from previous debates. Section 1, a condensed critique of previous conceptualizations and interpretations of heritability studies, (...) consists of three core propositions centered on heterogeneity and six supplementary propositions. Reference is made to agricultural evaluation trials in which a number of different genetically replicable varieties are raised in multiple replicates in one or more locations. In such analyses, the best case for illuminating genetic and environmental factors can be achieved; analyses in human genetics, in contrast, fall far short of the ideal. Section 2 identifies a wide range of questions that invite philosophical, historical, sociological, and scientific inquiry. These are organized under four headings: debate over the conceptual implications of heterogeneity; history of translation of methods from agriculture and laboratory breeding into human genetic analysis; racialized imaginaries in the analysis of differences among groups; and areas of scientific inquiry that may allow more attention to underlying heterogeneity. (shrink)