View Full Version : Heredity and Heritability

Saturday, December 16th, 2006, 10:02 PM
A heritable trait is most simply an offspring's trait that resembles the parents' corresponding trait. Inheritance or heredity was a focus of systematic research before its inclusion as a key concept within evolutionary theory. An influential 18th and early 19th century theory of heredity was preformationism. This view took several forms, each maintaining that organisms were passed on from one generation to the next, miniature and yet fully formed, and development was simply the growth of the miniature organism. Subsequent accounts of heredity included the theory that organisms inherited traits that their parents had developed through response to various environmental pressures. This view was widely held during the 19th century and usually attributed to Lamarck. A different concept of heredity was crucial to Darwin's view that evolutionary change results from natural selection acting upon inherited traits under variation. Weismann's experimental refutation of the inheritance of acquired traits paved the way for the combination of Darwin and Mendel's views of the nature of heredity. The systematic study of heredity in the 20th century focused on the gene as the unit of heredity. (There is a vast amount of helpful work on the history of heredity including Fox-Keller (2002), Griesemer (1994), Morange (1998), Moss (2003), Sapp (2003), Sarkar (1998), Wade (1992), Winther (2000; 2001) and contributors to Buerton et al. (Eds.) (2000).) Two traditions now dominate the study of heredity: population genetics and molecular biology. The notion of a quantitative measure of the heritability of any given trait comes from population genetics. The idea that what is inherited is a stock of DNA, or the information contained in the DNA sequence, comes from molecular biology.

Philosophical discussions of heredity have focused on the sustainability of heritability analyses and more recently on the units of heredity. Here I introduce the concept of heritability and the problems associated with it. Next the units of heredity discussion is introduced. Here I consider alternatives to the view that DNA is the most important hereditary material. The information view of heredity is introduced and discussed and finally, several alternative or supplementary views of heredity are introduced.