CISAB Speaker| Michael J. Wade

C E N T E R F O R T H E I N T E G R A T I V E S T U D Y O F A N I M A L B E H A V I O R

S P E A K E R S E R I E S

Michael J. Wade

Professor
Department of Biology
Indiana University

Levels of Selection

Keynote Address for Spring 2001 Hamilton Symposium:
Interdisciplinary Seminar in Animal Behavior | International Hamilton Symposium

ABSTRACT:
Natural selection occurs in any system whose members have the properties of replication, variation, and heredity. When the system consists of cells, the variation among cell lineages in replication and death rates, and the similarity of daughter to mother cells, gives rise to among-cell selection, which determines tissue shape. When such a process operates among cells within the germ line, it can result in gametic selection or meiotic drive, one of the strongest evolutionary forces known. When selection occurs among individuals, among groups, or among species, it is called individual selection (sometimes mass selection), group selection, or species selection, respectively. The existence of levels of selection other than the individual has been a controversial topic in evolutionary biology for several reasons. It can be difficult to establish that groups have the necessary properties of replication, variation, and heredity. Even if groups do have the requisite properties, it is still not clear that some adaptations or patterns in nature can be better explained by selection among groups than by the more familiar selection among individuals. Some have suggested that adaptations, such as sociality or sex, are the distinctive signature of group selection.

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