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The Evolution of Life Histories, by Stephen C. Stearns. New York: Oxford University Press, 1992. 249 pp. 29.95 (paper).
The Evolution of Life Histories: Theory and Analysis, by Derek A. Roff. New York: Chapman & Hall, 1992. 535 pp. 35.00 (paper).
"Life history" is a confusing term because it refers to lots of things: the age schedule of fertility, the life span, the rate of senescence, body size and age at maturity, and the pattern of parental care. The common feature that unites these disparate phenomena is that all involve trade-offs across time. For example, an animal that delays maturation may grow larger and have correspondingly greater fertility later in life. The animal is sacrificing early fertility in return for a delayed fertility advantage. Under what circumstances will delayed maturity evolve? Elementary evolutionary theory cannot answer this question because it treats all events within a generation as simultaneous. It cannot tell us whether a unit increase in fertility at age 20 is worth more or less than one at age 30. To answer such questions, we must turn to the theory of life history evolution.
Life history evolution is of particular...