We know as humans that individuals vary widely in when they mature, when and how many children they have, and when they die. This lifetime pattern of growth, reproduction, and survival is known as an individual’s life history. In addition to the variation we see in life history patterns at the individual level, all species have a common life history strategy that helps define the average timing and nature of important life history events (Figure 54.10). Life history strategies are shaped by the way individuals within and among species allocate resources to growth, reproduction, and survival based on genetic and environmental factors. For example, in the case of humans today, the average age of puberty is 11 years, the average woman has one child at a time (except in the rare cases of multiple births), and the average life span is 70 years. These life history statistics are a product of the environmental and genetic constraints placed on humans in the twenty-first century. But they also belie the fact that human life history traits have changed dramatically from historical times and vary widely among populations around the world. Thus, as you will see, life history patterns not only vary within and among species but also through time.