Did you ever speculate about how long you might live? Are you curious? If you’d like a preview of several of the key influences on how long we live,
try completing the questions at http://www. livingto100.com. Take notes about why you think each question is being asked. Once you’re finished, submit
your form. Take time to read about each of the topics, then read more about them in the text. Will you live to be 100? Only time will tell.

adults than their great-great-grandparents did. The tremendous increase in the number of older adults has focused renewed interest in how long you might live. Susie’s question about her own longevity exem­plifies this interest. Knowing how long we are likely to live is important not only for us but also for government agencies, service programs, the busi­ness world, and insurance companies. Why? The length of life has an enormous impact on just about every aspect of life, from decisions about govern­ment health care programs (how much money to allocate to health care programs to pay for much higher costs to care for more chronically ill people) to retirement policy (debates over the age at which people may collect maximum retirement benefits) to life insurance premiums (longer lives on average mean cheaper rates for young adults). Longer lives have forced change in all these areas and will con­tinue to do so for the next several decades.

Life expectancy can be examined from the per­spective of the basic developmental forces, because how long we live depends on complex interactions among biological, psychological, socioeconomic, and life-cycle forces. For example, some people, like Susie, have many relatives who live to very old age, whereas others have relatives who die young. Tendencies toward long lives (or short ones, for that matter) tend to run in families. As you will see, our “long-life genes” play a major role in governing how long we are likely to live.

But the world in which we live can affect how long we live, too. Environmental factors such as

disease and toxic chemicals modify our genetic heritage and shorten our lifetime, sometimes drasti­cally. By the same token, environmental factors such as access to high-quality medical care can sometimes offset genetic defects that would have caused early death, thereby increasing our longevity. In short, no single developmental force can account for the length of life. Let’s begin by exploring the concept of longevity. To get started, complete the exercise in the Discovering Development feature and see how long you might live. When you have finished, continue reading to discover the research base behind the numbers.