From the earliest days of recorded history, humans have sought to understand the workings of the human body, the origins of health and disease. For centuries, experimentation on humans themselves was forbidden. Today, stringent controls on the types of research that can be done on humans are still observed, but ethical research is permitted and supported.

Most studies done on humans have been done on nonhuman species first. Medications, surgical procedures, devices such as pacemakers--these are tried first in animal species, and only after they have been found to be safe and beneficial are they tried in humans.

Research into the processes of aging carries unique challenges. Although we have a distinct interest in understanding human aging, our already long life span makes designing experiments cumbersome and largely impractical. Ethical questions also arise when human aging research is contemplated. Can scientists ethically withhold promising treatments in order to have a control group for comparisons? Can we rely on results obtained when no control group exists?

And so scientists have turned to animal models to study aging. Exciting research is taking place in a variety of species, from yeast to our nearest animal relatives, the primates. Through such work, researchers are elaborating on their theories of how and why we age. They are beginning to develop therapeutic or treatment models that modify aging in these so-called lower life forms, in the hopes of finding similar treatments for the diseases of human aging.