He and his sister, Kathleen Poston Wood, were born into a large Irish Catholic family who all lived within a few blocks of each other in San Francisco, CA.

Poston served on active duty in the U.S. Army as a First Lieutenant and as a Captain from 1968 to 1970, including a tour of nearly one full year in 1969–70 in South Vietnam.

The intellectual rigor of being taught by Jesuits at St Ignatius High School and the University of San Francisco has had a profound effect on his education and love of learning.

While at San Francisco State College, Poston took two sociology courses from Dr. David Dodge who encouraged him to pursue his doctoral degree at the University of Oregon.

In his first years as an assistant professor at the University of Texas in the early 1970s, Poston cites his senior colleague Dr. Harley Browning as a mentor and a tremendous help to his continued development as a researcher and working with Parker Frisbie as having broadened his demographic and ecological horizons immensely.

Poston's research interests include demography, human ecology, and the sociology of gender, with special attention to the populations of China, Taiwan, and Korea.

In his 49+ years as a faculty member at three universities, Poston chaired the doctoral committees of 65 graduate students who received their PhD degrees under his direction.