His fieldwork revolutionized the understanding of the development of agriculture in the New World and the prehistory of several regions of Canada, the United States and Central and South America.
His interest in archaeology started at a young age, sparked by a hastily created report on the Maya for an art history class when he was twelve.
[2] Of this time, MacNeish writes: "My energy was boundless: I dug, I hiked, I climbed cliffs, I learned, I went to dances, I mixed cement by hand, I caught rattlesnakes, I packed mules.
[3] He continued to be influenced by Dr. Kidder, and refined his field archaeology methods under George Brainerd, eventually forming his personal excavation technique La Perre.
[4] At the University of Chicago, he participated in field schools that exposed him to the methods and theories of James A. Ford, William Haag, Jesse D. Jennings, John Cotter, Glen Black, Tom Lewis, and Madeline Kneberg.
This achievement spurred his lifelong interest in the origins of agriculture and society that would take him throughout Central and South America, eventually to China and, nearly, to Turkey.
[6] After a long, varied and influential career, Richard MacNeish at age 83 died on January 16, 2001, in a car accident while touring Pre-Columbian Maya sites in Belize.
[8] His discovery in these caves of very early maize domestication evidence also brought home to him the importance of interdisciplinary studies as he struggled to get dating and identification information on his samples.
This policy was very well demonstrated in his excavations in the Tehuacan Valley and Ayacucho, Peru which resulted in multi-volume publications which analyzed the sites "utilizing the skills of all appropriate scientific fields".
With this he began a system of spending his summers surveying and excavating in Northern and Western Canada and his winters searching for evidence of the origins of agriculture across Central America.
[12] Realizing that a random search for sites over these huge swathes of territory would be difficult and inefficient, he pioneered a five-step process that was based on making and then testing hypotheses about ancient environments and human behavior in them.
These steps were: Using this process, he discovered hundreds of new sites and gained a reputation for "lucky" finds, while actually advancing the scientific foundation of archaeology.
He was a processual archaeologist who championed the necessity of experimental archaeology[23] and hypothesis testing[24] in the exploration of human cultural ecology.
In his autobiographical discussion of American archaeology (1978), MacNeish writes, "We are still fumbling along, perfecting techniques as well as improving methodology, and our field – as well as I – have a long way to go".
[26] MacNeish was constantly calling for others to question his conclusions and improve his methods to further advance the science of archeology and its ability to speak to society's needs.