Richard MacNeish contributed significantly to the field of archeology in the 20th century. At an early age, Richard had an interest in Maya archeology and was encouraged by Alfred Vincent Kidder, who was a dominant archeologist at the time, to study archeology. A considerably large portion of Richard's field work focused on the origins of agricultural practices in different regions of the world. He spent a great number of years in south-central Mexico and the northern parts of Canada surveying and locating archeological sites. MacNeish also developed his own method of excavation, which is still used to this day.
Richard's field work in northern Tamaulipas and the Tehuacan Valley of Mexico were some of his more famous excavations, and both lead to great discoveries in prehistoric agricultural practices. The remains of corncobs found at the Tamaulipas site, placed maize agriculture back to 2500 B.C. Then his discovery of even older maize, squash, and beans at the Tehuacan site pushed agricultural practices back to around 7000 B.P.
Previous methods of excavation that Richard was familiar with, such as the 6" levels, and the Chicago methods, were not suitable for the conditions of the caves he was excavating. The La Perra method of excavation was developed by MacNeish in an effort to better excavate the caves. This method involves dividing a floor into a grid of squares and excavating in a pattern of alternating squares. His method made it easier to follow a specific living floor with a trowel, from square to square. The La Perra method is still being used in the Mexican regions where Richard had developed it.
References:
http://books.nap.edu/readingroom/books/biomems/rmacneish.html, Kent V. Flannery and Joyce Marcus
Written by Marcy L. Voelker, 2007