1920's

• Rejecting the inherently racist assumptions that served as an underpinning for Morgan's unilinear cultural evolution, Franz Boas and his students begin collecting massive amounts of ethnographic data in North America. Their disproof of race as a factor in social evolution led them to argue for archaeology as a descriptive science, leading to a generation skeptical of any theoretical frameworks, particularly evolutionary ones.
• 1922, Against all odds, Howard Carter discovers Tutankhamun's tomb, arguably the most spectacular discovery in the history of archaeology. The find provokes a media frenzy as big as any modern sensation, and engenders a wave of Egyptomania in the United States and Europe, infusing the Art Deco movement with Egyptian themes and leading to a host of Egypt themed films, including teh predecessor of the current Mummy franchise.
• 1924, Raymond Dart discovers Australopithicus in a South African quarry, demonstrating the African origins of humanity. His discovery is initially treated with skepticism and ridicule, but he is eventually vindicated.
• 1926, Woolley excavates at Ur, uncovers remains of its famous ziggerat and a whole neighborhood of ordinary houses, shops and local shrines that provide an invaluable insight into daily life 4000 years ago. He also discovers the royal tombs of the Early Dynastic Period, rivalling Tutankhamun in terms of splendour and documenting the macabre practice of human sacrifice that accompanied the burial of kings and queens of Ur.
• Tree-Ring Dating (Dendrochronology) is perfected for use in the Southwestern United States by A. E. Douglas, an astronomer. This was the first method developed for determining the chrnonological age of archaeological sites. It is still used today, but most importanly was used in conjunction with Radiocarbon dating to provide an important correction curve that greatly increased the accuracy of that method.

1930's

• Vere Gordon Childe develops the first substantial theoretical framework for archaeology by combining the economic theories of Karl Marx with the unilineal evolution theories of Tyler and Morgan. He coins the concepts of an Agricultural and Urban Revolution that started in the ancient Near East and spread throughout the world through diffusion, lead to the emergence of Western civilization. His books also helped popularize archaeology to a wide audience. Trivia: he is mentioned in Indiana Jones and the Kingdom of the Crystal Skull.
• The Midwestern Taxonomic System is proposed by W. C. McKern and colleagues as an improved method for organizing archaeological data collected within large regions. It is widely applied in the United States through the 1960's.
• Mortimer Wheeler develops the grid system for excavations, a significant improvement in systematic excavation. It was later called Wheeler-Kenyon method after improvents devleoped by Kathleen Kenyon, who worked at important sites in Israel-Palestine, most notably Jericho. Their system employing a 5 by 5 meter grid with baulks left between the squares is still widely used today in the Old World. Notable for discoveries in Pakistan outlining the Indus Valley Civilization, he also popularized archaeology in the 1950's, hosting three television shows and writing popular accounts of his excavations.

1940's

• W. W. Taylor publishes A Study of Archaeology, which criticizes archaeology for not dealing with culture and cultural development as human bio-social phenomena. It firmly links the disciplines of archaeology and anthropology.
• 1940's and 50's, Julian Steward proposes a theoretical model of cultural evolution that is multi-linear and based on ecological principles. This model is known as Cultural Ecology because of its emphasis on human-environment interaction as a causal force in explaining the development of social structures. Steward emphasizes the search for cross cultural comparisons demonstrating regularities in major developments like the the emergence of settled life and state societies. He rejects Childe and Morgan's concepts of unilinear evolution for a more complex model of multi-linear evolution, aknowledging that human societies can take many paths towards complex society.
• 1949, W. F. Libby, J. R. Arnold, and colleagues at the University of Chicago develop the technique of Radiocarbon dating, revolutionizing archaeological chronology. He demonstrated the accuracy of the technique by correctly dating an ancient Egyptian boat found next to a royal tomb. For the first time archaeologists had a tool for dating sites and artifacts from anywhere in the world back to about 50,000 years before present. In 1960, the importance of this discovery was acknowledged with a Nobel Prize in Chemistry.

1950's

• 1949-51, Grahame Clarke excavates at Starr Carr, revolutionizing the study of Mesolithic Europe. He trained a generation of influential archaeologists in his approach to interpreting ancient societies that emphasized placing cultural, social and economic reconstructions within their ancient ecological settings. He said of archaeology: "If anyone were to ask me why I have spent my life studying prehistory, I would only say that I have remained under the spell of a subject which seeks to discover how we became human beings endowed with minds and souls before we had learned to write."
• Albert Spaulding forcasts that the application of statistics, quantitative methods, and high speed digital computers will revolutionize archaeology. The wide availability of powerful personal computers today means that even the most powerful statistical analytical tools are now an invaluable tool for archaeolgists, as Spaulding envisioned.
• 1959, Mary and Louis Leaky discover Zinjanthropus at Olduvai Gorge, a noted robust Australopithecine that helps establish northeast africa as the cradle of humanity.

1960's & 70's

• Lewis Binford in the United States and David L. Clark in Great Britain begin calling for a more rigorous scientific approach to archaeology and the evaluation of archaeological data. These critiques prompt the founding of the "New Archaeology," also known as Processual Archaeology. This approach built on the legacy of scholars like Childe and Steward by emphasizing the importance of human-environment interactions in determining the evolution of human societies through an explicitly anthropological, theoretical approach. Their emphasis on a problem-oriented focus made an important contribution within a discipline still dominated by more of a particularistic, culture history approach. Binford continues to argue for a methodology grounded in the scientific method by employing a hypothetico-deductive approach.

1980's and Onwards

• 1986: Ian Hodder shakes up the archaeological world through his Post-Processual mainfesto, Reading the Past. Current approaches to interpretation in archaeology, arguing for a more humanistic approach connected to the broader Post-Modern intellectual movement. Largely a critique of Processual Archaeology, he emphasized the importance of symbolic meaning in reconstructing everyday life, a topic neglected in the "New Archaeology." Scholars like Binford saw phenomena like religion and symbolism as difficult to understand without textual evidence, which is true, but also reduced these important features of any society to the status of epiphenomena - a byproduct of and not a relevent factor in the development of human societies. Hodder rightly critiqued this view, and chose to work at the important Neolithic settlement of Çatal Hüyük in Turkey, where there is ample evidence of religious symbolism. His work there reflects the goals of his Postprocessual or Contextual approach by a combining a careful consideration of context to get at symbolic meaning, site conservation and presentation, and outreach to the public both local and international. His organization of the project also experiments with the idea of allowing every member of his archaeological team to interpret the site themselves. You too can join in the interpretive fun at his too-cool web site, which even includes comic book archaeology! http://www.smm.org/catal/