Seasonality, in the archaeological sense of the word, refers to when, what season, a particular event occurs. That doesn't sound too important today, does it? Modern people notice when the weather changes throughout the year: we might have to shovel the snow off the driveway or pull out our summer clothing. But we--at least those of us in the so-called first world--aren't as a rule intimately involved in tracking and relying on food availability, insulated housing or making or repairing warm clothing. We might see a specific type of food disappear from our store shelves, or, more likely, a steeper price for the same food depending on the time of year, but if we notice it's not a serious loss.
Modern technology and global trade networks have softened the impact of the winter and summer seasons for those people on earth who have access to that. But that was not the case up until pretty recently: for pre-modern peoples, seasonality affected availability to crucial resources, and if you didn't pay attention, you didn't survive long.
Dealing with Seasonality
In temperate or colder climates, some--maybe most--natural and cultural events are tied to the natural changes that occur from season to season. Some cultural groups in the past responded to the oncoming winter season by constructing storage facilities for safely storing summer crops, others by building different types of houses, still others by temporarily relocating to warmer climates.
Religious ceremonies associated with the movements of the sun, moon and stars were scheduled for different seasons: soltices and equinoxes were celebrated with specific rites at specific seasons of the year. In a fairly broad but nonetheless meaningful way, calendar systems and astronomical observatories were created to respond to the demands of seasonality: the sooner you could recognize when the local weather will change, the better you could plan for it.
Much more than today, diets changed throughout the year: seasons determined what kinds of foods were available. If you were a hunter-gatherer, you needed to know when a particular berry was available, when the deer were likely to migrate through your area and how far they were likely to go. Farmers knew that agricultural crops ripen at different times of the year: if you planted a variety of crops, some of which ripened in spring, some in summer, and some in fall, you would have reliable resources to get you through the year. Pastoralists needed to recognize when different animals gestated at different times of the year, or when they produced their wooliest coats, or when the herd needed to be thinned.
Tracking Seasonality in Archaeology
Archaeologists use the clues left in artifacts and human remains to identify the effects of seasonality on human cultures. For example, an archaeological midden (trash heap) might contain animal bones and plant seeds: determining in what season those animals were killed or those plants harvested allows us to get closer to human behaviors than simply "the people ate thus and so".
There are a number of strategies which have been used by archaeologists to identify seasonality, most of which rely on seasonal changes recorded as growth rings. Many if not most living things record seasonal changes the way tree rings do. Animal teeth--human teeth too--record recognizable seasonal sequences; individual animals born in the same period of the year have the same pattern of growth rings. Many other organisms such as fish and shellfish also record seasonal growth rings.
Technological advances in identifying seasonality have included stable isotope analysis and ancient DNA changes in animals and plants: stable isotope balances in teeth and bones change with dietary imput; ancient DNA allows the researcher to identify specific species of animals and then compare those seasonality patterns with known modern patterns.
Aaris-SÃ¸rensen K, MÃ¼hldorff R, and Petersen EB. 2007. The Scandinavian reindeer (Rangifer tarandus L.) after the last glacial maximum: time, seasonality and human exploitation. Journal of Archaeological Science 34:914-923.
Blaise E, and Balasse M. 2011. Seasonality and season of birth of modern and late Neolithic sheep from south-eastern France using tooth enamel d18O analysis. Journal of Archaeological Science 38(11):3085-3093.
Crawford GW, and Bleed P. 1998. Scheduling and Sedentism in the Prehistory of Northern Japan. In: Rocek T, and Bar-Yosef O, editors. Identifying Seasonality and Sedentism in Archaeological Sites: Old and New World Perspectives. Cambridge, Massachusetts: Peabody Museum, Harvard University.
Cross JR. 1988. Expanding the scope of seasonality research in archaeology. In: Huss-Ashmore R, editor. MASCA: Coping with Seasonal Constraints. Philadelphia: University of Pennsylvania. p 55-63.
Deith MR. 1983. Molluscan calendars: The use of growth line analysis to establish seasonality of shellfish collection at the Mesolithic site of Morton, Fife. Journal of Archaeological Science 10(4):423-440.
Ewonus PA, Cannon A, and Yang DY. 2011. Addressing seasonal site use through ancient DNA species identification of Pacific salmon at Dionisio Point, Galiano Island, British Columbia. Journal of Archaeological Science 38(10):2536-2546.
Hufthammer AK, HÃ¸ie H, Folkvord A, Geffen AJ, Andersson C, and Ninnemann US. 2010. Seasonality of human site occupation based on stable oxygen isotope ratios of cod otoliths. Journal of Archaeological Science 37(1):78-83.
Humphreys AJB. 1987. Prehistoric seasonal mobility: What are we really achieving? The South African Archaeological Bulletin 42:34-38.
Hurtado AM, and Hill KR. 1990. Seasonality in a foraging society: Variation in diet, work effort, fertility, and the sexual division of labor among the Hiwi of Venezuela. Journal of Anthropological Research 46(3):293-346.
Huss-Ashmore R. 1988. Introduction: Why study seasons? MASCA: Coping with Seasonal Constraints 5:5-7. MASCA: Coping with Seasonal Constraints. Philadelphia: University of Pennsylvania.
Rendu W. 2010. Hunting behavior and Neanderthal adaptability in the Late Pleistocene site of Pech-de-l'AzÃ© I. Journal of Archaeological Science 37(8):1798-1810.
Yerkes RW. 2005. Bone Chemistry, Body Parts, and Growth Marks: Evaluating Ohio Hopewell and Cahokia Mississippian Seasonality, Subsistence, Ritual, and Feasting. American Antiquity 70(1):241-266.
Zhao Z, and Piperno DR. 2000. Late Pleistocene/Holocene Environments in the middle Yangtze River Valley, China and rice (oryza sativa L.) domestication: The phytolith evidence. Geoarchaeology 15(2):203-222.