<P> Although many of the Middle Woodland cultures are called "Hopewellian," and groups shared ceremonial practices, archeologists have identified the development of distinctly separate cultures during the Middle Woodland period . Examples include the Armstrong culture, Copena culture, Crab Orchard culture, Fourche Maline culture, the Goodall Focus, the Havana Hopewell culture, the Kansas City Hopewell, the Marksville culture, and the Swift Creek culture . </P> <P> The Center for American Archeology specializes in Middle Woodland culture . </P> <P> The late Woodland period was a time of apparent population dispersal, although populations do not appear to have decreased . In most areas construction of burial mounds decreased drastically, as well as long - distance trade in exotic materials . At the same time, bow and arrow technology gradually overtook the use of the spear and atlatl, and agricultural production of the "Three Sisters" (maize, beans, and squash) was introduced . While full scale intensive agriculture did not begin until the following Mississippian period, the beginning of serious cultivation greatly supplemented the gathering of plants . </P> <P> Late Woodland settlements became more numerous, but the size of each one (with exceptions) was smaller than their middle Woodland counterparts . The reasons for this are unknown, but it has been theorized that populations increased so much that trade alone could no longer support the communities and some clans resorted to raiding others for resources . Alternatively, the efficiency of bows and arrows in hunting may have decimated the large game animals, forcing the tribes to break apart into smaller clans to better use local resources, thus limiting the trade potential of each group . A third possibility is a colder climate may have affected food yields, possibly affected by Northern Hemisphere extreme weather events of 535--536, also limiting trade possibilities . Lastly, it may be that agricultural technology became sophisticated enough that crop variation between clans lessened, thereby decreasing the need for trade . </P>

When did archaic hunter-gatherers of the eastern woodlands begin to develop agriculture