4. DNA rarely helps to connect arch

4. DNA rarely helps to connect archaeology with language. Language boundaries and material culture boundaries coincide under some circumstances, but these ethnolinguistic frontiers are almost never genetic—people marry across them. Material-culture frontiers that persist in one place over many centuries are usually ethnolinguistic. This happens at sharp ecological boundaries, where contrasting subsistence, settlement, and prestige systems generate a cultural frontier that can persist for long periods. Persistent ethnolinguistic frontiers also occur at the edges of regions recently colonized by substantial numbers of long-distance migrants (Brittany/France, England/Wales, French/German Switzerland).The ecological frontier between the river deltas of southern Central Asia/Iran and the deserts and steppes was a persistent cultural-economic boundary between 5000 and 1500 b.c. and therefore probably a linguistic frontier as well. Given their core vocabulary of ecological terms,Indo-European languages had to originate north of this line, but the spread of Indo-Iranian languages southward after 1650–1500 b.c. seems to have resulted in the replacement of the earlier urban tradition with an assortment of pastoral regional groups, not one intrusive culture. The principles that connect language and material culture are complicated and not applicable to every situation. Still, it is by investigating such principles (see,e.g., Cordell 1997, chap. 11), rather than depending on the false hope of DNA, that we will increase our understanding of the archaeology of language.