For prehistory, Forster and Renfrew (2011) argue that in some cases there is a correlation of language change with intrusive male Y chromosomes but not with female mtDNA. They then speculate that technological innovation (transition from hunting-gathering to agriculture, or from stone to metal tools) or military prowess (as in the abduction of British women by Vikings to Iceland) causes immigration of at least some males, and perceived status change. Then, in mixed-language marriages with these males, prehistoric women would often have chosen to transmit the "higher-status" spouse's language to their children, yielding the language/Y-chromosome correlation seen today.