In fact, if more women decide to have children on their own, the single-parent household may become more typical than the traditional family in many countries. Also, unmarried couples may decide to have more children--or they might take in foster children or adopt. And because people are staying single and living longer (often as widows), there may be more one-person households. On the other hand, some people believe similar events happen again and again in history: if this is true, people may go back to the traditional extended or nuclear family of the past. Others think the only certainty in history is change: in other words, the structure of the future family could begin to change faster and faster--and in more and more ways.