这句话为什么用过去时啊？

Until recently, the Inuit people led a nomadic existence, sheltering in
        igloos, the ice-block domes that are peculiar to north-central Canada,
        and in structures made of stones, bones, driftwood, and skins.

这句话为什么用过去时啊？

用现在完成时的那个选项吗？

    呵呵 那我就选对了 Thanks！