A hedgehog is any of the spiny mammals of the subfamily Erinaceinae and the order Erinaceomorpha. There are 17 species of hedgehog in five genera, found through parts of Europe, Asia, Africa, and New Zealand (by introduction). Hedgehogs share distant ancestry with shrews (order Soricidae), with gymnures possibly being the intermediate link, and have changed little over the last 15 million years. Like many of the first mammals they have adapted to a nocturnal, insectivorous way of life. Hedgehogs' spiny protection resembles that of the unrelated rodent porcupines and monotreme echidnas.