J.S. Alho and colleagues argued in 2011 that, although Allen's rule was originally formulated for endotherms, it can be applied to ectotherms which derive body temperature from the environment. In their view, ectotherms with less surface to volume would heat up and cool down more slowly, and this resistance to temperature change might be adaptive in "thermally heterogeneous environments". Alho said that there has been a renewed interest in Allen's rule due to global warming and the "microevolutionary changes" that are predicted by Allen's rule.[5]