Chicago, Illinois, USA is another place, where evolution in the making can be watched, besides Allen’s rule being observable in Western Australia. Researchers of the Field Museum in Chicago compared samples of eastern chipmunks (Tamias striatus) and of eastern meadow voles (Microtus pennsylvanicus), that got collected in Chicago since more than 125 years. During that time span the size of the skulls of the eastern chipmunks increased while the size of their teeth decreased. During the same time span did the inner ears of the eastern meadow voles, too, become smaller. The researchers presume that smaller inner ears make the eastern meadow voles less susceptible to noise. These changes are consequences of the urbanization of the living environment of those animals. But whether these changes are advantageous adaptations still is only speculative.