In preparation for winter, the common shrew ( Sorex araneus ) shrinks its brain by 30 percent to conserve precious energy. Then, come spring, the shrew miraculously 'regrows' its shrivelled brain, neurons fully intact. Scientists have now traced the evolutionary origins of this rare adaptation and the genes that likely enable it. While fascinating in its own right, this information may also spark new approaches to understanding and treating human brain degeneration . The unusual adaptation is