Silver Birch (IMAGE) University of Helsinki Caption The last ice age split the birches into two populations, a European and a Siberian one, which have been mixing in Finland since the melting of the continental ice sheet. Credit Jarkko Salojärvi Usage Restrictions Credit: Jarkko Salojärvi License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.