Introduction

During the last four centuries, millions of Scots have left the British Isles as a result of push factors including overpopulation, religious persecution, and political and economic upheaval. Many of these individuals found their way to the Americas, where the promise of land and opportunities in trades such as tobacco, sugar, and textiles offered a better way of life and outweighed the costs and dangers of a trans-Atlantic journey (Landsman, 1999). Scots began to arrive in the American colonies during the 1600s, and have contributed much to the American culture that exists today. In the 2006 American Community Survey, the United States Census Bureau reported over 6 million Americans (1.7% of the total population) claimed Scottish ancestry. Another 5.3 million (1.5% of the U.S. population) claimed a Scotch–Irish ancestry, a term usually indicating descent from the estimated 100 000 Scots that left the Scottish lowlands for the Irish Province of Ulster during the 1600s, and migrated to North America some five generations later (Houston, 1996). There are an estimated 24 million (estimated from D.A. Bruce, 1998) or so individuals around the world who claim Scottish ancestry despite having never seen Scotland itself. How and why an individual identifies with a particular ethnic group after being removed from their “homeland” for several generations has long been a perplexing question. This chapter describes the movement of Scots to the Americas, the genetic structure and diversity seen within Scotland, and presents the maternal and paternal genetic markers of a group of Americans who claim Scottish ancestry, to show how molecular markers can be used to illustrate the migratory behaviors of humans.

Causes of migration to the Americas

Immigration to the New World colonies began in the 1600s and by 1700 some 6000 Scots had arrived (Fogleman, 1992; Houston, 1996).