Excerpt from executive order 9066 by virtue of the authority vested in me as president of the united states, and commander in chief of the army and navy, i hereby authorize and direct the secretary of war: to prescribe military areas in such places and of such extent as he or the appropriate military commander may determine, from which any or all persons may be excluded, and with respect to which, the right of any persons to enter, remain in, or leave shall be subject to whatever restriction the secretary of war or the appropriate military commander may impose in his discretion. - president franklin delano roosevelt, 1942 the purpose of this declaration by president roosevelt was to a) prevent japanese spies from causing harm to the united states. b) prevent african americans from enlisting in the army. c) imprison german americans during world war i. d) create jobs in the american military.

answer:   migrations were important in the neolithic period. "two major migrations passing through southeastern europe were confirmed by the means of archaeo-genetic studies."

the first migration was the early neolithic period -- 6,000 before common era (bce) -- when the first farmers, from anatolia -- asia minor -- spread through europe. the second migration occurred during the early bronze age (3,000-2,500 bce) when the so-called "steppe population," from the eurasian steppe, replaced much of northern europe's previous population.

the first farmers of northern and western europe passed through southeastern europe with limited hunter-gatherer genetic admixture, which occurs when two or more previously isolated populations begin interbreeding. however, some groups that remained mixed extensively -- without the male-biased, hunter-gatherer admixture that prevailed later in the north and west, according to latest discoveries. southeastern europe continued to be a nexus between east and west, with intermittent genetic contact with the steppe people up to 2,000 years before the migrations that replaced much of northern europe's population.

"in some places, hunter-gatherers and incoming farmers seem to have mixed very quickly," says iain mathieson, a geneticist at the university of pennsylvania, who was first author of the paper. "but, mostly, the two groups remained isolated, at least for the first few hundred years. these hunter-gatherers had been living there for thousands of years, and it must have been quite a shock to have these new people show up -- with a completely different lifestyle and appearance."