This is part of the lore of the Northern people. There are thousands of such stories told by cultures both ancient and modern, from the Old Testament to the interior of the Amazon today.
Humans in their tribal state were extremely ethnocentric, and often their various groupings bear names that mean something like "the true people" or "the real human beings" to distinguish themselves from their neighbors. Likewise, their creation myths tend to be ethnocentric and to pertain only to themselves - not to all of humankind, with which they are not particularly concerned.
To argue that all humans are descended of Ask and Embla is to say that the myths of every other native culture are wrong, and that only ours is right. From the Australian Outback to the depths of Africa, groups have their own explanations for how they came to be. It is the
height of arrogance to assume that our stories apply to them, and that the sacred tales of their own people are false. Unless we assume that their lore is inferior and inaccurate, we are forced to the logical conclusion that each group is right - so long as it speaks to its own people, and no other.
Indeed, to say that our creation story is the only true one is to deny the existence and validity of other peoples' Gods - for it imposes Odin, Hoenir, and Lodur upon these other folk, shoving their Gods rudely out of the picture and negating their own religious explanations for the nature of things. Most Asatruar would not support such religious imperialism. To say that ours is the "one, true" story of human origin smacks not only of religious intolerance but...well, racism!
Free eBooks (Can Be Downloaded):
Anonymous - Pagan Stones And GemsAnonymous - Pagan Germany
Emmanuel Swedenborg - Heaven And Hell
Albert Pike - Morals And Dogma