99.xx% of the time we wouldn't need any blood test, as it would be visibly apparent. But yes, a test would also confirm the same thing. You can mine genetic data not only from blood, but also saliva, hair, nails, skin, etc. btw. And no, we wouldn't need any genetic testing to confirm that Germans and Englishmen are of the same racial group- just as we wouldn't need any such testing 99.xx% of the time to make a distinction between a black and white person. It's kind of ironic, Germans and English are perhaps two of the most closely related groups of Europeans in existence; The Angles, Saxons, and Jutes (now collectively called "Anglo Saxons", mostly came from modern day Germany. What's left of the original Brython genetic stock is mostly in whales, which managed to insulate itself from the Anglo Saxon invaders during the 5-6th century. <iframe width="425" height="349" src="http://www.youtube.com/embed/j617mImHVvk" frameborder="0" allowfullscreen></iframe>