Genetics and Gathering the House of Israel

My patriarchal blessing indicates that I am a literal descendant of Ephraim and heir to specific blessings and promises. But what does this statement mean? How could someone like me, whose genealogy, 23andMe, and AncestryDNA results all show 100 percent European, be a literal descendant of someone who lived thousands of years ago in the Middle East? And how does this relate to the doctrine of the gathering of Israel? Growing up I heard many statements about the “lost tribes,” the mysterious story of the disappearance of the ten northern tribes of Israel after the kingdom was sacked by the Assyrians around 720 BCE. Over time, legends developed that one day they would be rediscovered and rejoin the Jews. My Sunday School and seminary teachers seemed to suggest that there would be some isolated ethnic group that missionaries would discover, and they told anecdotes about different cultures, highlighting similarities to Hebrew culture and symbolism. Some millennialist Christians have even identified groups they claim to be lost Israel. Although such claims are unlikely, this kind of teaching gave me the impression that the lost tribes would be identified as groups—someone would proclaim, “This is clearly the lost tribe of Issachar (or Zebulon, or Gad). Check another one off the list.” To my naïve