Do Ashkenazi Jews have more Middle Eastern ancestry or more European ancestry? And is this difficult to determine because European peoples have a fair amount of Midde Eastern and North African ancestry?

Everything I've read seems to say that the only things that cause the split between those populations are the Mediterranean Sea and the Caucus Mountains and in terms of DNA, Middle Eastern, North African and European sort of clump together.

That whole issue of a population split caused by the Mediterranean Sea seems strange because the barrier that apparently separates North African from sub-Saharan African populations is the Sahara Desert and this presumably has caused a greater genetic difference, even though large bodies of water are apparently a more formidable barrier to gene flow than mountains, deserts, and harsh landscapes with little food or water.

there certainly are clear and reproducible genetic differences between the 2 groups that imply differences in the original locations of the groups. Of course admixture between them and with other local groupings over time is inevitable. See the links below for 2 good papers that should both be available to you.

http://link.springer.com/article/10.100 … 012-1235-6
http://www.sciencedirect.com/science/ar … 9707613251