http://en.wikipedia.org/wiki/Haplogroup_J1_(Y-DNA) 
Please review the map, the work of Tofanelli et al, Hassan et al,  and comment in the discussions:
http://en.wikipedia.org/wiki/File:HG_J1_(ADN-Y)
http://hpgl.stanford.edu/publications/AJHG_2004_v74_p1023-1034.pdf
http://ychrom.invint.net/upload/iblock/94d/Hassan%202008%20Y-Chromosome%20Variation%20Among%20Sudanese.pdf
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC384897/figure/FG1/
http://en.wikipedia.org/wiki/Haplogroup_J1_(Y-DNA)
http://en.wikipedia.org/wiki/Talk:Haplogroup_J1_(Y-DNA)
Essentially, the issue is whether J1 dominates in Sudan and the Caucasus at over 60%. 
John Lloyd Scharf