Their mitochondria , unlike those of the ashkenazim , give no sign of a recent bottleneck . Their dna show instead how porous the boundaries of faith may be .
Researchers argue that it 's highly unlikely that mutated genes responsible for these illness could have reached such high levels in ashkenazim if they were not connected to cognitive performance .
His argument is that the unusual history of the ashkenazim has subjected them to unique evolutionary pressures that have resulted in this paradoxical state of affairs .