Determination of the pattern of nuclear binding from the data on the lepton nucleus deep inelastic scattering
Nucleon structure function ratios r(x) = F2A(x)/F2D(x) measured in the range of atomic masses A larger or equal 4 are analyzed with the aim to determine the pattern of the x and A dependence of F2(x) modifications caused by nuclear environment. It is found that the x and A dependence of the deviations of the r(x) from unity can be factorized in the entire range of x. The characteristic feature of the factorization is represented with the three cross-over points x_i, i = 1 -- 3 in which r(x) = 1 independently of A. In the range x lager than 0.7 the pattern of r(x) is fixed with x_3 = 0.84 +/- 0.01. 
The pattern of the x dependence is compared with theoretical calculations of Burov, Molochkov and Smirnov to demonstrate that evolution of the nucleon structure as a function of A occurs in two steps, first for A less or equal 4 and second for A larger than 4. The long-standing problem of the origin of the EMC effect is understood as the modification of the nucleon structure in the field responsible for the binding forces in a three-nucleon system.