  A system of nonlinear ordinary differential equations with forcing function
is developed to model evolution processes in complex systems. In this system R,
C, and P are the resource, consumption, and production functions
correspondingly. F is the forcing function. Two cases F=0, and F=A+Bsin(omega x
t) are considered. It is shown that if F=0, there exist an unstable periodic
solution for a certain set of system coefficients. In the case of periodic
forcing, system has an attractor solution. The system developed may have a wide
range of applications: in biological and social sciences, in economics, in
ecology, and, as well, in modeling climate. A correspondence between the
theoretical (numerical) solution and Late Pleistocene climate data dynamics is
analyzed on a qualitative level.
