He has also studied broader biological problems such as evolutionary theory, the principles of phylogenetics, taxonomy, nomenclature, and palaeoecology.

In 1967 he received his Ph.D. in biology from the Paleontological Institute with the thesis "The Mesozoic Hymenoptera Symphyta and the early evolution of Xyelidae".

[2] He is one of the foremost authorities on the paleontology and systematics of Hymenoptera whose ideas have formed the foundation of the modern classification of that insect order.

According to him, the wings first evolved, as a means to control gliding, in relatively large insects that had turned to feeding on generative organs of arboreal plants.

He develops an alternative approach to biological systematics, called “phyletics”, which differs from phenetics in taking into account genealogy in addition to similarities and hiatuses.

[2] He also contributed significantly to the epigenetic theory of evolution and, in particular, has put forward the concept of “adaptive compromise” and the notion of macroevolution being irreducible to microevolutionary processes alone.

[2] Rasnitsyn has also made a significant contribution to paleoecology and in collaboration with Vladimir Zherikhin developed the theory of ecological crises.