Before revision:  It is revealed that the so-called memory concept of the fractional derivative damps out oscillations in the population numbers so that the system as a whole settles on a equilibrium quicker than it would with integer time derivatives  .
After revision:  It is revealed that the so-called memory concept of the fractional derivative damps out oscillations in the population numbers so that the system as a whole settles on a equilibrium quicker than it would with integer time derivatives . Finally, some possible physical explanations are given for the obtained results. It is shown that the stability requires the memory concept in the model .