Within the theory of evolution, a "positive" or favorable trait is one that

In the theory of evolution of Charles Darwin, it is stated that the evolution is driven by a positive trait, or also known as the positive mutation.  In the natural selection, which is the process of selecting organisms that suited best to their respective environment and known to reproduce more successfully compare to other organisms, suggests that the positive mutations drive the natural selection.  Charles Darwin made a proposal of natural selection as the mechanism of driving evolution.  In this proposal, it stated that the phrase positive mutations drive natural selection means that the evolutionary changes over the populations and generations. 

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.