But the recent studies are the first to suggest that a similar mechanism may operate in humans.

Much more research is necessary to provide a better understanding of which mechanisms actually operate and are effective in practice.

This mechanism is powerful and can operate over a short time scale.

It is quite possible that all three mechanisms might operate.

It is important to keep in mind that these two mechanisms of outbreeding depression can be operating at the same time.

Even if these descriptions are valid they still leave open a number of questions, particularly why the same mechanisms do not operate with girls.

The mechanism was operating, but the ships of the enemy did not disappear.

A general model for how this mechanism might operate is shown in Fig.

Until recently, the mechanisms were external and only operated along straight lines.