The response to that is that if you remove the specific pressure on polio it will simply bounce back.

对于此观点的回应是如果你对小儿麻痹症疏忽大意它将会轻易的恢复活力。

When a bird species doesn’t face specific pressures to fly, it can stop flying in as quickly as a few generations.

当一种鸟类没有面临特定的飞行压力时，它可以在几代之后停止飞行。