Evidence presented in his work suggests how we might make such a connection.These indentured servants were treated as slaves for the period during which they had sold their time to American employers.

• 对于那些数量保持相对不变，或者以一种循环周期进行摆动的种群而言，这种“信号”将会相当容易提取特征并描述它的影响，即使我们仍不知道作为原因的生物机制。