1. The bat emits these ultrasonic pulses, very high pitch sound waves that we cannot hear. 蝙蝠会发出我们听不到的非常高的超声波脉冲。
2. So the bat sends out these pulses, very focused bursts of sound, and echoes bounce back. 所以蝙蝠发出这些脉冲，一种非常集中的声波，然后回声就会反弹回来。
3. This perspective makes sense if you simplify the workings of a complex brain, reducing it to an array of electrical pulses. 如果把复杂大脑的运作机制简化为一系列电脉冲，那么这种观点就讲得通了。
4. Then, about 7000 B.C., within the space of a few generations, they switched abruptly to herding domesticated goats and sheep and to growing einkorn, pulses, and other cereal grasses. 后来，大约在公元前7000年，在几代人的时间里，他们突然转向放牧家养的山羊和绵羊，转而种植单粒小麦、豆类和其他谷类牧草。
5. They both felt their pulses beat faster. 他们都觉得脉搏跳得更快了。
