Man’s first real invention， one of the most important inventions in history， was the wheel. All transportation and every machine in the world depend on it.
The wheel is the simplest yet perhaps the most remarkable① of all inventions， because there are no wheels in nature—no living thing was ever created with wheels. How， then， did man come to invent the wheel？
Perhaps some early hunters found that they could roll the carcass② of a heavy animal through the forest on logs more easily than they could carry it. However， the logs themselves weighed a lot.
It must have taken a great prehistoric thinker to imagine two thin slices③ of log connected at their centers by a strong stick. This would roll along just as the logs did， yet be much lighter and easier to handle. Thus the wheel and axle④ came into being， and with them the first carts.
① remarkableadj. 值得注意的，非凡的，卓越的
② carcassn. (动物的)尸体
③ slicen. 薄片，切片，片[(+of)]
④ axlen. (机器的)轴
人类的第一项真正发明
轮子是人类第一项真正的发明，也是历史上最重要的发明之一，世界上的一切交通工具和每一部机器都有赖于它。
在一切发明中，轮子是最简单的，然而也许是最了不起的一项发明，因为自然界中没有轮子——带轮子的生物还没有被创造出来过。那么，人类是怎样发明轮子的呢？
也许是一些早期的猎人发现了这一点：依靠圆木的滚动，把沉重的动物尸体推出森林，比肩扛背驮要容易。不过，圆木本身也够重的了。
这一定使一位史前的伟大思考者产生想象，用一根结实的棍棒把两块圆木的薄片从中心连接起来，这玩意儿也恰恰像圆木一样能向前滚动，不但要轻得多，而且更容易驾驭。这样轮子和轴便应运而生，随之出现了第一批手推车。
