How Inventions of the Stone-Age became the Foundation of the Principles of Engineering

In the previous posts,  the the history of Mechanical Engineering had been touched upon. There is a need to revisit the invention of the first ever machine, known as a tool now a days, to get the depth of basic principles upon which the foundation of Mechanical Engineering has been built and such a tremendous growth has come about, 

You have already seen this picture of a tool made from stone. The same is being reproduced here with a white boundary  drawn along its borders indicating its resemblance to an axe. This is an axle without a customary handle.  

This Axe like tool must have been made by using some stones, which had been harder, in order to cut this particular stone.  The key to the success of this invention was the sharpness  of the cutting edges. This invention was not a result of well planned experiments or any kind of research behind it. This must have been achieved after so many trials and errors. The basic purpose behind this invention was to produce a Sharp-Edge. 

The very idea of Sharp-Edge bring us to the concept of Angles. The invention, therefore, becomes immensely significant. You will appreciate, without the concept of Angle,  the evolution of initially geometry and subsequently trigonometry would not have been possible. 

It is very important to clearly understand and ingest in our minds the  concept of angles or slopes or gradients, whatever you call it. Without the clear concept of an angle or a slope it is not possible to understand Mathematics, Physics and Engineering Drawing. The simplest example of the use of  the concept of an angle is a ramp. The figure of a ramp is shown below:  

The ramp essentially consists of a base, also called Run, then there is the height also called Rise and finally there is a line joining the two end which is known as the Slope.