The Inclined Plane

• The inclined plane or "ramp" is probably the oldest of all the simple machines, and probably stretches back to the first time proto-man stood up on his hairy little legs and realized that it was harder to walk uphill than downhill. You could make the argument that the ramp is the basis for all machines aside from the lever, so it seems like a logical place to start.
  
  

The Wedge

• A wedge or blade is simply a combination of two inclined planes placed back-to-back, or can be a single inclined plane on a perfectly flat surface. Since the blade itself is in fact a wedge, you could trace it back to the first human analogs with their hand-axes made of volcanic glass and bone. However, the wedge as we know it today -- as a means for splitting two objects -- goes back at least to the stone quarries of ancient Egypt, over 5,000 years ago. The earliest examples though, obtained in India and Mesopotamia, are at least 9,000 to 12,000 years old.
  
  

The Wheel

• The first documented wheels date back to Iraq -- then Ur -- at or about 3,500 BC. The wheel and axle and the horse-drawn chariots that they spawned were a major driving force behind the Persian empire from about 3,500 to 1,000 BC. The wheel as a load-bearing mechanism is itself descended from the inclined plane; it's really just an infinite number of inclined planes with matching angles, placed end-to-end to create a circle.
  
  

The Pulley

• The pulley, by necessity, followed the wheel. The Greeks first mention use of the pulley during the fourth century BC, but it was probably around long before that. Being an evolution of the wheel, it stands to reason that it probably didn't lag far behind its forefather in terms of development. The first pulleys were likely immobile: just a rope tossed over a tree branch or horizontal beam, but later wheel-type compound pulleys almost certainly saw use in quarrying the stone for and in building the Great Pyramid of Giza, around 2,560 BC.
  
  

The Lever

• While levers weren't fully described and quantified until Archimedes came along in 260 BC, they had been around in one form or another long before. If you're going to draw a line to divide the "families" of simple machines, then you have to put the lever on its own. In many ways, every machine on Earth derives either from the lever, the inclined plane or both.
  
  

Screws and Gears

• If you think of all simple machines as being either in the "lever" family or the "inclined plane" family, then you have to look at gears and screws as cousins of a sort. A screw is just a shaft -- essentially a very thick wheel -- with an inclined plane that starts at the bottom and winds its way up. The first "gears" were wheels with short levers or knobs sticking out of the sides. These levers fit into holes on a matching wheel, locking the two together in rotation. From there, it doesn't take too much imagination to see how this design would have evolved into the matching-tooth mechanism we know today.