According to Evolution the first humans appeared about 100,000 years ago. The population quickly grows to about 1,000,000, but because they were supposedly hunter - gatherers, for 100,000 years; that's 4,000 generations; the population was limited by land area. This cap was removed by the innovation of farming.
So how many stone age graves should there be? Consider 4,000 generations times 1,000,000 people, equals 4 billion people. However only thousands have actually been found. Now the bodies may have decayed; not even leaving bones, but they were buried with their stone tools, so these should still be around.
The only real explanation is that the so called stone age lasted less 100,000 years. The number of graves discovered is constant with about 500 years. This time could have been during the post