Time.

Time is a selfish human entity. If there is nobody around to witness time; time stops.

An idea -
If there was only one human in existence, even though time would be still be present, it would not matter. Time truly becomes meaningful only on a large scale; when many are involved. Time is used to measure successes and triumphs over other people. For instance, success is measured by how full a person’s life has been (whether this is through wealth, prosperity, fame, etc), summed up at the end; compared to another life. This all becomes possible with the constant of time added to the equation.

Now imagine if there was only one human being in existence, time would not matter because there would be no one else’s achievements to compare to. Therefore, time causes the pack to become selfish; to be better than others in the short time they are around. This may be through careers, relationships, journeys, or even religious matters. These things only matter when time (and a population of people) is introduced.

Through this 'one human' theory, we can see that such things as careers, relationships, journeys or religious ventures now become irrelevant as this human does not have a population (with a limited amount of time) racing against him/her. Now all that this human needs to do to fulfil his/her life - to succeed - is to live out his/her time. To survive until he/she cannot, until time takes over. Time would become irrelevant as there would be no need to compare these trivial human pursuits, because there would be no one to compare to.

Selfish creatures.