What Causes Change

Change will happen as long as the universe exists. There are many types of changes and one would be changes that are caused by the need for change. If you were to participate is modern warfare with stones and mediocre bows and arrows, you wouldn't get very far. The situation requires for you to change and adopt the use of more effective weaponry such as guns, airplanes, tanks, etc.
Another example of change would be evolution. Basically, all helpful traits that are useful for survival and reproduction become increasingly common and those traits that are no longer useful to survival and reproduction become obsolete. Slowly but surely, this creates considerable change in the world we live in. For more information on evolution, click here.
Change by need can be traced down to the sub-atomic level as well. All atoms want to be "happy" and in order for that to happen, their valence shell has to be complete. Non-metal atoms form covalent bonds with one another in order to satisfy their need and create completely new substances because of it. Here is a crudely drawn example of an a chemical compound. .

Notice that each valence shell is complete. This is sugar for those who don't know.
There are other ways change can be caused. It could be caused by another object. When you kick a ball, you transfer energy to the stationary item and cause motion. On a larger scale, if a meteor were to hit the Earth, that would quite a large energy transfer and it would cause a major change. I would also, in this section, talk about global warming but it is a controversial issue so I'll avoid it.
Those are my thoughts on what causes change.