Can someone please help me with pointers on how to start answering this: How has prehistory art influenced 20th century art?
[eNotes policy allows you to ask only one question, so I edited yours. You can post the other two as two separate questions to get answers to those.]
When referring to pre-historic art, specifically, the first example that I would direct you to would be the cave paintings of Lascaux, France.The images may in some ways be simple and undefined, yet it is very easy to see what the painter was depicting. The need to record events and express to others what one has seen is an impulse that would seem to have been inherent in human nature from the beginning of human activities. Therefore I would say one influence of the initial need to communicate and inform, has developed into an artistic impulse in the present day. The need for pictorial messages may be far less necessary but our need for artistic expression is as strong as ever.
The invention of photographic images was the start of modern abstract art and other styles that were less representational. This means that people began to make art that was less and less concerned with making images that looked exactly like what they saw. As this trend developed artists grew to prefer simpler forms to give a viewer an impression of an idea rather the the thing itself. Allowing the viewer to use imagination and their own memories to inform what they saw. Artists such as Henri Matisse and Pablo Picasso are two well known artists that have drawn on ancient pre-historic images to create their own modern interpretations. If you look at the attached links and images you will be able to see the relationships between the old and new. Simpler forms, colors that are intended to create emotional response not intended to be accurate portrayals of things seen and a move back to flat, two dimensional images rather than trying to create the illusion of depth.