Why do some cultures practice genocide?

1.What cultures practice genocide?
2.How many people are killed in a genocide?
3.What causes genocide?

What do you already know about your topic?

I know a little bit about the Rwanda Genocide. I learned that the Hutu President's plane was shot down and that's how the genocide began. I also know that many Tutsis died in this genocide. I also know about the Holocaust and that Hitler wanted to eliminate Jews.