aggression is the instince in human beings and animals. Actually, human being is also a category of animal, even the most violent one. Animals fight each other for their territory, while, human beings also fight for this reason, this is the similarity. The resource on this planet is very limited, therefore, compared with the fighting among animals and fighting with human beings have great differences. The fighting among animals may not occurred death among one species, only for food, some deaths may occured; However, when a war break out, many people would die, and the environment may be destroyed greatly. Our human beings should learn to animals, stop fighting with each other, and endeavor to protect the environment, conserve the limited resources. If human beings are not so cruel, the world would be changed greatly.