Answer
The evolutionary explanation for sibling rivalry--especially in the teenage years--is rather simple. Up until their teenage years, children are completely dependent upon their parents. They depend upon parental figures for everything, including food, shelter, emotional support, and protection. When there are more children in a family that are younger than their teen years, they are all competing for these resources. As a result, children compete with each other in a primal attempt to have better access to these resources. When children leave the teenage years and become more independent, this rivalry lessens as the children are able to provide more of these resources for themselves.
Work Step by Step
The evolutionary explanation for sibling rivalry--especially in the teenage years--is rather simple. Up until their teenage years, children are completely dependent upon their parents. They depend upon parental figures for everything, including food, shelter, emotional support, and protection. When there are more children in a family that are younger than their teen years, they are all competing for these resources. As a result, children compete with each other in a primal attempt to have better access to these resources. When children leave the teenage years and become more independent, this rivalry lessens as the children are able to provide more of these resources for themselves.
