According to the theory of natural selection, organisms which are better suited for their surrounding environment have higher chances to survive and reproduce as compare to organisms which are poorly suited for their surrounding environment.
Darwin gave theory of natural selection and stated that all living organisms show variations, which are essential for evolution of a new species. Hence, it is known as theory of evolution by natural selection.
Before puberty, children do have an estrogen level in their body. This is only truly noticeable around the time of puberty. It's always there, but not hyperactive until puberty.
