Both humans and monkeys have this. A VERY long time ago Humans had very small "strings" of skin. This skin has evolved over time and now there is a bone left. Monkeys are technically un-evolved humans. Good thing they stuck around.
Answer:
The survival and reproductive success of an individual is directly related to the ways it's inherited traits function in the context of its local environment
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Two things that INCREASE population, would be an increase in leisure space. Another is if the area is sustainable for life. Two things that would DECREASE population, would be a scarcity of any required resources. A decrease in space, and not a sustainable area.