Complex sentence: Historically, human population control has been implemented by limiting the population's birth rate, by voluntary contraception or by government mandate, and has been undertaken as a response to factors including high or increasing levels of poverty, environmental concerns, religious reasons, and overpopulation.
Split into simpler sentences: Historically, human population control has been implemented by limiting a region's birth rate, by voluntary contraception or by government mandate. It has been undertaken as a response to factors including high or increasing levels of poverty, environmental concerns, religious reasons, and overpopulation.