Darwin believed that Malthus's hypothesis about population growth and limited resources applied to all living organisms, including humans. Malthus's theory, often referred to as Malthusianism, proposed that populations tend to grow exponentially while resources such as food and space increase at a slower rate. Darwin saw this principle as a key component of natural selection, where individuals with advantageous traits have a better chance of survival and reproduction, while those with less favorable traits are more likely to struggle or perish due to competition for limited resources.