The development of the countries does not really affect the population. Look at China. China is still very much underdeveloped compared to America, but yet it has 2x as many people as America and makes up 1/4 of the human population.
The earth is has a temperature and is characterized by the system of the heat budget that acts as a balance to the flow of the heat with the earth's latitudes.
Thereby it keeps the earth warm form within and also filters the UV radiation and also provides water in the form of the rain.
The entire atmosphere act as a filter to the solar radiation that falls on the earth and thus acts shield to protect the planet.
