Resources are unequally distributed in the world. Poor people remain poor and suffer by undernourishment and hungry. Also the medical health centers are lacking in underdeveloped countries. For example in Africa there are a lot of persons that suffer for HIV, but the developed countries do not bother to take care to that  problem. The HIV-positive women  of childbearing age reproduce and transmit the disease to newborns.

Foods are unfairly distributed so much so that in rich countries the problem of obesity is eroding the state budgets for health, while in poor countries the health interventions for prevention and treatment are sporadic.

Considering the quality, also the  food safety is not equally distributed. The economic wealth promotes both food and environmental protection. In countries in the course of industrialization, the environmental mistakes already made by the post-industrial countries are not avoided, but repeated. The handheld example is China, just see the intolerable pollution in the cities, the territorial instability caused by economic development, the explosion in the consumption of beef creates an higher "ecological and carbon footprint"  and impact on health. Poverty and wealth create both benefits and problems to which the world is not able to give to anyone an answer anywhere. This is a complex problem that everyone, and especially the scientist, has to face.

Resources are unequally distributed in the world. Poor people remain poor and suffer by undernourishment and hungry. Also the medical health centers are lacking in underdeveloped countries. For example in Africa there are a lot of persons that suffer for HIV, but the developed countries do not bother to take care to that  problem. The HIV-positive women  of childbearing age reproduce and transmit the disease to newborns.

Foods are unfairly distributed so much so that in rich countries the problem of obesity is eroding the state budgets for health, while in poor countries the health interventions for prevention and treatment are sporadic.

Considering the quality, also the  food safety is not equally distributed. The economic wealth promotes both food and environmental protection. In countries in the course of industrialization, the environmental mistakes already made by the post-industrial countries are not avoided, but repeated. The handheld example is China, just see the intolerable pollution in the cities, the territorial instability caused by economic development, the explosion in the consumption of beef creates an higher "ecological and carbon footprint"  and impact on health. Poverty and wealth create both benefits and problems to which the world is not able to give to anyone an answer anywhere. This is a complex problem that everyone, and especially the scientist, has to face.

quality of life can not be equal everywhere as far as the human kind have the same style of selfish thinking.

• The dramatic improvement in health was the discovery of DDT, which allowed a major breakthrough in attempts to control one of the major killers of children in less-developed regions of the world, malaria. Aggressive use of inexpensive DDT led to the rapid eradication of malaria in Taiwan, much of the Caribbean, the Balkans, parts of northern Africa, northern Australia, large parts of South PaciÖc, and all but eradicated malaria in SriLanka and India.
• The improvements in public health was the establishment of the World

Health Organization after World War II, which greatly facilitated the spread of medical and public health technology to poorer countries. From the 1950s, the WHO pushed public health and immunization drives (e.g., against smallpox). In conjunction with the WHO, the US military also played an important role in developing treatments for diseases like cholera

and spreading the use of DDT and penicillin.

• The change in international values, emphasizes, after the 1930s, Universal values assured that health breakthroughs in any country would spread rapidly to all others where the means for implementation existed. The consequence of the combination of these four factors was a dramatic improvement in life expectancy in much of the world, especially in the lesser developed parts of the globe, starting in the 1940s. Most of the key changes were available in almost all countries by 1950. Consequently, by the late 1940s and early 1950s, there were signiÖcant improvements in health conditions and life expectancy in Central America, South Asia and parts of Eastern and Southern Europe compared to richer countries

https://ipl.econ.duke.edu/bread/sites/default/files/0509conf/bread0509_acemoglu_johnson.pdf

Poorer families have more children in a world with an expansion of the world population size, or not?

Why do poor families (wish to) have many children [and rich families (wish to) have few children]?

Because there is what is called "greedy" profit! Let me quote from Tony Judt: 

“What matters is not how affluent a country is but how unequal it is. Thus Sweden, or Finland, two of the world’s wealthiest countries by per capita income or GDP, have a very narrow gap separating their richest from their poorest citizens—and they consistently lead the world in indices of measurable wellbeing. Conversely, the United States, despite its huge aggregate wealth, always comes low on such measures. We spend vast sums on healthcare, but life expectancy in the US remains below Bosnia and just above Albania.”

Excerpt From: Judt, Tony. “Ill Fares the Land.”  

@ Marcel

Agree that that the poor families have more children and there the family planning is not in their living style,  for want of

• Avenue to occupy themselves in other activities
• Lesser demands of life and
• Such is the environ and life style/ culture
• In some clan / community - that is a norm or average family size

Money can be a cruicial factor in improving the quality of life, but its role in happiness is less. Money can help but it does not mean or create happiness.

I believe that the responsibility of medical science and other parties and associations for providing clean and healthy food has increased life expectancy.

At present, the world is ruled by materialistic capitalist systems under the auspices of governments that believe in gaining military power & monetary power by any means. There is no place for ethics or humanistic outlook in the current politics. The world is divided into masters “the haves” & slaves “the have-nots”. Therefore, the quality of life will differ between the “over-fed” & the “seekers of a piece of bread”. Emotional calls will only fall on deaf ears of obstinate politicians in the influential countries “who think that they are always right”.

Neither money nor the military might “which protects it or paves the way for its increase” can bring happiness. What brings tranquility “which leads to happiness” are the spiritual & moral values which emphasize justice, giving, and love or care for every human being & not for a particular “super” race.

Who would like to re-experience the conditions from 200 years ago?

We have to look ourselves at the mirror and accept that many problems arise from  our cynical way of thinking. (And I do not refer to RG community, on the contrary, people here are a kind of oasis in the desert)