I have read but what is it about?
"abnormal" means "not normal" - so it can mean "not standard" -therefore if someone is developing at a different rate than most of the people you could say that they are not developing in a standard way - so you could say that they are developing abnormally. The sentence is correct, although it might not be the best word to use.
<span>Many intellectuals and many of those working in development believe that the size of the world's population and its accelerated growth is the greatest problem and the gravest threat to humanity. Clearly, the ratio of the number of people to the amount of food available has an impact on nutrition, but how do these two factors interact? At the end of the eighteenth century the British political economist Thomas Malthus speculated that population growth could soon surpass production and food supply. By the end of the twentieth century, this had not happened, but malnutrition was widespread.</span>
