So oil has little to do with population growth. That's only if you ignore some key facts. People in third world countries consume food grown in countries with mechanized agriculture. There is such a thing as a global food market. This is why US efforts to divert corn into ethanol production led to steep corn prices increases in Mexico and elsewhere. (This is regardless of the fact that ethanol corn is typically not human food corn).
Here is an interesting report on why Africa is net food importer:
http://www.fao.org/docrep/015/i2497e/i2497e00.pdf$this->bbcode_second_pass_quote('', 'T')hat Africa has become a net importer of food and of agricultural
products, despite its vast agricultural potential, is puzzling. Using
data mainly for the period 1960-2007, this report seeks to explain Africa’s
food-trade deficit since the mid-1970s. The core finding is that population
growth, low and stagnating agricultural productivity, policy distortions,
weak institutions and poor infrastructure are the main reasons. A typology
of African countries based on data between 2000 and 2005 reveals that the
state of food import dependency is different across the continent and varies
according to countries’ levels of income. Although the few and relatively rich
countries in Africa had the highest net food imports per capita (USD 185 per
year in real terms), they had ample means to pay for their food import bills
using revenue from non-agricultural sources. Conversely, the majority of the
Africa’s low-income countries (mostly in Sub-Saharan Africa), where twothird
of its population lives, had been net food importers; they imported far
less food per capita (USD 17 per year) but had difficulty covering their food
imports bills, as their export revenues were limited. Overall, between 1980
and 2007, Africa’s total net food imports in real term grew at 3.4 percent per
year, but this growth was mostly fuelled by population growth (2.6 percent
per year)