Listing previous answers is just a convenience (and takin' the slow boat to flair). It is not an attempt to shut down discussion. More questions and discussion are welcome.

For Africa specifically, you can see the FAQ section 'Why is Africa "less developed"?' at https://www.reddit.com/r/AskHistorians/wiki/africa#wiki_why_is_africa_.22less_developed.22.3F .

For a slightly different question, there was a summary answer by jschooltiger in https://www.reddit.com/r/AskHistorians/comments/3ddx46/do_third_world_countriesmass_poverty_come_from/ , meaning that they pointed at a number of different other articles. The two that look more applicable:

• https://www.reddit.com/r/AskHistorians/comments/2c4lni/why_is_colonialism_responsible_for_terrible/ , with too many commenters to single out one.
• https://www.reddit.com/r/AskHistorians/comments/1jax1a/what_was_the_economy_of_africa_like_before_and/ , with several replies by /u/khosikulu.

I'll give this a try. My first answer here, so please bear with me on this. My points are taken from these two books:

Walter Rodney - How Europe Underdeveloped Africa (1972)

Eric Williams - Capitalism & Slavery (1944)

First of all it is important to understand, that both books attracted criticism for their thesis. Some scholars claimed, that both authors were not in a scholastic approach to history, but a political approach. Meaning that they wanted to carry a message. Other criticized them for the methods and data they used. They could be considered outdated by contemporary standards, however they are in my opinion still a worthwhile read.

Other then that one has to remember that "development" can be considered an eurocentric concept. Meaning that development means only the European way of culture, economy and so on and that every kind of development has to follow the European path sooner or later. A lot of African and increasingly Western scholars disagree with that idea. Therefore development is nothing linear, if it's measurable at all. Rodney dedicates his first chapter to this question.

Now to the question at hand:

Rodney argues that the Atlantic slave trade is mainly responsible for the shortcomings of African societies. For this there are several reasons:

1. The slave traders targeted primarily young, able bodied men. Therefore robbing the societies of the most productive and reproductive generation.

2. Slave traders targeted well educated people. Leading to a considerate brain drain in those societies, robbing them of skilled craftsmen and labour. Also this stagnated new innovations.

3. The danger of being enslaved caused people to flee out of their home societies. They stopped advancing their society, but instead concentrated on survival only.

4. The scope of the slave trade meant demographic stagnation on the African continent. While other continents experienced a growth in population throughout the 17-19th century, the population of Africa remained on the same level.

Main points are taken from Rodney's fourth Chapter.

Williams chose a different approach by analyzing the benefits of the triangular slave trade on the British economy. In the chapters 5 & 8 he first talked about how the profits of the slave trade kickstarted the British financial sector and funded innovation like the steam engine. One of the key sectors of the early industrialization was cloth and clothing. Primarily the processing of cotton, imported from the big slave plantations in the Americas.

If you follow Marxist theory he further noted that the profits and resources gained from slave trade advanced the British economy into its next mode of production. Away from mercantilism with its partly feudal roots, to a truly modern form of capitalism. By this the slave trade helped European societies to advance economically and gain a crucial advantage over other parts of the world.