You might definitely want to check out the work of [Eric Williams] (http://en.wikipedia.org/wiki/Eric_Williams) specifically "Capitalism and Slavery." Though its "old" for a history book (1944 first publication), I would say its fair to call it a classic.

The argument he makes is essentially that capitalism- that is economic needs- drove the creation and expansion of the African slave trade and it was only after the fact that a racial rational was given to explain why it wasn't morally wrong for European's to use enslaved African labour on their plantations.

Oddly enough, the argument you are making in your last paragraph would be in favor of slavery being driven by economics rather than race. If we accept that institutionalized forced labour was present in Europe before the slave trade, and Europeans were merely exporting a system that already existed in their own lands to the Americas, but instead of brining over serfs, they used enslaved Africans, then really they are just recreating an economic system that already existed, rather than creating a new one based on race. There is certainly something to this argument; its not surprise that the Spanish or Portuguese for instance will turn to slave labour after their indigenous work force begins dying off from disease.

Personally- I find Williams' argument to still resonate well sixty years later; that capitalism- the need for a cheap labour supply, fueled the growth of slavery and once the institution was up and running, racism gradually evolved as a way to explain why the system wasn't morally bankrupt. Williams further argues, that in fact, it was the slave labour and the profits of the slave trade that really sparked the industrial revolution back in England/Europe. Though this last point is a bit more controversial.

Slavery came first. At first there was indentured servants and slavery in the colonies; native americans and blacks. They would work together to rebel against the whites. When the whites saw what was going on, they introduced different policies for different race of people. The native americans had it easier than the blacks.

What people often seem to mistaken is that racism is encoded in our spectrums and genetics, but this is simply untrue. Children at young age would not make themselves difference from another child of different race unless they were indoctrinated to do so. The idea of racism was introduced after slavery to separate the native americans and blacks from teaming up against the white owners.

The blacks weren't brought over because of their skin color, they were already slaves by the time they were sold to the europeans.

From what I've learned in read about the Atlantic slave trade and slavery in the British Colonies, I'd say that the need for slaves came first and that race was just one factor amongst many that lead to the decision to use slaves from Africa.

Initially, indentured servants from England were used to provide labor in the colonies. Poor English and German men would lease their teenage sons to land owners whom they would work for for a few years and then be set free. Indentured servants became more and more sparse as European average incomes grew, and eventually there wasn't enough available labor to meet the demand in the colonies.

Native Americans were also used as slaves in for a short time, but it was eventually outlawed. Old World diseases destroyed Native populations, and left many of them incapable of providing the type of physical labor that the British and the Colonists needed. On top of that, Native Americans had to be captured before they could be used as slaves, and that was both a dangerous and difficult task. So between the declining Native American population and the difficulties of even capturing them to begin with, Native American slave labor wasn't really a feasible option.

That left the British with only one real option as far as they were concerned, and that was to use African slaves to provide the physical labor needed in the colonies. Obviously, the use of African slave labor proved to be very effective and profitable for the British, the Colonists, and later the Americans. African slaves were widely available for purchase from West African tribes who would sell the people that they captured in battle to the Europeans. On top of that, African slaves had better natural immunities to Old World diseases unlike the Native Americans, so mortality rates for things like smallpox were much lower. Now, as I said before, ethnicity and skin color did factor into the decision to use African Slaves instead of Native Americans or poor Europeans. Africans were considered to be less like Christians than the Native Americans were because of their darker complexion. Therefore, it was said to be more acceptable to use the Africans as slaves than the Native Americans. To me, this just seems like a way to justify owning another human being though, and not a reason for using slave labor. The economic gains were reason enough for slavery to be attractive to the British and the Colonists.

Something to consider is that slavery is very old in the west: it didn't spring just from feudalism or other top-down governments. Slavery dates at least to the early Roman republic, where captives from vanquished armies and territories could be enslaved. (For later examples, e.g., Caesar enslaved the residents of a town that surrendered to him, but then rebelled; Augustus limited the right to testamentary manumission.) If you go to the Met Museum, or indeed any major ancient museum, you'll find metal plates testifying to slave contracts.

The distinction you need to draw is between slavery, and race-based slavery.