Did the Trans-atlantic trade have more of a positive or negative effect on world history?
The net effect of the trans-Atlantic trade was positive, although it had rather severe negative effects also. This trade gave rise to the Atlantic World, a steady stream of commerce between Europe and the Americas. Among its benefits, useful plants and animals which were exchanged between the two continents. Europe was probably the greater beneficiary with the introduction of corn (maize) and potatoes which substantially improved the average European diet. Gold and silver from the Americas also flowed to Europe, not always with good effects. A substantial influx of gold to Spain in the sixteenth century ruined the Spanish economy.
Among the negative effects were the transmission of diseases between the continents: smallpox, chickenpox, mumps and measles to the Americas, syphilis to Europe. Then too, a substantial portion of the trade for many years was the trade in human beings: those brought to the Americas against their will to be used as forced labor and chattel slavery.