From 510 to 180 million years ago, South America and Africa were fused together in a supercontinent called Gondwana.
After that time, rifts in the Earth’s crust broke Gondwana apart, separating the Americas from Africa and resulting in the formation of the Atlantic Ocean. However, Christian Heine and Sascha Brune of the University of Sydney and the German Research Centre for Geosciences found that such an eventuality was far from certain. Instead, Africa itself could have split apart with the western half remaining attached to South America. You can see a model of what that might have looked like below.
Credit: Sascha Brune/Christian Heine
For a while (some 20 million years), it looked like either scenario could have played out. Gondwana could have been split between Africa and South America or between Eastern and Western Africa.
Obviously, the former rift proved more powerful and the African rift was eventually abandoned. Thus we ended up with the Earth we have today.