Strange as it may seem, Adam and Eve spoke a primitive version of Appalachian English.
The reason we know this is because in some of the lost chapters of Genesis we find out that Adam and Eve were actually part of a larger tribe of primitive humanoids who had just begun (towards the closing chapters of the classic tale) to do things like wear animal skins, think abstractly, form language, and walk upright.
Since Eve found herself pregnant with twins during this transitional period, and since human anatomy hadn't completely adapted itself to an upright posture yet, the unborn twins, suspended in Eve's womb in a sort of yin-yang position as they were, were receiving nutrients to different parts of their bodies and so, were developing differently: one was receiving nutrition mostly to his lower extremities, the other to his upper developing body, particularly to his head.
At this stage the primary daily concerns of our early ancestors were pretty basic, and they tended to name their children in accordance with these basic concerns, especially in regards to procreation, or more specifically, the act thereof. Sex was a big deal for them.
So, when the one twin was born with a more than adequately developed set of lower equipment, our early ancestors standards being what they were they decided to call the boy "Abel" (spelling was also still in it's infancy).
When, on the other hand, they got a good look at the second newborn and took note of his almost complete lack of lower development, they immediately named him "Cain't".
As the boys grew it became more and more apparent that while Cain't had been been born lacking in one essential area, he'd been more than compensated for it in others: due to having been suspended upside down in Eve's womb during his earliest developmental stages, Cain't had been born with a much (much) larger brain than his twin, or for that matter any of the other members of his tribe.
Because of this, as time went on Cain't became an ingenuously skilled manipulator of the other members of his tribe as well as a highly pervasive orator, innovator, organizer, and eventually, dictator.
This is why human civilization and it's destiny has mostly been in the hands of sexually dysfunctional dictators who were also highly skilled orators and manipulators, ever since.