The flat earth theory always had opponents. And it was generally accepted among many scholars that the earth was a sphere as far back as 2500 years ago (in Greece) Certainly by the time of the voyage of Columbus, the flat earth idead was essentially dead. But at no time did it ever gain unopposed acceptance.
As a baptist you are an offshot of the protestants, who themselves broke away from the Roman Catholic church.
To make it germane to evolution: Religion like many traits tends to be hereditary, and if you'd been born in Saudi Arabia most likely you'd be muslim. Or Buddhist from Bhutan.