Those were flanked by the salt-detecting buds, with the sour ones running farther along the sides. The bitter buds, last defense against gag-inducing toxins, lurked across the back of the tongue. Nice, neat, orderly. And not very accurate. There are taste buds throughout the oral cavity, even on the upper palate.
Any bud is capable of detecting all the basic tastes.
It's just that some are more sensitive to a particular taste than to the others. The tongue map also neglects to take into account the impact the other senses have on taste. In a lot of cases, you pick up clues about the food you're about to eat long before any of it gets into your mouth. Like that left-over beef stoganoff that's been sitting at the back of your refrigerator for a month. Chances are, you won't even bother to dirty a fork before chucking that rank mess into the Dispos-All.