Final answer:
The lowest tactile acuity is on regions with lesser sensory receptor density, such as the back and thighs, as opposed to areas with high receptor density like the fingertips and lips.
Step-by-step explanation:
In the context of two-point discrimination, the lowest tactile acuity, meaning the areas with the least sensitivity to fine touch, are typically on regions such as the back and the thigh. These areas have larger receptive fields due to a lower density of sensory receptors and thereby require a greater distance between two points to be perceived as separate stimuli. In comparison, areas like the fingertips and the lips have higher tactile acuity with denser concentrations of sensory receptors like Merkel's disks and Meissner's corpuscles, allowing for finer discrimination of touch.