Final answer:
The lowest tactile acuity for two-point discrimination is found on the back and thighs due to less dense distribution of sensory receptors compared to the high tactile acuity in the fingertips.
Step-by-step explanation:
In the context of two-point discrimination, the lowest tactile acuity is typically on areas of the skin where sensory endings and receptive fields are not as densely packed. These regions include the back and thighs, contrasting with high tactile acuity found on the fingertips. This is because the fingertips contain a high concentration of specialized sensory receptors like Merkel's disks and Meissner's corpuscles which are responsible for fine touch and detailed surface texture perception. Conversely, areas like the back and thighs have a wider distribution of single sensory receptors, leading to larger receptive fields and decreased ability to distinguish closely spaced stimuli.