If you put a spotlight into the scene, it probably defaulted to being a point light. (
mgomez0077 is correct that lighting can be to blame). If you change the light to be a rectangle, you won't get the kind of impossibly hard edges that point lights cast. (No REAL light is a true point.)
However, the real culprit here is light that just "grazes" a model. Real people have smooth contours. Daz models only approximate that - the figures are made up of a whole bunch of quads. (This becomes more obvious if you shift your viewport to one of the modes that has "Wire" in it - it shows outlines around each quad.) What you're seeing on her bottom are the quads that actually make up the model - because of the angle the light is hitting her, you're able to see (there) that she's made up of facets, as opposed to a perfectly smooth contour. A larger light (rectangle not point, or else a larger rectangle) will reduce this effect.
The other option is to have the model be made up of smaller facets so that it more closely approximates a smooth surface. One of the settings available on most Daz figures is the "sub-division level." It's located under "General > Mesh Resolution".
Each time you bump a subdivision level up by one, Daz will take all the quads in the model and break them into four smaller quads. So if you raise the number by 1, you get 4x the amount, if you raise it by 2 you get 16x, etc. This can help in situations like this. It comes at a cost, however - this will increase the amount of memory that the mesh takes up. With most models, the size of the textures is a much bigger factor than the size of the mesh, but if you go hog-wild on the subdivision level, you
can blow yourself out of the water memory-wise.
Daz has separate settings for the viewport ("SubDivision Level") and when you actually render ("Render SubD Level") The default settings for the model I'm showing above uses 3 for viewport (64x the base mesh) and 4 for renders (256x the base mesh). These are pretty typical settings. So, if lighting doesn't fix it, you could try kicking the "Render SubD Level" up by one or two and see what that does for you.
