There isn’t really a big difference between the ribs of men and women.
The idea comes from the Old Testament account of the creation of Eve from Adam’s rib.
However, the main sex difference is that women’s ribs are a little smaller on average.
The bones forensic anthropologists really look at, the most reliable ones, are the bones of the pelvis, consisting of three bones: the two hipbones and the sacrum, which make a bony ring.
The difference between males and females is related to the reproductive functions of the pelvis.
In general, female pelvises are somewhat broader and more basin-like, while male pelvises are relatively narrow and somewhat constricted, especially the inner part, where a baby’s head must pass in a woman.
The skull is also helpful but not quite as reliable as the pelvis.
In the male skull, the brow ridges, the bones above the eyes, and the mastoid processes, the lumps of bone behind the ears, are relatively larger.