The most common injuries were fractures of ribs, spines, pelvises, and lower extremities. Other primates have straighter and wider pelvises compared to humans. Women whose pelvises were deemed too small received caesarean sections instead of birthing naturally. Sexual movement is focused in the pelvises, without leverage from the arms or legs. Additionally, female pelvises widen during puberty through the influence of sex hormones. Earlier arguments for a sprawling stance include deep pelvises and features of the legs. The crew returns to Earth where Fry and Zapp receive treatment for their crushed pelvises. The twins' two pelvises formed a single combined ring.