What is meant here by "pure" endurance?In terms of pure endurance there seems little (if any) difference between men and women though, so I don't see why women's races aren't longer (that they are slower than the men and would take longer to finish isn't a strong argument imo; you don't necessarily have to televise it all).
17 y.o. boys run marathons faster than women. There's a stark athletic difference between men and women in pretty much all dimensions.