It also fails to take into account that, until relatively recently, families simply didn't feed their girls as much as they fed the boys.
Girls would cost them money when it came to marriage, either through dowry or merchet. This was especially the case pre-industrialisation for most and post for the poor during the lean months of May to August when the price of food went up. Women "passing on their genes" became moot when they were so malnourished that their menses were stopped.
Even if women were of a weight to be able to bear children, the constant round of underfed pregnancy and dangerous birth meant that few women lived out their fertile years. Those that did often lived to a ripe old age, which meant they were a burden on their families. So, rich ones were packed off to convents and poor ones accused of witchcraft and strangled at various points in history.
However, it's quite difficult to generalise about these things, because there have been different pressures on women's mortality rates over the ages. I'd be quite interested to know when women outnumbered men 2:1 though, because I've never seen anything to suggest that's correct.