Human evolutionary adaptation to the environment

Here's an interesting parallel:

When humans started to walk upright, the female pelvis became smaller as a result of bipedalism. As a result, human babies spent less time developing inside its mother and more time developing outside. No other animal species takes so long to mature into adults. In a way the quality of childbirth can be said to have decreased, in order to take advantage of the gains from bipedalism.

Here's the modern parallel: when humans gained control over their reproductive systems (the birth control pill, condoms, etc), the institution of marriage was fairly quickly eroded away. As a result, children faced several developmental difficulties due to the lack of the family framework. In a way, the quality of children can be said to have decreased in order to take advantage of the gains from the control over reproduction.

Now it is no doubt that bipedalism was a good thing. And yet, I can almost imagine a scene during that time (when bipedalism was on the rise) in which the "conservatives" (those against bipedalism) were railing against the "liberals" (who were for bipedalism) because of the harm being caused to the babies.

Contraception was a turning point, on the same scale as bipedalism. Are the conservatives of today needlessly worrying? Will humanity adapt to the new environment? What are the benefits that contraception brings us that is on the same scale as the benefits that bipedalism brought us? If "success" in evolutionary terms means having the most viable offspring, then doesn't it follow that there is evolutionary pressure to not use contraception? 9