I merely mentioned this article because it is a common fear among some women that heavy lifting causes excess muscle-gain. Come to think of it, the personal trainers I have occasionally used, also recommended that I use higher reps and lower weights(I suspect that they just wanted me to take more lessons in order to achieve results re bigger muscles etc.!).
They are trying to prevent you from getting injured. Most injuries during weightlifting happen because of using too much weight. There's very little that a 1 to 3 reps per set routine will accomplish that a 10 to 20 reps one won't, in terms of muscle gains, but there is a lot the first can accomplish that the second is much less likely to, in terms of injuries.
The point being that, in Palaeolithic times, women were likely far more subject to increased exercise due to daily activity than nowadays,
Doubtful. It was the men that hunted and engaged in battles with other tribes, and who fought off non-human predators. And some research suggests that even those men were much less physically active than most fitness enthusiasts today.
and reduced fertility, in those days, would have been more of a blessing of sorts as a matter of survival(note the mass infanticide prevalent in Palaeolithic times, for example). The only other effective contraception, in those days, was breastfeeding.
You're still misunderstanding this. Infanticide was for the benefit of the tribe's genes, not for the benefit of the woman's genes. It was in her benefit to have as many babies as possible in order to have as many of them survive and reproduce as possible. Especially when the raising and resource pooling would take place at a tribal level, and so her own contribution to her child's upbringing would be comparatively minimal.
There is, of course, nothing wrong with women gaining muscle-mass. I recall a study, I forget where, wherein men in their 70s and 80s were forced to lift weights and train like they did when they were 40. They experienced similiar muscle-mass gain in the end to what they had in their 40s and improved overall. The point being that increased aging has been linked to reduced muscle-mass in the elderly. Plus, reduced muscle-mass can lead to an increased chance of falling in the elderly etc.
There's a reason why it took incredible levels of media propaganda in order to make men believe that women with six-pack abs and weightlifting arms were attractive. For the vast majority of human history, they were not considered attractive.
Also, selection bias. People who are healthier will have stronger muscles and more of an ability and drive to engage in activities that include exercise. That does not necessarily mean that you can take someone who is unhealthy, force them to exercise against their will, and that this will improve their health. Chances are, it will do the opposite.