Well maybe not 8-9 times stronger but:
"It's already known that males' upper bodies, on average, have 75% more muscle mass and 90% more strength than females'. But it's not known why."
Elk have antlers. Rams have horns. In the animal kingdom, males develop specialized weapons for competition when winning a fight is critical. Humans do too, according to new research. Fighting may have long been a part of our evolutionary history.
www.sciencedaily.com
When you go further down the rabbit hole of sex differences though things get really strange on a lot of measures. Like muscle mass not always equating to strength and figuring out why women tend to outdo men in a lot of endurance based activities. Why lower body strength seems to work differently and on and on. But in terms of muscle mass and upper body strength you're the freaking Hulk compared to any female.
Eventually we'll figure out that there are different mechanisms at play in men and women (muscle mass might be a great measure for men but not a good gauge for women) but for now go carry the groceries in.