Physical Attraction-not the kind between an electron and a proton if ya know what I mean

When I was younger, probably entering puberty, I came to believe that physical beauty, by which I suppose I mean sexual attraction-just to be perfectly clear, was largely a societal construct. Think about it, the Venus de Milo would be "plus size" and even Marilyn Monroe would be a size 12-16, a far cry from today's "supermodels" whose dress size approaches or is the additive and multiplicative identities of the integers/real numbers. I think it's probable that today's nice skinny figures would be considered emaciated skeletons by earlier standards, especially in those societies that valued the ability to reproduce, looking for "hearty women with child bearing hips."
My point here is to ask how much physical attraction is societal, though. Obviously sexual attraction to women, in male's case and vice-a-versa, is natural inborn desire used to perpetuate the race, but I wonder if the specifics are essentially manufactured. If you like women with big breasts, is there anything to that other than a sort of societal brainwashing? To be truly free of being a mindless follower of the crowd, must we throw off the chains of what physical characteristics are sexually attractive and look deeper into people's souls to find our attraction?
People often speak against this idea when I present it, usually with the line, "There has to be some physical attraction in a romantic relationship." Well, I agree (duh) if you find your partner a repulsive specimen of the human form that things are gonna be rough. However, physical attraction is mental, and often changes according to our opinion of someone. One may have heard that confidence is important to looking good, and it's true. Many people have probably experienced a growing attraction to someone as they got to know them better. One slowly overlooks flaws and focuses more on attractive aspects, or vice-a-versa according to one's opinion of another.
I'm sure folk have opinions on this, and I'll be interested to see the discussion that ensues.