Dr. Seers is close.
A “social construct”–in the context of groups of people–is just a stereotype. We’ll call it an “idealized version.” We learn this idealized version by interacting with many individual instances of a particular type of thing and learning to predict its typical behaviors and characteristics.
Suppose I asked you to draw a picture of a man and woman. Go ahead, if you want; then you can compare it to the draw-a-man test.
Out in reality, there are about 7 billion men and women; there is no way you drew someone who looks like all of them. Chances are you drew the man somewhat taller than the woman, even though in reality, there are millions of men and women who are the same height. You might have even drawn hair on the figures–long hair for the woman, short for the man–and some typical clothing, even though you know there are many men with long hair and women with short.
In other words, you drew an idealized version of the pair in order to make it clear to someone else what, exactly, you were drawing.
Our idealized pictures work because they are true on average. The average woman is shorter than the average man, so we draw the woman shorter than the man–even though we know perfectly well that short men exist.
Once an ideal exists, people (it seems) start using artificial means to try to achieve it (like wearing makeup,) which shifts the average, which in turn prompts people to take more extreme measures to meet that ideal.
This may lead to run-away beauty or masculinity trends that look completely absurd from the outside, like foot binding, adult circumcision rituals, or peacocks’ tails. Or breasts–goodness knows why we have them while not nursing.
Our idealized images work less well for people far from the average, or who don’t want to do the activities society has determined are necessary to meet the ideal.
Here’s an interesting survey of whether people (in this case, whites) consider themselves masculine or feminine, broken down by political orientation.
The same trend holds for women–conservative women are much more likely to consider themselves to be very feminine than liberal women. Of course, ideology has an effect on people’s views, but the opposite is probably also true–people who don’t feel like they meet gender ideals are more likely to think those ideals are problematic, while people who do meet them are more likely to think they are perfectly sensible.
And this sort of thinking applies to all sorts of groups–not just men and women. Conservatives probably see themselves as better encapsulating the ideal of their race, religion, nationality (not just American conservatives, but conservatives of all stripes,) while liberals are probably more likely to see themselves as further from these ideals. The chief exceptions are groups where membership is already pre-determined as liberal, like vegetarians.
This may also account for the tendency people have, especially of late, to fight over certain representations. An idealized representation of “Americans” may default to white, since whites are still the majority in this country, but our growing population of non-whites would also like to be represented. This leads to pushback against what would be otherwise uncontroversial depictions (and the people who fit the ideal are not likely to appreciate someone else trying to change it on them.)