Women were given the right to vote in the USA in 1920. Calvin Coolidge (1872-1933) was the 30th President of the United States from 1923-1929. In the year in which he took office Henry Ford perfected the assembly line and a model T Ford could be built in 93 minutes and purchased for $295.00. People were becoming better educated. Increasing literacy led to more newspapers, tabloids, and more advertising being sold. Media moguls such as H. Randolph Hearst were constructing their empires of film, radio, newspapers, and magazines.

After the trauma, bereavement and depression which followed on the ending of World War I the 1920s were a decade of fun and excitement. It was the era of Clara Bow, the rags to riches "It" girl, who became a star of the silent screen. It was the Roaring Twenties and a time of parties, gangsters, Prohibition, the flapper and dancing the Charleston. 'Flapper' was a somewhat derogatory term referring to a very fashionable style among young women, allegedly modeled to some extent on the look of French prostitutes who had comforted American doughboys during the war.

The style was characterized by short hair, tight-fitting cloche hats or berets, and short skirts, often with long fringes so the skirts seemed longer, which enabled the young women to do the side-kicks from the knees required by the Charleston. Flapper was not a term which signified intelligence but rather dizzy empty headedness.

The American Birth Control league was formed in 1921 by Margaret Sanger and Mary Ware. Safe and reliable contraception was finally becoming available. The standard of living was increasing as were consumerism and advertising. All of which provided work. The cosmetics industry began to boom and advertising began to more intensively promote beauty, youth and thinness as ideals.

Now, as legend has it, in the midst of this decade of excitement and development, one day President Coolidge and his wife were visiting a chicken farm. While President Coolidge was inspecting another part of the farm the farmer was showing Mrs. Coolidge a rooster which, she was told, could copulate with a hen all day every day. "Tell that to the President," she said to the farmer. Dutifully the farmer told President Coolidge about the rooster's prowess and how it could copulate all day long. "With the same hen?" asked President Coolidge. "No sir," replied the farmer. "Tell that to Mrs. Coolidge", said the President.

This phenomena, that males of most species are generally more sexually excited by sexual novelty than females, is known as the Coolidge effect. A variety of experiments have been conducted with different species and the findings are robust. For example, if a male rat is put in a cage with a female rat there will often be an initial frenzy of copulation but after a while the male rat loses interest and it is very difficult to persuade it to copulate with the female. However, if a different female is put in the cage there is a renewed frenzy of copulation. This process can be repeated until the rat practically dies of exhaustion. Now, before any readers who are anti-male get excited at the thought that I am saying that men are rats I wish it to be clear that I am not saying all men are rats though some undoubtedly are. Nor am I saying that this tendency in men is morally "right" but rather it is important that we understand in the interests of greater sexual harmony how the different attitudes of the sexes towards sex evolved. Men also are much more given to homicide the world over than women and this is also part of their "nature" which clearly needs to be civilized in the interests of a humane society. Human psychological sexual preferences evolved over hundreds of thousands of years in a hunter-gatherer lifestyle before there was safe and reliable contraception and in which there was considerable risk of morbidity in childbirth for the woman and high infant mortality rates. These preferences "made sense" then and helped the human race to survive. They may not make sense now but, as they evolved over hundreds of thousands of years, we may not be able to change them overnight.

The greater cost in terms of an expenditure of both physical and emotional energy, as every woman who has been pregnant knows, is to the mother even though offspring will on average have 50% of the mother's genes and 50% of the father's. It is thought that the Coolidge effect evolved because the best way for the genes of the males of mammalian species to pass themselves on is for them to impregnate as many females of the species as possible. The probability is that some will survive. Therefore at the dawn of humanity, as we slowly evolved from our primate ancestors, those men who impregnated more females were more likely to pass on their genes to offspring which survived than those that did not.

However, to allow this to happen is not in the best interest of the woman and her offspring. Life in these times can be tough enough-never mind living in the Stone Age which was populated with great beasts and other forms of hominid such as the Neanderthal. Any sensible woman would want some indication that a man was going to show commitment to her and her offspring before allowing him access to her valuable reproductive resources. Those women who were careful in this way and chose higher status men with access to resources were more likely to have offspring that survived than those that did not.

A man would not want to put this kind of investment of energy and risk (a little imagination is all that is needed to realize that hunting mammoths and other great beasts was very risky business) into a woman who was not healthy and whose offspring, carrying 50% of his genes, might not survive. Physical beauty is intrinsically linked with health, youth and fertility at least in pre-technological societies. The biological purpose of beauty is to attract for purposes of sex. The biological purpose of sex is reproduction. Beauty in women evolved in order to attract and hold the interest of men.

The standards of what is beautiful might vary from culture to culture and from epoch to epoch but there is something within female psychology which leads women to want to be beautiful and attractive to men. Women want to be beautiful because to be beautiful is to be desired by men and this means, hopefully, having access to a man's resources for herself and her offspring in order to ensure their survival. Throughout cultures world wide women's looks are more important to men then a man's looks are to women. While a man's looks might be important to women, when it comes to a long-term partner women are more interested in a man's access to economic resources (or prowess in hunting or fighting in less developed societies). There is no culture in which women actively seek to be unattractive to men and any culture in which that has been the case has not managed to reproduce itself. It is important to realize that this evolved over hundreds of thousands of years in environmental circumstances very different from our own.

There are many different reasons why fashion is such a powerful cultural and economic influence in developed societies at the beginning of the 21st century and why it has been so powerful during the twentieth century. The economic interests of manufacturers and advertisers has certainly been important but it is highly unlikely that these would have been successful unless their message met a receptive audience within the mind of the culture.

Just as men compete with one another so do women. Women want to stand out and be noticed. To wear something beautiful, if not outrageous, does just this. It gives a woman a competitive advantage with regard to other women. The most brightly coloured and scented flowers in the otherwise verdant green of a tropical jungle tend to attract the most visits from potential insect pollinators. How many women, when they ask another woman what she is wearing to a function, do so because they want to make sure they are wearing the same thing? To be fashionable is also an indication of status because, initially in any case, designer wear is expensive and beyond the reach of most. It indicates status, power, and access to resources. Fashion, initially outrageous, is then copied by other women so that by definition it becomes less outrageous and more the norm. The boundary keeps moving further back so that the outrageous has to become even more extreme.

However, equally important is to wear something "new." Women do not like to always look the same. This, for many of them, is boring and a psychological preference which probably evolved in response to the Coolidge effect in men. To wear something different, to have a different make-up, a different style is to bring an element of "newness" into the equation and to appeal to men's (or her man's) innate desire for novelty. Of course, the risk in the new look or the new hairstyle is that it will not be found to be attractive, hence the significant anxiety which women often find themselves experiencing when they make such a change.