Because of evolution and natural selection in our tribal past, the men who were fiercely tribal, killing the men of other tribes and taking their women, were genetically successful, thus rewarding tribalism. Conversely if you were a woman and your tribe was conquered by another and all the men of your tribe was slaughtered, those women who showed tribal loyalty would be much less successful at passing on their genes than those who didnt care about tribes and just wanted to love everybody. Thus explaining the data from psychology which shows men are predisposed to a heavy racial in-group preference while women instead show a heavy gender in-group preference. This much seems logical and straitforward. Karen Straughan was the first I saw advance this theory and I believe Gad Saad has spoken in support of it as well.
Many however have extrapolated this with the observation that the counter-culture movement was directly proceeded by great strides by the feminist movement. For those who dont know, feminism started in the mid-1800s, was firmly rejected until the interwar years when it started to gain traction(because of female workers during the state of total war in WW1) and rapidly accelerated after WW2 becoming much more popular in the late 40s and 50s. Well I don't know how true this is in America or Europe, but in Canada it is seemingly demonstrable. Enter Ellen Fairclough:

She was the first Canadian female MP. She won her local election in 1950, and was a vocal supporter of feminism in the Canadian parliament. When John Deifenbaker won the federal election in 1957, he appointed her secretary of state, and the following year she became minister of citizenship and immigration. She held the office for 6 years until 1963, during which she eliminated many of the traditional ethnic/racial restrictions practiced in Canadian immigration, also increasing the number of immigrants allowed per annum and allowing more refugees. While Canada did not adopt the political identity of multiculturalism until Pierre Trudeau's government in 1971, Canada had indeed already entered a state of purely civic nationalism by the will of its first female MP a decade earlier.
