So how do you explain glam rock, an entirely male phenomenon? What about Beau Brummell and dandyism?

Or to use a more up-to-date reference, how do you explain this: https://www.shutterstock.com/search/glamorous+men

Why when I do a search for "glamorous men" does google present me with 124 million results?

As for the claim that in gatherer-hunter societies, the prevailing ethos was:

Early woman: Needing to deal mostly with children or other close at hand mundane tasks, early woman had little need for muscle or shows of ability. Rather, early woman needed to look good, in an attempt to capture and hold the attention of the best available early man, indirectly competing with the other woman. To call such a person "glamorous" would be a complement.

Early man: needing to deal mostly with the gathering of food and the defending of family and friends from other tribes. Early man cared little for appearance or complicated thought. Things of pride for early man were: Muscle (for raw power), Hair (a sign of tough skin), and scars (a sign of proven endurance). Those things are not good looking or flashy, so calling a man "glamorous" indicates that they do not poses the qualities of power or resilience. Down to the caveman in all of us, it's taken as an insult.

None of this comports with reality. The bulk of calories in gatherer-hunter societies were provided by women. Women in early human societies weren't weaklings with no muscle who spent their lives sitting around trying to look beautiful and glam the way you and these other poorly-informed sexists allege. And they certainly weren't sidelined by pregnancy, childbearing and childrearing. Though a good number died in childbirth or shortly before or afterwards.

Gestating and giving birth to offspring are actually extremely strenuous activities involving some of the most muscular organs in the human body - the uterus, cervix and vagina, as well as muscles both sexes have like the muscles of the thighs, the groin and and the glutes. Birthing, feeding and "dealing with" children" actually require "a show" of all sorts of abilities. The claims made by you and these other folks you cite could only come from people who've never been pregnant, given birth or reared children - or closely witnessed these processes as adults IRL.

And no one back in the days of "early woman" and "early man" had mirrors, fashion magazines or any concept of "glamour."

Also, evolutionary biologists all say that in primates and early human civilizations, the males are/were the ones who have/had to compete for the attention of females, who are the ones who do the choosing.

In a large number of animal species - from peacocks and other birds to lions - it's the male who are the more "glamorous" ones, and it's the male who engage in a variety of behaviors meant to get the attention of females and convince the females to mate with them. Males are the original "pick me's."