Hi, this is an extract from a chapter from an evolutionary psychology book on dating titled 'youth' in section "What Men Want" of "The Evolution of Desire: Strategies of Human Mating" by David M. Buss, can you summarise this section?

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Youth
It is a fact of fertility that women’s reproductive capacity declines steadily
with increasing age after the midtwenties. By the age of forty, a woman’s
reproductive capacity is low. By fifty, it is close to zero. Women’s capacity
for reproduction is compressed into a fraction of their lives.
Men’s preferences capitalize on this critical cue. In the United States,
men uniformly express a desire for mates who are younger than they are.
Among college students surveyed from 1939 through 2005 on campuses
coast to coast, the preferred age difference hovered around two and a half
years.5 Twenty-one-year-old men preferred, on average, women who were
eighteen and a half.
Men’s preoccupation with a woman’s youth is not limited to Western
cultures. When the anthropologist Napoleon Chagnon was asked which
females are most sexually attractive to Yanomamö men of the Amazon, he
replied without hesitation, “Females who are moko dude.”6 The word
moko, when used with respect to fruit, means that the fruit is harvestable,
and when used with respect to a woman, it means that the woman is
fertile. Thus, fruit that is moko dude is perfectly ripe, and a woman who is
moko dude is postpubescent but has not yet borne her first child, or about
fifteen to eighteen years of age. Comparative information on other tribal
and traditional peoples suggests that the Yanomamö men are typical in
their preference.
Nigerian, Indonesian, Iranian, and Indian men are similarly inclined.
Without exception, in every one of the thirty-seven societies examined in
the international study, men preferred wives who were younger than
themselves. Nigerian men who were twenty-three and a half years old, for
example, preferred wives who were six and a half years younger, or just
over seventeen years old. Croatian men who were twenty-one and a half
years old expressed a desire for wives who were approximately nineteen.
Chinese, Canadian, and Colombian men shared with their Nigerian and
Croatian brethren a powerful desire for younger women. On average, men
from the thirty-seven cultures expressed a desire for wives approximately
two and a half years younger than themselves.
Although men universally preferred younger women as wives, the
strength of this preference varied somewhat from culture to culture.
Scandinavian men in Finland, Sweden, and Norway preferred their brides
to be only one or two years younger. Men in Nigeria and Zambia preferred
their brides to be six and a half and seven and a half years younger,
respectively. In Nigeria and Zambia, which practice polygyny, like many
cultures worldwide, men who can afford it are legally permitted to marry
more than one woman. Men in polygynous mating systems are typically
older than men in monogamous systems by the time they have acquired
sufficient resources to attract wives. The larger age difference preferred by
Nigerian and Zambian men probably reflects their greater age when they
acquire wives.7
This interpretation is supported by a raft of scientific studies showing
that, as men get older, they prefer as mates women who are increasingly
younger than they are. Consider the statistics derived from online personal
advertisements.8 A man’s age has a strong effect on his preferences: men
in their thirties prefer women who are roughly five years younger,
whereas men in their fifties prefer women ten to twenty years younger.9
Although these findings support the evolutionary hypothesis that men
prefer younger, and hence more fertile, women, this perspective actually
leads to a very counterintuitive prediction—namely, that young adolescent
males should prefer women who are slightly older than they are. Scientific
studies bear this prediction out. Adolescent males age fifteen, for example,
express a desire for females who are seventeen or eighteen.10 What is
fascinating is that this attraction is almost entirely unreciprocated. Women
in their late teens do not even notice these young adolescent males, much
less find themselves attracted to them. They prefer men a few years older,
not a few years younger.
These findings regarding adolescent males contradict two potential
alternative explanations for why older men are attracted to younger
women. One—an old standby in psychology—is reinforcement theory: that
people repeat behaviors for which they are rewarded. Adolescent males
are hardly reinforced or rewarded by the women they are most attracted
to; indeed, they are ignored or actively shunned by these women. A
second explanation is that men are attracted to younger women as a
means of exercising power and control. But the mid-adolescent males have
no power or control at all over the late-adolescent women they find so
beautiful. The fertility explanation, in short, provides the most compelling
explanation for the entire pattern of findings, from the attractions of
adolescent males to men’s attractions toward women who are increasingly
younger relative to their own age as the men get increasingly older.
Actual marriage decisions confirm the preference of men for women
who are increasingly younger than they are as they age. American grooms
exceed their brides in age by roughly three years at first marriage, five
years at second marriage, and eight years at third marriage.11 Men’s
preference for younger women also translates into actual marriage
decisions worldwide. In Sweden during the 1800s, for example, church
documents reveal that men who remarried following a divorce selected
new brides 10.6 years younger on average. In all countries around the
world where information is available on the ages of brides and grooms,
men on average exceed their brides in age.12 Among European countries,
the age difference ranges from about two years in Poland to roughly five
years in Greece. Averaged across all countries, grooms are three years
older than their brides, or roughly the difference expressly desired by men
worldwide. In polygynous cultures, the age difference runs even larger.
Among the Tiwi of northern Australia, for example, high-status older men
often have wives who are two and three decades younger than they are.13
In summary, contemporary men prefer young women because they have
inherited from their male ancestors an evolved preference that focused
intensely on this cue to a woman’s reproductive value. This psychological
preference translates into actual mating decisions much of the time—
although as we will see later, people can’t always get what they want.
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