In Europe at least, the sexes have different histories. From Galway to Prague women are much the same, but men are not, writes Prof SteveJones
Type the term "masculinity" into Amazon.com (not at first sight the most obvious source) and a thousand titles emerge. A quarter are by women. Some are bilious (If Men could Talk, Here's what They'd Say). Others range from beastly (Men and Other Reptiles) to botanical (Why Cucumbers are Better than Men), while a few - like The Penis Book: An Owner's Manual by Margaret Gore - are simply baffling.
The study of human evolution and of the difference between the sexes began in 1871 with Charles Darwin's The Descent of Man, and Selection in Relation to Sex. It put paid to the myth of Eden, soon seen by most people as no more than a metaphor for the loss of innocence. In the past 10 years (and in spite of the efforts of Margaret Gore) we have gained a new insight into the world of maleness - and who the real Adam and Eve may have been. As the last universal male and female ancestors of us all, they certainly existed (albeit as anonymous men and women surrounded by others whose heritage has not survived).
What does it mean to be male rather than female, Adam rather than Eve? To fans of David Attenborough males are the big, angry and decorative ones, their lives defined by a fight over females. Darwin was happy to apply his theory to ourselves: "Thus man has ultimately become superior to woman. It is, indeed, fortunate that the law of equal transmission of characters to both sexes prevails with mammals; otherwise it is probable that man would have become as superior in mental endowment to woman, as the peacock is in ornamental plumage to the peahen."
That idea has not lasted too well, but whatever their mental powers, males do put a lot of effort into sex and some individuals do much better than others. Thus, only one male sea elephant in 20 has any offspring at all, while most females have at least one pup. Tough though life may be for male sea elephants, in some creatures males are minute. In certain angler fish, for example, they are reduced to a sack of guts and genitals attached to a female backside (and, some might say, what more could any male want?).
If size does not matter, genes might. The Y chromosome defines manhood. The structure is feeble indeed, with just one fiftieth of the 3300 million DNA letters in the entire human sequence. It does bear one crucial structure. SRY, the key to manhood, contains fewer than a thousand DNA bases and acts - rather like the points outside a railway station - as a switch which directs the embryonic locomotive towards one destination rather than the other.
Man's manual has been read from end to end, and its message is oddly depressing. The chromosome unique to men is a microscopic metaphor of those who bear it; the most decayed, redundant and parasitic of the lot, filled with useless DNA and the rusting hulks of broken genes.
But even that does not define maleness, for plenty of creatures manage without Y chromosomes. A marine snail that rejoices in the name Crepidula fornicata forms submarine chains in which the first animal is female, the second male, and so on, with sex turning only on position.
In fact, the only true definition of Adam - to whatever species he might belong - is simple enough: he makes smaller and more abundant sex cells than does his partner. For ourselves, the figures are stark. Men copulate about 50 billion times a year, which comes to around a million litres of semen a day (that may sound a lot, but is a flow no greater than the fledgling Liffey a few miles from its source). Every second, in return for their 200,000 billion global sperm, they are rewarded with five births. The world's women contribute a mere 400 eggs with each tick of the clock for the same result.
Males began as parasites. They use female flesh to copy own genes. In some ancient and neutral Eden, the fruit of the tree of sexual knowledge - a new mutation - persuaded members of a particular clone to fuse with cells from another, and then to divide. That was good news for the novel gene, but less so for those who receive it, who are obliged to copy the extra DNA. At once, two factions emerge, one keen to force itself upon the other. Soon, one player began to cheat. Small cells are cheap to make, but too small to divide without help. Their only chance lies in fusion. The first males had appeared on the scene.
Eggs, in contrast, are packed with the goods needed by the embryo. They bear small structures - mitochondria - which have genes of their own and are inherited only through the female line (sons receive them, but do not pass them on).
Mitochondria trace the descent of Eve, as the Y does that of Adam. They show that in Europe at least, the sexes have different histories. From Galway to Prague women are much the same, but men are not.
The patterns of the Y chromosome can show striking changes over a few miles; and - although in many ways the two nations are indistinguishable - those of most Irish men are quite distinct from their equivalents in England. The Y chromosomes of Wales (and as a Welshman, I have checked my own) look almost like those across the Irish Sea. However, beneath the Caledonian kilt beats many an English Y as many Scots share a heritage with their Saxon neighbours.
MEN like to believe that they have more sexual partners on average than do women. That is, of course, impossible: for it takes two to tango and the average number of encounters must be the same for each sex (which does not stop us from lying, with the average 40-year old Brit claiming 9.9 conquests and his female equivalent only 3.4).
Even so - and just like sea-elephants - there is much more variation in success among men than among women, with a few Lotharios and a large number of unwilling celibates.
That helps to explain the geography of the Y, with the efforts of particularly strenuous men echoing down the generations.
It is also the key to the mystery of Eden.
According to Engels, the beginning of farming 10,000 years ago marked the "world historical defeat of the female sex".
Poor as a peasant might be, his wife was even poorer. She owned too few resources to make any kind of life of her own. Soon, great landowners forced submission (sex included) on to their inferiors.
The evidence for the sordid habits of the powerful lies in the DNA. All Black Americans have some influx of European genes; but only one in 20 of their mitochondria is of European type, while a quarter of their Y chromosomes came from that continent; evidence of rich white Adams forcing their attentions upon poor black Eves.
According to The Guinness Book of World Records, the gold medallist in the genital stakes is one Moulay Ismail the Cruel of Morocco, an 18th century potentate who slew 30,000 Christians with his own hand. Busy though he was, he found time to have 888 children, half of them sons.
For his boys, of course, he was the universal Adam, for every one bore a copy of Moulay's Y chromosome. There were, needless to say, many Mrs Moulay-Ismails - perhaps a hundred or more.
As a result, those sons (and their sisters) inherited a miscellany of mitochondria - and even if all his wives were relatives, as they might well have been, they would have to go back several generations to find their universal shared great-grandmother, the Eve of the Ismaili court.
In a less dramatic way, the same is true of every human pedigree; the tendency for a few men to dominate in the reproductive race while most women have roughly the same number of children means that it takes fewer generations to get back to the universal male ancestor than to the female one. Those mythic general grandparents certainly lived at different times.
Genetics makes one thing clear; that whoever uttered that famous phrase "Madam, I'm Adam" did not say it to Eve.