... an analysis that puts the final link in the chain, for here we see correlations between cytological evidence and genetic results that are so strong and obvious that their validity cannot be denied. This paper has been called a landmark in experimental genetics. It is more than that—it is a cornerstone.
Describing the paper 'A Correlation of Cytological and Genetic Crossings-over in Zea mays' published by Barbara McClintock and her student Harriet Creighton in the Proceedings of the National Academy of Sciences (1931), demonstrating that the exchange of genetic information that occurs during the production of sex cells is accompanied by an exchange of chromosomal material.

… however useful the words may have been in the past, they have now become handicaps to the further development of knowledge. Words like botany and zoology imply that plants and animals are quite different things. … But the differences rapidly become blurred when we start looking at the world through a microscope. … The similarities between plants and animals became more important than their differences with the discoveries that both were built up of cells, had sexual reproduction,… nutrition and respiration … and with the development of evolutionary theory.

...philosophy is to science as pornography is to sex.

“Auto erotism,” … spontaneous solitary sexual phenomena of which genital excitement during sleep may be said to be the type.

[I]magine you want to know the sex of your unborn child. There are several approaches. You could, for example, do what the late film star ... Cary Grant did before he was an actor: In a carnival or fair or consulting room, you suspend a watch or a plumb bob above the abdomen of the expectant mother; if it swings left-right it's a boy, and if it swings forward-back it's a girl. The method works one time in two. Of course he was out of there before the baby was born, so he never heard from customers who complained he got it wrong. ... But if you really want to know, then you go to amniocentesis, or to sonograms; and there your chance of being right is 99 out of 100. ... If you really want to know, you go to science.

Mathematical truth has validity independent of place, personality, or human authority. Mathematical relations are not established, nor can they be abrogated, by edict. The multiplication table is international and permanent, not a matter of convention nor of relying upon authority of state or church. The value of π is not amenable to human caprice. The finding of a mathematical theorem may have been a highly romantic episode in the personal life of the discoverer, but it cannot be expected of itself to reveal the race, sex, or temperament of this discoverer. With modern means of widespread communication even mathematical notation tends to be international despite all nationalistic tendencies in the use of words or of type.

Meine Herren, der Senat ist doch keine Badeanstalt.
The faculty is not a pool changing room.
Indignant reply to the blatent sex discrimination expressed in a colleague’s opposition when Hilbert proposed appointing Emmy Noether as the first woman professor at their university.

Nature and nurture are an inseparable blend of influences that work together to produce our behavior. A growing band of researchers are demonstrating that the bedrock of behaviors that make up the concerns of everyday life, such as sex, language, cooperation, and violence have been carved out by evolution over the eons, and this Stone Age legacy continues to influence modern life today.

Almighty God, to whose efficacious Word all things owe their original, abounding in his own glorious Essence with infinite goodness and fecundity, did in the beginning Create Man after his own likeness, Male and Female, created he them; the true distinction of which Sexes, consists merely in the different site of those parts of the body, wherein Generation necessarily requires a Diversity: for both Male and Female he impartially endued with the same, and altogether indifferent form of Soul, the Woman being possess’d of no less excellent Faculties of Mind, Reason, and Speech, than the Man, and equally with him aspiring to those Regions of Bliss and Glory, where there shall be no exception of Sex.

Amazing that the human race has taken enough time out from thinking about food or sex to create the arts and sciences.

Amoebas at the start Were not complex; They tore themselves apart And started Sex.

Among all types of sexual activity, masturbation is ... the one in which the female most frequently reaches orgasm.

An epidemiologist is a doctor broken down by age and sex.

And as I had my father’s kind of mind—which was also his mother’s—I learned that the mind is not sex-typed.

As the first monogamian family has improved greatly since the commencement of civilization, and very sensibly in our times, it is at least supposable that it is capable of still further improvement until the equality of the sexes is attained.

Being the inventor of sex would seem to be a sufficient distinction for a creature just barely large enough to be seen by the naked eye.
[Comment about Volvox, a freshwater green algae, which appears indetermimately plantlike and animal-like during its reproductive cycle.]

By the worldly standards of public life, all scholars in their work are of course oddly virtuous. They do not make wild claims, they do not cheat, they do not try to persuade at any cost, they appeal neither to prejudice nor to authority, they are often frank about their ignorance, their disputes are fairly decorous, they do not confuse what is being argued with race, politics, sex or age, they listen patiently to the young and to the old who both know everything. These are the general virtues of scholarship, and they are peculiarly the virtues of science.

Courtship, properly understood, is the process whereby both the male and the female are brought into that state of sexual tumescence which is a more or less necessary condition for sexual intercourse. The play of courtship cannot, therefore, be considered to be definitely brought to an end by the ceremony of marriage; it may more properly be regarded as the natural preliminary to every act of coitus.

Every animal is sad after coitus except the human female and the rooster.

Every theory of love, from Plato down, teaches that each individual loves in the other sex what he lacks in himself.

FEMALE, n. One of the opposing, or unfair, sex.

Few males achieve any real freedom in their sexual relations even with their wives. Few males realise how badly inhibited they are on these matters.

How twins are born my discourse will explain thus. The cause is chiefly the nature of the womb in woman. For if it has grown equally on either side of its mouth, and if it opens equally, and also dries equally after menstruation, it can give nourishment, if it conceive the secretion of the man so that it immediately divides into both parts of the womb equally. Now if the seed secreted from both parents be abundant and strong, it can grow in both places, as it masters the nourishment that reaches it. In all other cases twins are not formed. Now when the secretion from both parents is male, of necessity boys are begotten in both places; but when from both it is female, girls are begotten. But when one secretion is female and the other male, whichever masters the other gives the embryo its sex. Twins are like one another for the following reasons. First, the places are alike in which they grow; then they were secreted together; then they grow by the same nourishment, and at birth they reach together the light of day.

I conclude that the musical notes and rhythms were first acquired by the male or female progenitors of mankind for the sake of charming the opposite sex.

I have sold more books on physics than Madonna has on sex.
[Hawking adopted this statement from a remark made to him by his former post-doc, Nathan Myhrvold.]

I regard sex as the central problem of life. And now that the problem of religion has practically been settled, and that the problem of labor has at least been placed on a practical foundation, the question of sex—with the racial questions that rest on it—stands before the coming generations as the chief problem for solution. Sex lies at the root of life, and we can never learn to reverence life until we know how to understand sex.

I should like to compare this rearrangement which the proteins undergo in the animal or vegetable organism to the making up of a railroad train. In their passage through the body parts of the whole may be left behind, and here and there new parts added on. In order to understand fully the change we must remember that the proteins are composed of Bausteine united in very different ways. Some of them contain Bausteine of many kinds. The multiplicity of the proteins is determined by many causes, first through the differences in the nature of the constituent Bausteine; and secondly, through differences in the arrangement of them. The number of Bausteine which may take part in the formation of the proteins is about as large as the number of letters in the alphabet. When we consider that through the combination of letters an infinitely large number of thoughts may be expressed, we can understand how vast a number of the properties of the organism may be recorded in the small space which is occupied by the protein molecules. It enables us to understand how it is possible for the proteins of the sex-cells to contain, to a certain extent, a complete description of the species and even of the individual. We may also comprehend how great and important the task is to determine the structure of the proteins, and why the biochemist has devoted himself with so much industry to their analysis.

I think I may fairly make two postulata. First, That food is necessary to the existence of man. Secondly, That the passion between the sexes is necessary and will remain nearly in its present state. These two laws ever since we have had any knowledge of mankind, appear to have been fixed laws of our nature; and, as we have not hitherto seen any alteration in them, we have no right to conclude that they will ever cease to be what they are now, without an immediate act of power in that Being who first arranged the system of the universe; and for the advantage of his creatures, still executes, according to fixed laws, all its various operations.

I think it is a duty I owe to my profession and to my sex to show that a woman has a right to the practice of her profession and cannot be condemned to abandon it merely because she marries. I cannot conceive how women’s colleges, inviting and encouraging women to enter professions can be justly founded or maintained denying such a principle.
(From a letter Brooks wrote to her dean, knowing that she would be told to resign if she married, she asked to keep her job. Nevertheless, she lost her teaching position at Barnard College in 1906. Dean Gill wrote that “The dignity of women’s place in the home demands that your marriage shall be a resignation.”)

I’m tired of that stupid phrase, “the birds and the bees” which is supposed to represent “the facts of life” or the beginnings of the sex instruction of the young. … Well for heaven’s sake, has anyone ever tried to explain sex by talking about the birds and the bees? What have the birds and the bees to do with it? IT’S THE BEES AND THE FLOWERS. Will you get that through your head? IT’S THE BEES AND THE FLOWERS. The bee travels to one flower and picks up pollen from the stamens. The pollen contains the male sex cells of the plant. The bee then travels to another flower (of the same species) and the pollen brushes off onto the pistil, which contains the female sex cells of the plant. … Now in the human being … we don’t rely on bees to do it for us.

In order that an inventory of plants may be begun and a classification of them correctly established, we must try to discover criteria of some sort for distinguishing what are called “species”. After a long and considerable investigation, no surer criterion for determining species had occurred to me than distinguishing features that perpetuate themselves in propagation from seed. Thus, no matter what variations occur in the individuals or the species, if they spring from the seed of one and the same plant, they are accidental variations and not such as to distinguish a species. For these variations do not perpetuate themselves in subsequent seeding. Thus, for example, we do not regard caryophylli with full or multiple blossoms as a species distinct from caryophylli with single blossoms, because the former owe their origin to the seed of the latter and if the former are sown from their own seed, they once more produce single-blossom caryophylli. But variations that never have as their source seed from one and the same species may finally be regarded as distinct species. Or, if you make a comparison between any two plants, plants which never spring from each other's seed and never, when their seed is sown, are transmuted one into the other, these plants finally are distinct species. For it is just as in animals: a difference in sex is not enough to prove a difference of species, because each sex is derived from the same seed as far as species is concerned and not infrequently from the same parents; no matter how many and how striking may be the accidental differences between them; no other proof that bull and cow, man and woman belong to the same species is required than the fact that both very frequently spring from the same parents or the same mother. Likewise in the case of plants, there is no surer index of identity of species than that of origin from the seed of one and the same plant, whether it is a matter of individuals or species. For animals that differ in species preserve their distinct species permanently; one species never springs from the seed of another nor vice versa.

In order to drive the individuals towards reproduction, sexuality had therefore to be associated with some other devices. Among these was pleasure. … Thus pleasure appears as a mere expedient to push individuals to indulge in sex and therefore to reproduce. A rather successful expedient indeed as judged by the state of the world population.

In our preoccupations with sex, our submission to gods and leaders, our sometimes suicidal commitment to ideas, religions, and trivial details of cultural style, we become the unconscious creators of the social organism’s exploits.

Instead of being presented with stereotypes by age, sex, color, class, or religion, children must have the opportunity to learn that within each range, some people are loathsome and some are delightful.

It is one thing to say, “Some men shall rule,” quite another to declare, “All men shall rule,” and that in virtue of the most primitive, the most rudimentary attribute they possess, that namely of sex.

Like the furtive collectors of stolen art, we [cell biologists] are forced to be lonely admirers of spectacular architecture, exquisite symmetry, dramas of violence and death, mobility, self-sacrifice and, yes, rococo sex.

Meine Herren, I do not see that the sex of the candidate is an argument against her admission as a Privatdozent. After all, the Senate is not a bathhouse.
Objecting to sex discrimination being the reason for rejection of Emmy Noether's application to join the faculty at the University of Gottingen.

Men, accustomed to think of men as possessing sex attributes and other things besides, are accustomed to think of women as having sex, and nothing else.

My whole life is devoted unreservedly to the service of my sex. The study and practice of medicine is in my thought but one means to a great end, for which my very soul yearns with intensest passionate emotion, of which I have dreamed day and night, from my earliest childhood, for which I would offer up my life with triumphant thanksgiving, if martyrdom could secure that glorious end:— the true ennoblement of woman, the full harmonious development of her unknown nature, and the consequent redemption of the whole human race.

On the one hand, then, in the reproductive functions proper—menstruation, defloration, pregnancy and parturition—woman is biologically doomed to suffer. Nature seems to have no hesitation in administering to her strong doses of pain, and she can do nothing but submit passively to the regimen prescribed. On the other hand, as regards sexual attraction, which is necessary for the act of impregnation, and as regards the erotic pleasures experienced during the act itself, the woman may be on an equal footing with the man.

Philosophy is to science as pornography is to sex: it is cheaper, easier and some people prefer it.

Physics is to mathematics what sex is to masturbation.

Reproduction is so primitive and fundamental a function of vital organisms that the mechanism by which it is assured is highly complex and not yet clearly understood. It is not necessarily connected with sex, nor is sex necessarily connected with reproduction.

Science and engineering students presumably are left to learn about their literature in the same way they learn about sex.

Science and politics become the hobby of, and are cherished only by, the elect few; but religion becomes, through education, the property of all, without reference to station, age, and sex.

Science is like sex: sometimes something useful comes out, but that is not the reason we are doing it.

Sex appeal is a matter of chemistry, but you don't have to be a chemist to find the formula.

Sex is a natural function. You can’t make it happen, but you can teach people to let it happen.

Sex is the best form of fusion at room temperature.

Sexual instinct—as emotion, idea, and impulse—is a function of the cerebral cortex. Thus far no definite region of the cortex has been proved to be exclusively the seat of sexual sensations and impulses.

The best sex education for kids is when Daddy pats Mommy on the fanny when he comes home from work.

The enchanting charms of this sublime science reveal only to those who have the courage to go deeply into it. But when a woman, who because of her sex and our prejudices encounters infinitely more obstacles that an man in familiarizing herself with complicated problems, succeeds nevertheless in surmounting these obstacles and penetrating the most obscure parts of them, without doubt she must have the noblest courage, quite extraordinary talents and superior genius.

The male's difficulties in his sexual relations after marriage include a lack of facility, of ease, or of suavity in establishing rapport in a sexual situation.

The marriage of reason and nightmare which has dominated the 20th century has given birth to an ever more ambiguous world. Across the communications landscape move the specters of sinister technologies and the dreams that money can buy. Thermonuclear weapons systems and soft drink commercials coexist in an overlit realm ruled by advertising and pseudoevents, science and pornography. Over our lives preside the great twin leitmotifs of the 20th century—sex and paranoia.

The modesty of women, which, in its most primitive form among animals, is based on sexual periodicity, is, with that periodicity, an essential condition of courtship.

The precise equivalence of the chromosomes contributed by the two sexes is a physical correlative of the fact that the two sexes play, on the whole, equal parts in hereditary transmission, and it seems to show that the chromosomal substance, the chromatin, is to be regarded as the physical basis of inheritance. Now, chromatin is known to be closely similar to, if not identical with, a substance known as nuclein (C₂₉H₄₉N₉O₂₂, according to Miescher), which analysis shows to be a tolerably definite chemical compased of nucleic acid (a complex organic acid rich in phosphorus) and albumin. And thus we reach the remarkable conclusion that inheritance may, perhaps, be effected by the physical transmission of a particular chemical compound from parent to offspring.

The range of variation in the female far exceeds the range of variation in the male.

The Reproductions of the living Ens
From sires to sons, unknown to sex, commence...
Unknown to sex the pregnant oyster swells,
And coral-insects build their radiate shells...
Birth after birth the line unchanging runs,
And fathers live transmitted in their sons;
Each passing year beholds the unvarying kinds,
The same their manners, and the same their minds.

The second great channel through which the impulse towards the control of procreation for the elevation of the race is entering into practical life is by the general adoption, by the educated—of methods for the prevention of conception except when conception is deliberately desired.

The weakness of men in comparison with women lies in the great intensity of their sexual desires. Man becomes dependent upon woman, and the more, the weaker and more sensual he becomes; and this just in proportion as he becomes neuropathic.

There is a tendency to consider anything in human behavior that is unusual, not well known, or not well understood, as neurotic, psychopathic, immature, perverse, or the expression of some other sort of psychologic disturbance.

To connect the dinosaurs, creatures of interest to everyone but the veriest dullard, with a spectacular extra­terrestrial event like the deluge of meteors … seems a little like one of those plots that a clever publisher might concoct to guarantee enormous sales. All the Alvarez-Raup theories lack is some sex and the involvement of the Royal family and the whole world would be paying attention to them.

Too early and perverse sexual satisfaction injures not merely the mind, but also the body; inasmuch as it induces neuroses of the sexual apparatus (irritable weakness of the centres governing erection and ejaculation; defective pleasurable feeling in coitus), while, at the same time, it maintains the imagination and libido in continuous excitement.

Under pressure from the computer, the question of mind in relation to machine is becoming a central cultural preoccupation. It is becoming for us what sex was to the Victorians—threat and obsession, taboo and fascination.

We may lay it down that a happy person never phantasises, only an unsatisfied one... The motive forces of phantasies are unsatisfied wishes, and every single phantasy is the fulfilment of a wish, a correction of unsatisfying reality. These motivating wishes vary according to the sex, character and circumstances of the person who is having the phantasy; but they fall naturally into two main groups. They are either ambitious wishes, which serve to elevate the subject's personality; or they are erotic ones. It was shocking when Nietzsche said this, but today it is commonplace; our historical position—and no end to it is in sight—is that of having to philosophise without 'foundations'.

What we call “Progress” is the exchange of one Nuisance for another Nuisance.

While up to this time contrary sexual instinct has had but an anthropological, clinical, and forensic interest for science, now, as a result of the latest investigations, there is some thought of therapy in this incurable condition, which so heavily burdens its victims, socially, morally, and mentally. A preparatory step for the application of therapeutic measures is the exact differentiation of the acquired from the congenital cases; and among the latter again, the assignment of the concrete case to its proper position in the categories that have been established empirically.

With respect of the development of physiological love, it is probable that its nucleus is always to be found in an individual fetich (charm) which a person of one sex exercises over a person of the opposite sex.