Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization

First Edition

© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm


12.3  Alien Sex Practices

We have examined just a few of the many possible variations in pairwise reproduction. Bisexual aliens, who may comprise the majority of higher lifeforms in this Galaxy, will undoubtedly display an even richer variety of reproductive styles than we can imagine.

But exactly how will biological ETs execute their sexual functions? The fundamental need for a joining of male and female is clear, but the details of this fascinating operation (e.g., Table 12.1) remain indeterminate where ETs are concerned. Of course, it is far too early in our exploration of space to be offering detailed speculations on this matter. Nevertheless, the grand diversity of sexual practices among the fauna on this planet can give us some idea of what to expect from aliens. Earth is typically exotic; terrestrial animals are typically peculiar.


Table 12.1 Approximate Coition Times for Various Animals
Coition Time
Coition Time
several seconds
30-60 sec.
several seconds
  Roman snail
2-3 minutes
3.8 sec.
2-120 min.
7-8 sec.
  Garter snake
10-20 min.
10 sec.
20-45 min.
10 sec.
up to 2 hours
10-15 sec.
up to 2 hours
Y. fever mosquito
(typical insect)
10-20 sec.
several hours
2-8 hours
12.4 sec.
2-8 hours
20-60 sec.
3-70 hours



Consequently, we may demolish the age-old myth that it is the male who always chases the female. In crickets, it is the female who courts the male and later mounts him. ETs may conduct themselves in similar fashion.

Another instance of the unusual: humans are not the only beings concerned with the virtuousness of their female mates. While men once fashioned chastity belts to keep their ladies safe, other creatures must improvise without the benefits of technology. The male garter snake, to take one example, is so suspicious of his companion’s attentions that he installs a "chastity belt" inside his mate after copulation. This hardened plug effectively ensures the fidelity and continued continence of the female.

Certainly one of the most outré sexual fashions on this planet is found in a small fish that lives in the upper strata of kelp beds in the sea. Shaped like the head of a chessboard knight, the tiny sea horse challenges our traditional conceptions of normality. In these curious creatures, it is the female who impregnates the male with her eggs, and the father who becomes pregnant and carries the child to term!

German naturalist Herbert Wendt describes how they mate:

Two sea horses ready for mating put on the tenderest and most charming of courtship spectacles. As among the closely related pipefish, the female is an active partner. In her resplendent wedding dress, far showier than the modest male, she dances around her mate and grasps him with her prehensile tail. Both swim through the water, head against head, in a close embrace, like human lovers. They sway to every side, rock back and forth, and then rise to the surface of the sea. Thereupon something altogether extraordinary happens. The male puffs up his abdomen so that it presents a kind of sac, and the female protrudes a sort of penis from her body.

With it, the female gropes about along the male’s body and tries to introduce it into an opening in his abdominal sac. An observer of this process cannot help feeling that the male is being fertilized by the female. But what is taking place is not breeding in the proper sense of the word, but only a transmission of eggs. The female wants to deposit her spawn in the male’s pouch. Again and again she thrusts her organ into the opening in the pouch and drops one egg after another inside. This act apparently exerts an irresistible stimulus upon the male. For at the same moment that the female’s "penis" enters his body, he pours his sperm into the brood pouch.

After a while the couple terminate their embrace. The female swims away, but the male sea horse has been "impregnated" and must now undertake the nourishing and raising of the brood. He continues to behave like a female. The embryos develop in his brood pouch. They hatch out there. And as the small sea horses grow, the father’s abdominal region swells like a balloon...1028

Actually, some form of copulatory organ, or "penis," has probably been around virtually since the invention of sex an eon ago. This organ has arisen independently in so many vertebrate, arthropodal and molluscan species as to suggest its tremendous utility in accomplishing the designated purpose. (Even the rare male rotifer has a ciliated sperm duct that could be viewed as an early version of the penis.2493)

Using a convergent evolution type of argument, we might advance the proposition that male penises will be common but not universal among alien races.

The vagina has a related, but more involved, evolutionary history. Most female animals which engage in copulation, up to and including the amphibians, the reptiles, most birds and the lower mammals, do not have any distinct reproductive organ.* Instead, these concupiscent creatures accept the male member in their cloaca, an opening which doubles as a passageway for the excretion of intestinal and liquid bodily wastes. Only in the higher mammals has the female evolved a sexual orifice separate from the anal and urethral tracts.

Males of various species, including frogs and many birds, also have a cloaca in place of the penis. The cloaca is a mere rear opening, used in mating as alternative to the penis-vagina combination. Like pressing two pairs of rubbery lips together in carnal embrace, sperm are transferred to the female by the "cloacal kiss."

Multiple organs are quite possible.** Some lizards and snakes exude not one but two penises during mating, although usually only one of these actually passes semen. These copulatory organs are "truly terrifying" in appearance, covered with spines, warts and hooks.

Snakes are also known to attend public orgies unabashed:

Among vipers and adders we will sometimes see a whole knot of males and females in sexual congress. The reptiles which have thus transformed themselves into a Gorgon’s head are attached in pairs, anus to anus, and if disturbed cannot extricate themselves from their tangle. They can do no more than extend their heads from the knot, hiss and strike at the disturber. Courageous foresters and rangers have sometimes amused themselves by gathering the whole hissing lot in a canvas bag and carrying them away.1028

Alien hermaphrodites may take after the Roman snail in their sex practices. In this Earthly organism, the major sex glands and penis are situated near the top of the body rather than in the lower regions near the sexual orifice. As simultaneous hermaphrodites, snails are two sexes in one, having at once both sperms and eggs. Copulation thus involves two penises (one from each partner) and two "vaginas" (again, one from each).

The loveplay of the Roman snail is shocking indeed:

Its penis is a gigantic, erectile generative tube, and its wooing is more passionate and tempestuous than any human Casanova’s. Moreover, the creature is apparently inclined to sadism. For after a wild love dance in which the partners rear up sole to sole, rock back and forth and even exchange regular smacking kisses, the excited snail suddenly releases a dagger of chalky material from a kind of quiver and drives it into the body of its mate. Other varieties shoot arrows of chalk at their victim-mates, and these are not aimed at the genital orifice, but are merely intended to wound some part of the mate’s body. The wounded snail visibly twitches with pain, and indeed the act seems like the prelude to a veritable sex murder. In fact the love daggers of the Roman and garden snails occasionally penetrate the lung or the abdominal wall of their partners, inflicting deadly wounds.

But so far we have described only one of the mates. The other behaves in exactly the same way during the sex act. It, too, is extremely excited, and its excitement mounts when it is struck by the love arrow. Whereupon the masochist likewise becomes a sadist; it too fires a dart or stabs with a dagger at the body of its partner. It too protrudes a huge penis. And after fierce efforts and writhings, each of the two inserts its member into the genital orifice of the other.

For several minutes the snails remain united in this mutual copulation. The male organ must penetrate as deeply as possible into the female genital canal in order to deposit the semen at the right place, in a bladder-shaped receptacle where it will fertilize the eggs some time later. Each partner in this act is both male and female. And both seem to discharge sperm at the same time. Then they separate and both snails drop exhausted to the ground, where they remain lying motionless for some time. At last they crawl away, each in a different direction.1028

Snails, then, appear also to experience that strange and wonderful phenomenon known as orgasm, an explosive discharge of muscular tension at the climax of sexual tension. We shall have more to say about this in regard to alien sex life in Section 12.3.1.

One might naturally suspect that hermaphrodites would enjoy even better orgies than the snakes. Since they have both female and male organs, snails, leeches and others are not limited to a single partner during the mating ritual. The European mud snail, and a variety of marine snail called Acera bullata, regularly form copulatory chains of as many as six mates among them selves. In these gastropodal "daisy chains," the lead snail serves only as a female. For the rest, each performs as a male for the one in front and as a female for the one behind. The last in line functions solely as a male.

The American slipper snail Crepidula fornicata has perfected this fine copulatory style:

Grown slipper snails are sessile, like most molluscs, but in their youth the animals are motile and all are males. Once a slipper snail attaches itself to some base for life, it transforms itself into a female. Soon it is mounted by a male and fertilized. The male settles on the female’s shell; a third snail mounts it, and so on until at last a tower of ten to fourteen individuals is established. The lowest and largest specimens in this tower are female; the middle ones will be gradually changing from males to females; and only the topmost indicates by its penis that it has remained a male.1028

What human sexual mores might regard as "perverted" is a way of life for the slipper snail. Whatever opinions we may harbor as to the propriety of these sexual practices are irrelevant -- for the snails, like the intelligent extraterrestrials we may encounter on another world someday, cannot change what they are.

Arthropods, those fearsome looking organisms with jointed legs and hard-shelled bodies, comprise roughly three-quarters of all known animal species on this planet. Carapaced creatures are the most prolific and diverse lifeforms on Earth.

They are also the most ruthless, murderous lovers.

The late French entomologist Jean H. C. Fabre observed two scorpions retiring to the nuptial nest:

The foreheads touch, bend a little to left and right, as if the two were whispering in each other’s ears. The little forelegs flutter in feverish caresses. What are they saying to each other? How shall we translate their silent epithalamium into words?

But connubial bliss hardly lasts until dawn:

The idyll of the evening is followed, during the night, by a hideous tragedy. Next morning, we find the scorpioness under the potsherd of the previous day. The little male is by her side, but slain, and more or less devoured. He lacks the head, a claw, a pair of legs. I place the corpse in the open, on the threshold of the home. All day long, the recluse does not touch it. When night returns, she goes out and, meeting the deceased on her passage, carries him off to a distance to give him a decent funeral, that is, to finish eating him.2491

The gold ground beetles have been described as "notorious nuptial cannibals." Having observed such a beetle pair mating, Fabre saw the female hurl herself at her mate in a savage attack as soon as the unfortunate suitor had finished his business:

A vain struggle to break away -- that is all the male undertakes toward his salvation. Otherwise, he accepts his fate. Finally the skin bursts, the wound gapes wide, the inner substance is devoured by his worthy spouse. Her head burrowing inside the body of her husband, she hollows out his back. A shudder that runs through the poor fellow’s limbs announces his approaching end. The female butcher ignores this; she gropes into the narrowest passages and windings in the thoracic cavity. Soon only the well-known little boat of the wing sheaths and the thorax with legs attached are left of the dead male. The husk, sucked dry, is abandoned.2496

The most hideous of all is the praying mantis, a ferocious centaur-like carnivorous insect that can grow to more than nine centimeters in length. These arthropod monsters have been known to attack and devour small frogs, birds and lizards, so it is hardly surprising to learn that their mates receive no better treatment:

I find, by themselves, a horrible couple engaged as follows. The male, absorbed in the performance of his vital functions, holds the female in a tight embrace. But the wretch has no head; he has no neck; he hardly has a body. The other, with her muzzle turned over her shoulder, continues very placidly to gnaw what remains of the gentle swain. And, all the time, that masculine stump, holding on firmly, goes on with the business!

Love is stronger than death, men say. Taken literally, the aphorism has never received a more brilliant confirmation. A headless creature, an insect amputated down to the middle of the chest, a very corpse, persists in endeavoring to give life. It will not let go until the abdomen, the seat of the procreative organs, is attacked....

The Mantis, in many cases, is never sated with conjugal raptures and banquets. After a rest that varies in length, whether the eggs be laid or not, a second male is accepted and then devoured like the first. A third succeeds him, performs his function in life, is eaten and disappears. A fourth undergoes a like fate. In the course of two weeks I thus see one and the same Mantis use up seven males. She takes them all to her bosom and makes them all pay for the nuptial ecstasy with their lives.2496

(Apparently the reflexes of male mantis copulation are restrained by the brain ganglia, so the organism must be decapitated to copulate.)

As enlightened and rational sentients, we are urged to ignore the wanton brutality and utter callousness of such mating behaviors. Cannibalism, the experts tell us, is a purely instinctual act. The mantis, the gold ground beetle and the scorpion are compelled to eat their-mates, not by cruel premeditation, but rather because of a biological urge that is simply irresistible for them -- "protein hunger."

But are humans capable of displaying such stolid, rational objectivity in the face of intelligent extraterrestrials known to eat their mates while copulating? Would we, could we, ever feel truly comfortable in the presence of such creatures? Will man be able to retain his sanity and businesslike demeanor long enough properly to conduct interstellar commerce with these beings?

Of course, not all animals are as deadly serious about their sex as the arthropods. Others consider it the purest of fun, such as the spritely orangutans:

Making smacking sounds with her tongue, the female loudly greeted the orang male sitting in the bed of straw. She put her arm around his shoulders and caressingly scratched his abdomen. Then she climbed up to the ceiling of the big enclosure and hung with all fours from a crossbeam, her hind legs straddled. The jungle giant straightened up to his full height and looked up longingly. One rapid movement and his hands grasped the beam. Body dangling, he swung toward his mate, who for her part loosened the prehensile toes of her spread legs and affectionately embraced him. He too now clasped her with his thighs and feet twined around her back. Breast to breast they mated, hanging by their hands and rocking back and forth.2497,2498

If there are sentient primate forms on other worlds, humans may find them selves at once embarrassed and challenged by the limberness of these distantly-related sexual acrobats.***


* In some jellyfish, the sperm enter through the female’s mouth and fertilize her eggs. Later, the larvae exit via the same route.2493

** Some male ostracods (mussel shrimp) have a double penis, and the females a double vagina. A few species of flatworm have up to twenty extra penises, although only one is customarily used for reproductive purposes.2493 Another peculiarity is the "pseudopenis" of the female hyena. When approaching a group, she wags it back and forth in a conspicuous display. This is a vital part of the greeting ceremony and pack communication among these dangerously aggressive animals.2499

*** Man has no monopoly on face-to-face copulation. Young chimpanzees often experiment with this position, although they soon give it up in favor of the more classic mammalian posture. Whales and other cetaceans, due to the turbulent nature of their watery medium, also must copulate belly-to-belly. Sailors have spotted pairs of blue whales leaping from the water, their midsections pressed tightly together in a few brief moments of airborne ecstasy. Beavers, too, sit upright in shallow water to copulate, facing each other and embracing with their arms like human couples kissing. Alternatively, beavers can drift along the surface of the water, holding each other lovingly breast to breast. Finally, most male crabs, crayfish and lobsters make love with the female lying on her back, and in many species of millipedes the couples lie abdomen to abdomen and hold each other with all of their many legs. It is unknown at present whether these examples constitute sufficient evolutionary convergence with humanity to warrant any conclusion as to the probable mating posture to be assumed by highly advanced alien lifeforms.


Last updated on 6 December 2008