One of the more interesting attempts at explaining sex, made by a handful of (celibate) wizards stranded on an ancient island together with their female housekeeper, where an atheistic god is busying himself with creating living beings and inventing evolution. Perhaps also a nice theory of how life came up with the very idea of sex.

The excerpt is taken from "The Last Continent", by Terry Pratchett, one of the books in his "Discworld" series. I can wholeheartedly recommend all of his books, a great and very amusing read full of finest British humor. If interested, you can basically start off with every of the books, as they do have a connecting storyline, but it is a loose one. Nevertheless, I point you to this reading guide, by Krzysztof K. Kietzman.

'Amazin' piece of work,' said Ridcully, emerging from the elephant. 'Very good wheels. You paint these bits before assembly, do you?'
'It's not a kit, sir,' said Ponder, taking a kidney out of his hands and wedging it back in. It's a real elephant under construction!'
'Oh.'
'Being made, sir,' said Ponder, since Ridcully didn't seem to have got the message. 'Which is not usual.'
'Ah. How are they normally made, then?'
'By other elephants, sir.'
'Oh, yes . . .'
'Really? Are they?' said the god. 'How? Those minks are pretty nimble, even if I say so myself, but not really very good for delicate work.'
'Oh, not made like that, sir, obviously. By . . . you know . . . sex . . .' said Ponder, feeling a blush start.
'Sex?'
Then Ponder thought: Mono Island. Oh dear . . .
'Er . . . males and females . . .' he ventured.
'What are they, then?' said the god. The wizards paused.
'Do go on, Mister Stibbons,' said the Arch-chancellor. 'We're all ears. Especially the elephant.'
'Well . . .' Ponder knew he was going red. 'Er . . . well, how do you get flowers and things at the moment?'
'I make them,' said the god. 'And then I keep an eye on them and see how they function and then when they wear out I make an improved version based on experimental results.' He frowned. 'Although the plants seem to be acting very oddly these days. What's the point of these seeds they keep making? I try to discourage it but they don't seem to listen.'
'I think . . . er . . . they're trying to invent sex, sir,' said Ponder. 'Er . . . sex is how you can . . . they can . . . creatures can . . . they can make the next . . . creatures.'
'You mean . . . elephants can make more elephants?'
'Yes, sir.'
'My word! Really?'
'Oh, yes.'
'How do they go about that? Calibrating the ear-waggling is particularly time-consuming. Do they use special tools?'
Ponder saw that the Dean was staring straight up at the ceiling, while the other wizards were also finding something apparently fascinating to look at that meant they could avoid one another's gaze.
'Um, in a way,' said Ponder. He knew that a sticky patch lay ahead and decided to give up. 'But really I don't know much about—'
'And workshops, presumably,' said the god. He took a book from his pocket and a pencil from behind his ear. 'Do you mind if I make notes?'
'They . . . er . . . the female . . .' Ponder tried.
'Female,' said the god obediently, writing this down.
'Well, she . . . one popular way . . . she . . . sort of makes the next one . . . inside her.'
The god stopped writing. 'Now I know that's not right,' he said. 'You can't make an elephant inside an elephant—'
'Er . . . a smaller version . . .'
'Ah, once again I have to point out the flaw. After a few such constructions you'd end up with an elephant the size of a rabbit.'
'Er, it gets bigger later . . .'
'Really? How?'
'It sort of . . . builds itself . . . er . . . from the inside . . .'
'And the other one, the one that is not the, uh, female? What is its part in all this? Is your colleague ill?'
The Senior Wrangler hammered the Dean hard on the back.
'It's all right,' squeaked the Dean, '. . . often have . . . these . . . coughing fits . . .'
The god scribbled industriously for a few seconds, and then stopped and chewed the end of his pencil thoughtfully.
'And all this, er, this sex is done by unskilled labour?' he said.
'Oh, yes.'
'No quality control of any description?'
'Er, no.'
'How does your species go about it?' said the god. He looked questioningly at Ponder.
'It. . . er . . . we . . . er . . .'Ponder stuttered.
'We avoid it,' said Ridcully. 'Nasty cough you've got there, Dean.'
'Really?' said the god. 'That's very interesting. What do you do instead? Split down the middle? That works beautifully for amoebas, but giraffes find it extremely difficult, I do know that.'

'What? No, we concentrate on higher things,' said Ridcully. 'And take cold baths, healthy morning runs, that sort of thing.'
'My goodness, I'd better make a note of that,' said the god, patting his robe. 'How does the process work, exactly? Do the females accompany you? These higher things . . . How high, precisely? This is a very interesting concept. Presumably extra orifices are required?'
'What? Pardon?' said Ponder.
'Getting creatures to make themselves, eh? I thought this whole seed business was just high spirits but, yes, I can see that it would save a lot of work, a lot of work. Of course, there'd have to be some extra effort at the design stage, certainly, but afterwards I suppose it'd practically run itself' The god's hand blurred as he wrote, and he went on, 'Hmm, drives and imperatives, they're going to be vital . . . er . . . How does it work with, say, trees?'
'You just need Ponder's uncle and a paintbrush,' said the Senior Wrangler.
'Sir!' said Ponder hotly.
The god gave them both a look of intelligent bewilderment, like a man who had just heard a joke told in a completely foreign language and isn't sure if the speaker has got to the punchline yet. Then he shrugged.
'The only thing I think I don't quite understand', he said, 'is why any creature would want to spend time on all this . . .' he peered at his notes, 'this sex, when they could be enjoying themselves . . . Oh dear, your associate seems to be choking this time, I'm afraid . . .'
'Dean!' shouted Ridcully.
'I can't help noticing', said the god, 'that when sex is being discussed your faces redden and you tend to shift uneasily from one foot to the other. Is this some sort of signal?'
'Erm . . .'
'If you could just tell me how it all works . . .'
Embarrassment filled the air, huge and pink. If it were rock, you could have carved great hidden rose-red cities in it.
Ridcully smiled a petrified smile. 'Excuse us,' he said. 'Faculty meeting, gentlemen?'
Ponder watched the wizards go into a huddle. He could hear a few phrases above the susurration.
'. . . my father said, but of course I didn't believe . . . never raised its ugly head . . . Dean, will you shut up? We can't very well . . . cold showers, really'
Ridcully turned back and flashed the stony smile again. 'Sex is, er, not something we talk about,' he said.
'Much,' said the Dean.
'Oh, I see,' said the god. 'Well, a practical demonstration would be so much more comprehendable.'
'Er, we weren't, er . . . planning a . . .'
'Coo-eee! There you are, gentlemen!'
Mrs Whitlow entered the cave. The wizards went suddenly quiet, sensing in their wizardry minds that the introduction of Mrs Whitlow at this point was an electric fire in the swimming pool of life.
'Oh, another one of you,' said the god brightly. He focused. 'Or a different species, perhaps?'
Ponder felt that he had to say something. Mrs Whitlow was giving him a Look.
'Mrs, er, Whitlow is, er, a lady,' he said.
'Ah, I shall make a note of it,' said the god. 'And what sort of thing do they do?'
They're, um, the same species as, er, us,' said Ponder, miserably. 'Um . . . the . . . um . . .'
'Weaker sex,' Ridcully supplied.
'Sorry, you've lost me there,' said the god.
'Er . . . she's, um, er, a . . . of the female persuasion,' said Ponder.
The god smiled happily. 'Oh, how very convenient,' he said.
'Excuse me,' said Mrs Whitlow, in as sharp a tone as she cared to use around the wizards, 'but will someone introduce this gentleman to me?'
'Oh, yes, of course,' said Ridcully. 'Do excuse me. God, this is Mrs Whitlow. Mrs Whitlow, this is God. A god. God of this island, in fact. Uh . . .'
'Charmed, Ai'm sure,' said Mrs Whitlow. In Mrs Whitlow's book, gods were socially very acceptable, at least if they had proper human heads and wore clothes; they rated above High Priests and occupied the same level as Dukes.
'Should Ai kneel?' she said.
'Mwaaa,' whimpered the Senior Wrangler.
'Genuflection of any sort is not required,' said the god.
'He means no,' said Ponder.
'Oh, as you wish,' said Mrs Whitlow. She extended a hand.
The god grasped it and waggled her thumb backwards and forwards.
'Very practical,' he said. 'Opposable, I see. I think I should make a note of this. Do you brachiate? Are you bipedal by habit? Oh, I notice your eyebrows go up, too. Is this a signal of some sort? I also note that you are a different shape from the others and don't have a beard. I assume that means you are less wise?'
Ponder saw Mrs Whitlow's eyes narrow and her nostrils flare.
'Is there some sort of problem, sirs?' she said. 'Ai followed your footprints to that funny boat, and this was the only other path, so—'
'We were discussing sex,' said the god enthusiastically. 'It sounds very exciting, don't you think?'
The wizards held their breath. This was going to make the Dean's sheets look very minor.
'It's not a subject on which Ai would venture an opinion,' said Mrs Whitlow carefully.

'Mwaa,' squeaked the Senior Wrangler.
'No one seems to want to tell me,' said the god irritably. A spark leapt from his fingers and blew a very small crater in the floor, and that seemed to shock him as much as it did the wizards.
'Oh dear, what can you think of me? I'm so sorry!' he said. 'I'm afraid it's a sort of natural reaction if I get a bit, you know . . . testy.'
Everyone looked at the crater. The rock bubbled gently by Ponder's feet. He didn't dare move his sandal, just in case he fainted.
'That was just . . . testy, was it?' said Ridcully.
'Well, it may have been more . . . vexed, I suppose,' said the god. 'I can't really help it, it's a god-given reflex. I'm afraid as a . . . well, species, we're not good with, you know, defiance. I'm so sorry. So sorry.' He blew his nose, and sat down on a half-finished panda. 'Oh, dear. There I go again . . .' A tiny bolt of lightning flashed off his thumb and exploded. 'I hope it's not going to be the city of Quint all over again. Of course, you know what happened there . . .'
'I've never heard of the city of Quint,' said Ponder.
'Yes, I suppose you wouldn't have,' said the god. 'That's the whole point, really. It wasn't much of a city. It was mostly made of mud. Well, I say mud. Afterwards, of course, it was mainly ceramics.' He turned a wretched face to them. 'You know those days you get when you just snap at everyone?'
Out of the corner of his eye Ponder had noticed that the wizards, in a rare show of unanimity, were shuffling sideways, very slowly, towards the door.
A much bigger thunderbolt blew a hole in the floor near the cave entrance.
'Oh dear, where can I put my face?' said the god. 'It's all subconscious, I'm afraid.'
'Could you get treatment for premature incineration?'
'Dean! This is not the time!'
'Sorry, Archchancellor.'
'If only they hadn't turned up their noses at my inflammable cows,' said the god, sparks fizzing off his beard. 'All right, I would agree that on hot days, in certain rare circumstances, they would spontaneously combust and burn down the village, but is that any excuse for ingratitude?'
Mrs Whitlow had been giving the god a long, cool stare. 'What exactly is it you wish to know?' she said.
'Huh?' said Ridcully.
'Well, Ai mean no offence, but Ai for one would like to get out of here without mai hair on fire,' said the housekeeper.
The god looked up. 'This male and female concept seems really rather promising,' he said, sniffing. 'But no one seems to want to go into detail . . .'
'Oh, that,' said Mrs Whitlow. She glanced at the wizards, and then gently pulled the god to his feet. 'If you will excuse me for one moment, gentlemen . . .'
The wizards watched them in even more shock than had attended the lightning display, and then the Chair of Indefinite Studies pulled his hat over his eyes.
'I daren't look,' he said, and added, 'What are they doing?'
'Er . . . just talking . . .' said Ponder.
'Talking?'
'And she's . . . sort of . . . waving her hands about.'
'Mwaa!' said the Senior Wrangler.
'Quick, someone, give him some air,' said Ridcully. 'Now she's laughing, isn't she?'
Both the housekeeper and the god looked around at the wizards. Mrs Whitlow nodded her head as if to reassure him that what she'd just told him was true, and they both laughed.
'That looked more like a snigger,' said the Dean severely.
'I'm not sure I actually approve of this,' said Ridcully, haughtily. 'Gods and mortal women, you know. You hear stories.'
'Gods turning themselves into bulls,' said the Dean.
'Swans, too,' said the Chair of Indefinite Studies.
'Showers of gold,' said the Dean.
'Yes,' said the Chair. He paused for a second. 'You know, I've often wondered about that one—'
'What's she describing now?'
'I think I'd rather not know, quite frankly.'
'Oh, look, someone please do something for the Senior Wrangler, will you?' said Ridcully. 'Loosen his clothing or something!'
They heard the god shout, 'It what?' Mrs Whitlow glanced around at the wizards and appeared to lower her voice.
'Did anyone ever meet Mr Whitlow?' said the Archchancellor.
'Well . . . no,' said the Dean. 'Not that I remember. I suppose we've all assumed that he's dead.'
'Anyone know what he died of?' Ridcully went on. 'Ah, quieten down . . . they're coming back . . .'
The god nodded cheerfully at them as he approached.
'Well, that's all sorted out,' he said, rubbing his hands together. 'I can't wait to see how it works in practice. You know, if I'd sat here for a hundred years I'd never have . . . well, really, no one could serious believe . . . I mean . . .' He started to chuckle at their frozen faces. 'That bit where he . . . and then she . . . Really, I'm amazed that anyone stops laughing long enough to . . . Still, I can see how it could work, and it certainly opens the door to some very interesting possibilities indeed . . .'
Mrs Whitlow was looking intently at the ceiling. There was perhaps just a hint in her stance and the way her rather expressive bosom moved that she was trying not to laugh. It was disconcerting. Mrs Whitlow never usually laughed at anything.
'Ah? Oh?' said Ridcully, edging towards the door. 'Really? Well done, then. So, I expect you don't need us any more, eh? Only we've got a boat to catch . . .'
'Yes, certainly, don't let me hold you up,' said the god, waving a hand vaguely. 'You know, the more I think about it, the more I can see that "sex" will solve practically all my problems.'
'Not everyone can say that,' said Ridcully gravely. 'Are you, er . . . joining us, Mrs, er, Whitlow?'
'Certainly, Archchancellor.'