Once upon a time (that has yet to happen) an interdimensional rummager stumbled upon a startling coincidence involving the planet Earth. The most advanced organisms there, humans, regarded themselves most fundamentally in terms of how they reproduced: via two sexes. In the Earth language called Science those two sexes were chemically identified via a shorthand code which looked like this:
XX | XY
When they discussed this aloud the humans would say:
ĕks-ĕks | ĕks-wī
“Hey!” exclaimed the rummager, “That’s my name!” Actually, the rummager had a different name in each of the almost-infinite entangled universes and ĕks-ĕks ĕks-wī was his name in only one of them. And there were only 420,662,831 universes where humans described themselves as XX | XY so the coincidence was quite remarkable.
Discoveries of the improbable were highly regarded amongst his [let’s just say] society of interdimensional rummagers and they all loved to brag and show off. Only yesterday one of his friends, %==>, had found a star with 37 sunspots in exactly the same pattern as his 37 anuses. %==> went inside the star and adjusted his size and orientation so that his anuses were perfectly superimposed on the sunspots. The effect was simply spectacular, everyone agreed. Another friend, c***, just that morning had found a planet that tasted like peppermint when you sucked on it, but when you bit down you got a blast of coffee and chocolate that just made your eyes water, it was so good. c*** tracked down several thousand universes with chemically identical versions of that bonbon planet, scooped them all up and handed them out to the whole gang. Let me tell you, c*** was worshipped like a god for several seconds after that tasty miracle.
ĕks-ĕks ĕks-wī’s phonetic congruence with a minor species was, in comparison, looking pretty lame. He decided to spend a few days poking around inside the heads of a few random humans to see if he couldn’t find the second half of an interesting anecdote.
By the time ĕks-ĕks ĕks-wī climbed out of the humans’ brains he was profoundly confused. These creatures always reproduced by pairing an XX specimen with an XY specimen. The basic FACT of this planet-wide scheme seemed clear and simple, whereas concomitant TRUTH seemed to be hard wired to a dimmer switch malfunctioning in a plasma storm. The contradictions made him wonder if he wasn’t going a bit mental.
He didn’t want to embarrass himself in front of all the rummagers, so he consulted with his close friends %==> and c***. “These humans,” ĕks-ĕks ĕks-wī reported, “typically interact as a single species, but occasionally behave as if they are two distinct species of animals. For instance, an XY human and an XX human will work together amicably to accomplish a task. Five minutes later the XY suggests that it is a good time to copulate, but the XX suddenly perceives the XY as an alien species and wants to punch the XY in the throat. A day later they perceive one another as a single species and copulate. Another day later it is the XY who regards the XX as a hostile species and the XY flees from all physical and electronic contact. The humans constantly oscillate between these two states! Weird. It was almost… almost, as though there were two distinctly different Earths, in two parallel dimensional planes, which had fused into a single actuality.”
%==> and c*** were incredulous. “You’re high.” “There’s no such thing.” After some cajoling ĕks-ĕks ĕks-wī convinced them to go take a look for themselves, explore the species from the inside out, and see what’s what.
Several days later they reported back to ĕks-ĕks ĕks-wī. c*** said, “Hey, buddy, I hope you haven’t been telling anyone else that you found two alternate realities from two parallel dimensions fused into one actuality. It just isn’t true, of course.”
%==> agreed, and added, “Humans are clearly comprised of two distinct sub-species, exhibiting physical dimorphism and psychological duality at all times. It’s perfectly obvious. One sub-species is built on the chemistry of XX and the other is built using XY. Exceptions to this dichotomy are exceedingly rare. These two sub-species regard one another as incompatible aliens. All the time.”
“Wait, wait, wait,” said c***. “What the hell are you talking about. Yes, they have two different chemical descriptors floating around in their cells, but XX organisms and XY organisms are physically identical at birth and they have identical behavioural instincts. Physical and behavioural differences are superficial and transitory, and are entirely the result of cognitive disease. This XX, XY chemistry is completely arbitrary. It’s about as arbitrary as which anus you used to take a shit this morning.”
Interdimensional rummagers do not enjoy conflict escalation, so for a few seconds they just blinked at each other and rattled their ganglions together like a pile of marbles till they could make sense of this bizarre discrepancy.
ĕks-ĕks ĕks-wī, it transpired, had examined the human contents of a single office building in Kyoto. %==>, however, had scurried amongst the brains of all eight billion humans, thereby perceiving an acute XX vs. XY dichotomy. c***, who had perceived no differences between XX and XY, had poked around inside a single skull, that of a tenured professor of gender studies at the Massachusetts Institute of Technology.
The three rummagers could plainly see that their three very different assessments of the human species were completely at odds with one another.
What to do, what to do.
“Ah-hah!” they all projected in unison. They would do a Contingency Experiment. They quickly checked with the Ethical Review Board to see if it would be okay to run an experiment which exterminated eight billion humans. Their proposal was – as expected – swiftly approved, receiving an evaluation of: No prob. Go for it.
First, they needed to scan zillions of zillions of dimensions to find another Earth nearly identical to the one they were just looking at. They found an Earthˊ which differed only in some minor turbulence patterns near the planetary core, ripples that would not affect the planetary surface for at least 200 million years. Perfect, because they expected their experiment to last only about ten million years. Even more perfect, Earth and Earthˊ were connected by a relatively short tachyon portage so they wouldn’t work up a sweat running up and down the hallway to make observations.
Of course, %==> and c*** agreed to let ĕks-ĕks ĕks-wī do the fun extermination part. %==> and c*** grabbed onto the tachyon portage to steady it and yelled, “Okay, go!” ĕks-ĕks ĕks-wī simultaneously raced down either end of the portage. At one Earth he murdered all of the XY humans, mostly by fouling the sinoatrial node that causes the heart to beat, but he also used some other techniques on zygotes and embryos. At the other Earth he simultaneously murdered all of the XX humans. As soon as ĕks-ĕks ĕks-wī got back into one piece his friends let go of the tachyon portage and it went back to doing its usual thing.
They moseyed down the portage to check out the dead-XX version of Earth. They observed three billion men and boys screaming and shaking the inert bodies of women and girls and baby girls. (A billion men and boys were asleep.) Here and there machines were crashing and falling out of the sky.
Then they loped over to the dead-XY version of Earth and saw three billion women and girls screaming and shaking the inert bodies of men and boys and baby boys. On this Earth there seemed to be many more machines crashing and lots more machines falling out of the sky.
“Huh,” they all thought. “We should count these crashes.” Then they went to lunch, agreeing to come right back and count crashes on a full stomach.
Fifty years later they returned to the tachyon portage to check on their Contingency Experiment, wondering if they would be able to detect any major differences in the trajectories of the two populations of humans – all XX on one Earth and all XY on the other – in so short a time.
On one of the Earths the human species was nearly extinct. Only about forty-thousand people remained, scattered among several hundred isolated tribes. The only light they produced was from fire.
On the other Earth there were 250 million people. And they had jet packs.