After some Internet-assisted research I have found out that this story is "Drei Rätsel der Evolution" ("Three Evolutionary Enigmas"). It is a story in three parts, written by Brian Aldiss, in 1980. isfb lists it as "Three Revolutionary Enigmas", which is not quite right.
Translated to German by Tony Westermayr, it appeared in a paperback A4 anthology by publisher Goldmann, titled "Tor zu den Sternen" ("Gateway to the Stars") late in 1981 (at the price of 20 DM, i.e. 10 EUR today).
This was a special anthology whereby non-German writers would submit text that would be published in German even before the English version would be published. So the German translation of "Three Evolutionary Enigmas" appeared in print before the English original.
The story is divided as follows:
- Der Untergang der Gattung B ("The Fall of Species B")
- In den Hallen des Jenseits ("In the Halls of the Hereafter")
- Das archaische Heim des Geistes ("The Ancestral Home of Thought")
Three Evolutionary Enigmas
The Fall of Species B
It is zero dark thirty. John Stang is a war reporter. He is sitting in a tank driving to an airport, along with a bunch of troopers. He will accompany a mission to "bomb brown people and Allah worshippers back to the stone age" (Sergeant's words), using new weapons designed that attack the nervous system of the enemy directly (KLEWA - Kleinhirnwaffen, sounds like "clever", literally means "Cerebellum weapons"). The soldiers around him are brutish, unkempt, sexually frustrated, the atmosphere is Mordorian. The plane is a semi-biological entity covered in hair, dripping effluents. As the troops board the plane, a mystery figure appears from the shadows, telling Stang: "There is another way", which confuses him greatly.
While the plane is taking off and the troops are being whipped into a killing frenzy against the browns, Stang mentally rips himself apart thinking about the polarization of human nature (male/female, Sun/Moon, rational/dreamlike) and how catastrophe is near (the words Yin and Yang are not used but it's evidently a situation where Yang has decided to get rid of Yin once and for all). Then the Sergeant calls out to the soldiers over the intercom: A traitor is on board - shoot at sight. His name is Jesus Christ. And Jesus is called upon to reveal himself.
Stang, animated by something stronger than himself, gets up and towers over the troops. Gripping the intestinal tubing of flying pig, he fills everything with light. "There is another way". Some soldiers, too dehumanized to show surprise, shoot at him, but to no effect. His form, now female, grows to immense proportions and becomes a Tree reaching to the Moon.
In the Halls of the Hereafter
Barnes Atarver has won a prize: he can visit visit a dead person of his choice. He decides to visit Paul Gauguin. (The idea of talking to the dead is very Aldissian.) Atarver lives two hundred years after Gauguin, "in the 51st year of the Kayyranarth" (Google hit zero). This takes place presumably some time before The Fall of Species B.
While talking to Gaugin, deep rifts within humanity are revealed: Cro-Magnon, the rational brute, and Neanderthal, the dreamlike savage, are antithetical beings. The innocence of Cro-Magnon, i.e. the White Race, makes him insufferable, obsessed with tooling, steel and war. It is the consequence of an enlarged Neocortex. Gauguin much prefers Tahitians, descendants of Neanderthal (well, this is not anthropology). It is they who are the Real Humans. While Gauguin materializes gigantic portraits of sexually attractive Thaitians out of the surrounding space, he proposes that the only solution to avert complete destruction is to merge Yin and Yang into a single Ying, merge the world into a single hybrid sexual organ. But then it is time for Atarver to leave for the world of the living again.
The Ancestral Home of Thought
The scene takes place at the same time as The Fall of Species B. A bunker set in a desolate place, at night. It is home to a laboratory where scientists work on Project Vercore. The lab is situated "1506 m above sea level" on a high plateau (maybe indicating that it is near Thika, Kenya).
Mervyn Widdowson and Jay Ling are drinking coffee and talking about war news. Stockholm has been taking by the "Sickle" (a reference to the Soviets I would think). A bit later, as Mervyn is indulging in some heavy movie violence (this scene revealed something about Mervyn's mental health as movie violence was not nearly as prevalent in 1980 as it is today) he's called up by his boss, Neil Teilbard.
Neil wants to have a midnight talk about project Vercore. Mervyn thinks it is an enormous project about population statistics. Indeed Neil starts by talking about the results: that the project has shown that there are two fundamentally different types of human. First, those with dominant Neocortex, and then those with dominant Cerebellum. The large Neocortex, proper to western people indicates propensity to rational though. The large Cerebellum, proper to non-westerns, means irrationality and dream-driven behaviour. The photos shown make Mervyn reflect that the Neocortex looks like a parasite, a mushroom feeding on a healthy animal.
After Mervyn remands Neil that he is dabbling in dangerous racism, he is invited for The Talk outside the bunker. Neil reveals that the scientific evidence shows that Humanity is separated into two species, A, and B. A came out of Africa, occupied the Middle East, the Far East and the Americas. B later out of India moving West. A and B cannot peacefully live together. War is a natural consequence of the differing thinking patterns and wars are increasing in intensity. Worse, B is being rapidly bred out by A and its promiscuous behaviour. The rational action is to eradicate A as soon as possible, and this is what Vercore is all about. Mervyn is horrified that anyone would think about killing 3/4 of the human population. Neil is as horrified as Mervyn - but facts are facts. The Final Solution was the right approach: Jews being a mixture of A and B, cannot be trusted. Jay, being A, has to go too. Everything has been prepared - nationalism and war fever will make the undertaking possible. Discriminating weapons targeting the Cerbellum have been developed in highest secrecy (only the President and his close advisors have been informed). Diplomatic contact has been established with the Sickle, which is actually B, to gang up against Asia, Africa and other A-specific regions.
Mervyn completely loses it, kills his superior and begins to rant in the night. He is soon surrounded by guards. As their close in, they are interrupted by the light of the appearance of the immensely growing Cosmic Female Tree which finally merges Earth and Sky.
The story does not seem to have been re-edited or translated into anything other than German. isfdb lists it as appearing in "Best of Aldiss" in 1983 and in the magazine "New Pathways Into Science Fiction and Fantasy" in May 1989 only. For a "Best of", that is astonishing.
Bonus: The idea of the Cerebellum as center of Consciousness also appears in Frank Herbert's "Destination Void" (1965). Actual Cerebellum function seems to be general purpose supervised learning. (Hey, I am B, ok?)