"Very little is actually unthinkable in the educated world"

A great deal, however is unspeakable.

Masatoshi Nei and Naoko Takezaki measured the genetic distance between one human race and another, and between those races and apes, treating chimpanzees as if they were another human race: "The Root of the Phylogenetic Tree of Human Populations" They found that the distance between races was quite large, typically around half the human chimpanzee distance or so. They also found that some races had considerably less genetic distance between that race and the hypothetical common ancestor of humans and chimpanzees than other races.

Like Galieo, they were asked to repent and recant, and did so.

From 1996 to 2003 that opinion was officially unspeakable, and may well still be unspeakable. Although in 2003 there was a substantial expansion of what is speakable on race, Nei's heresy does not appear to have been repeated.

So if the Medieval Catholic Church was explicitly theocratic, so is Harvard. Catholics are required to believe what the Church teaches, whatever that may be, and the Church is the final arbiter of what it teaches.

At the time that they published, it was permissible to believe that genetic differences between races were real and substantial, that races were diverse, but equal. The reaction to the proposition that some were more closely related to the common ancestor of man and ape was so hostile, that the existence of genetic differences between races was also prohibited. Rather suddenly official truth became that humans were diverse culturally but not genetically, that races were just labels for continent of origin, so that Persians are "Asians" and Chinese are also "Asians", so Chinese are supposedly the same race as Persians, which doctrine was quite suddenly imposed not just in Academia, but on everyone in the English speaking world, and I expect most of the rest of the world also. The main finding of their paper abruptly became impermissible after it was published. So everyone is required to believe what Harvard teaches, whatever it may be, even though it changes from time to time. Because this paper pissed off our elite, Muslims in England are "Asians", and the English have trouble figuring out what to call Chinese, since they are supposed to call them "Asians"also, but many Englishmen have trouble using a single word for two rather different categories. If only Nei had not attempted to estimate the distance between races and the hypothetical ancestor of man and ape, Britons would probably still be calling Muslims Muslims and Pakistanis Pakistanis.