...
Granted, there aren't many human telepaths nowadays, sighted or otherwise. In 300 years' time, despite hundreds of centuries' worth of time, will humans who are blind develop telepathy as a replacement sense? Which is partially unfair to say, Kirk's pilot episode dealt with esper and 6th sense abilities and if anyone genuinely had such ability, they're not going to talk about it. In part because it wouldn't take long for anybody to realize the anomaly. and all this took place decades before Troi's time, too. Makes me wonder when first contact with Betazed really took place...
In "The Empath":
KIRK: Without speech, how's she going to be able to understand us? Unless she's a telepath.
SPOCK: An unlikely possibility, Captain, since over ninety eight percent of the known telepathic species send thoughts as well as receive them. She's made no attempt to contact our minds.
Suppose there are exactly 50 known telepathic species when Spock makes that statement. If 49 telepathic species can send thoughts as well as receive them, exactly 98 percent can send as well as receive. If 50 telephatic species can send as well as recieve that would be exactly 100 percent, and Spock wouldn't say "over ninety eight percent".
If there were exactly 100 known telepathic species and 98 of them can send as well as receive, that would be exactly 98 percent. If 99 could send as well as receive, that would be exactly 99 percent, and Spock wouldn't say "over ninety eight percent".
So if there are exactly 457 known telepathic species and 447.86 of them can send as well as receive, that would be exactly 98 percent. If 452.43 could send as well as receive, that would be exactly 99 percent. So Spock could say "over ninety eight percent" if 448, 449, 450, 451, or 452 of them could send as well as receive.
If there were exactly 200 telepathic species, and 196 could send as well as receive, that would be exactly 98 percent. If 198 could send as well as receive, that would be exactly 99 percent, and Spock might say "over ninety eight percent" if the number of species that could send as well as receive was 197.
Thus I suspect that at least 200 telepathic species were known at the time of "The Empath" and thus the era of "Is There in Truth No Beauty".
Are humans counted as one of the telepathic species?
Miranda says:
MIRANDA: I spent four years on Vulcan studying their mental discipline.
Four years, even if they just recently ended, should go back to the time of "Where No Man Has Gone before" or even earlier.
SPOCK: Not correct, Doctor, although I am aware of your mind attempting to contact mine. Were you born a telepath?
MIRANDA: Yes. That is why I had to study on Vulcan.
POCK: Doctor Jones was born a telepath, Captain.
KIRK: Oh.
MIRANDA: Vulcan was necessary to my sanity.
SPOCK: What most humans generally find impossible to understand is the need to shut out the bedlam of other people's thoughts and emotions.
I think most viewers would think that Miranda should have been old enough to talk about her telepathy and how other people's thoughts and feelings overwhelmed her at least 20 years before the episode, and so telepathy should have been known to occur among some Earth humans a couple of decades before TOS.
But in "Where No Man Has Gone before":
KIRK: Extrasensory perception. Doctor Dehner, how are you on ESP?
DEHNER: In tests I've taken, my ESP rated rather high.
KIRK: I'm asking what you know about ESP.
DEHNER: It is a fact that some people can sense future happenings, read the backs of playing cards and so on, but the esper capacity is always quite limited.
DEHNER: Yes. Mitchell, too, except for his eyes. We're trying to find a reason for that now, and why, out of our whole crew, only certain people were affected.
SPOCK: I think we've found that answer, Doctor.
KIRK: You mentioned that tests show you have a high degree of extrasensory perception. So do the records of the others. Gary Mitchell has the highest esper rating of all.
DEHNER: lf you're suggesting there's anything dangerous
SPOCK: Before the Valiant was destroyed, its captain was frantically searching for ESP information on his crew.
DEHNER: Espers are simply people with flashes of insight.
SPOCK: Are there not also those who seem to see through solid objects, cause fires to start spontaneously?
DEHNER: There's nothing about it that could possibly make a person dangerous.
SPOCK: Doctor Dehner is speaking of normal ESP power.
DEHNER: Perhaps you know of another kind?
KIRK: Do we know for sure, Doctor, that there isn't another kind?
Spock and Kirk certainly experience forms of ESP not normal for Earth humans in later episodes and might already know of some examples which they don't happen to mention in reply to Dehner.
Nobody mentions telepathy as a type of ESP, though Mitchell later does develop telepathy. This indicates three possibilities.
1. No Earth humans are known to include telepathy among their ESP abilties.
2. Telepathy exists among Earth humans but is considered to be a separate category from ESP.
3. Telepathy is an ESP ability that some Earth humans have but nobody happens to mention it as a form of ESP in "Where No Man Has Gone before".
Considering when Miranda Jones started experiencing telepathy it is improbable that # 1 is true in the
Star Trek universe.
So I wonder how common telepathy is among Earth humans and whether it is common enough for Earth humans to be counted as a telepathic species.