Ordinary people have three kinds of cones in their eyes, attuned to red, green, and blue, but a few people, mostly women, are tetrachromats, with four kinds of cones:
For years, researchers weren’t sure tetrachromacy existed. If it did, they stipulated, it could only be found in people with two X chromosomes. This is because of the genes behind color vision. People who have regular color vision have three cones, tuned to the wavelengths of red, green, and blue. These are connected to the X chromosome — most men have only one, but most women have two. Mutations in the X chromosome cause a person to perceive more or less color, which is why men more commonly have congenital colorblindness than women (if their one X chromosome has a mutation). But the theory stood that if a person received two mutated X chromosomes, she could have four cones instead of the usual three.
Note the use of most in that paragraph:
The original story stated that all men have one X and one Y chromosome and that all women have two X chromosomes. This statement neglected to include those with Klinefelter Syndrome and transgender individuals. We regret the error.
(Hat tip to T. Greer.)
The distinction between sex and gender.
XKCD tried to bypass the question for a survey, asking “Do you have a Y chromosome?”, and people still complained.
He goes on:
“We recently programmed Bucket, the IRC chat bot in #xkcd, to allow people set their gender so he can use pronouns for them. This ended up taking hundreds of lines of code, three pages of documentation, and six different sets of pronouns and variables…”
There’s a nice plan enacted here:
1) Make “gender” a more polite form of “sex”
2) Rewrite documents to use “gender” instead of “sex”
3) Define “gender” to be a personal choice and a social construction
Et voila, when someone says “men” they must have forgotten the transgendered and need to apologize.
What cracks me up is that people use gender all the time when they mean sex and do so because they think it is the polite thing to do. Then they fall into the trap of the definition of gender.
And they do talk about it.
Actually your cones are attuned to greenish-yellow, yellowish-green, and purple. This particular tetrachromat’s extra cone is apparently orange.
Here is how Wikipedia explains it:
I used Wikipedia’s own numbers and cross-referenced them with Wikipedia. 570, 550, and 430, roughly speaking. Yellow ends at 560, blue at 450.
This source puts yellow at 570 and green at 510. That would make it yellow, greenish-yellow, and indigo.