Why can't we humans abduct both eyes simultaneously

That is right we can't abduct both eyes simultaneously. Why? Because the muscles are coupled! How?
Read this:
Extraocular Muscles

Where's the pituitary gland located?

"Halfway between the two fingers" was my answer to Pamu's question.
And then Shubham reminded us of the 3 idiots scene "What is the DEFINITION?" Where is it, ANATOMICALLY?

Fahad gave a quick reply. It's the hypophysis, it's in the hypophyseal fossa!
Well, that's right. But where's that?

And I turn to the cunningggg haammu,
"It lies posterosuperior to the sphenoidal air sinuses, below the optic chiasma, in front of the dorsum sellae, and has a cavernous sinus on each side of it."

Now, where on earth is THAT?

Enter "the middle cranial fossa"!

Oh yeah! That beautiful fossa which looks like somebody kept a dumbbell in there just before the skull bone became concrete or maybe a cooling glass is more like how it looks.
You want a photo? Here you must go en.wikipedia.org/wiki/File:Base_of_skull_22.jpg

Notice the median part, the small connection between the dumbbell lobes where its handle would have been. Yes, that is our focus. That's the hypophyseal fossa. And where our lovely pituitary is located. It's the sella turcica, the Turkish saddle, that the bone underneath it is called. (no, the bone is sphenoid)

"What lies to the front?"
"The eyes"
"Yeah, the eyes, but, just in front of the pituitary, I mean."
"oh yeah, I see two holes leading into where the eyes would have been"
"Marvelous! That, is the optic canal, where the optic nerve and ophthalmic artery goes through. And right before entering the hole they run through the slight depression between it and the hypophysis. And that is the sulcus chiasmatis"

And the optic nerves from both sides form the chiasma just over the, yes you said it, pituitary!

Note if you have a skull that the sella tursica is a bit elevated. Well, that's because there is the sphenoidal air sinus beneath it. See a superior view. en.wikipedia.org/wiki/File:Cavernous_sinus.png

Yes, and if you go towards the left or right from the pituitary, after leaving the sphenoid bike you reach the squamous part of temporal bone, and right behind that there is the petrous part in which the internal ear, the middle ear and the external acoustic meatus are all seen.
And if you come out still, right in front of the ear, you'll see my fingers, pointing right at the pituitary

Study resource for head and neck

Introductory page for head and neck

Skull, scalp and face, a general outline

Skull, Scalp and Superficial Face

The peculiar case of skull

The proportions of the various features of skull is different from what we'd expect them to be based on the external appearance of face. This is a very important observation to be made before learning about the structures in head.

The Halloween melon mask we make, is inaccurate. The skull is not just a sphere, it's a sphere with an equatorial plate. The nose and eye lie on the same line (this plate) though their geometry dislocates them anteriorly.

This insight must make things clear about the middle cranial fossa