First of all, I sincerely apologize for this. I'm quite surprised this came out of my head, really. Not meant to be a specific Doctor or companion, just his thoughts on human sex.
Humans were complicated, he mused. Sure, it was easy to think of them as relative children controlled by biological demands, but it was more than that. Letting his midbrain take over the physical, he continued this pondering.
Humans had managed to halt their evolution through technology and social codes, but they stopped at the most awkward point. It was like stopping someone's development in the middle of adolescence; one foot in need and impulse and instinct, the other in logic and consequences and philosophy. It didn't help that they were also raging telepathics.
That wasn't quite true. They were all transmitters, like a radio, but very few of them were receivers, and even those were tuned to the wrong station. It was overwhelming until he learned to shut them out. Imagine billions of radios blaring full volume, full time, straight into your mind.
Adolescent radios. That's were it got complicated. As involved as he was in the here and now, he automatically opened a chink in his mental armour. Her human mind hit him, and he saw all its complicity.
Sex and pain too often elicited the same response, he learned.
Skin and sweat and wonder/blood and teeth and violence.
He traced tender kisses down her neck, following her racing pulse, and making her growl/his teeth sunk hard into her flesh, hitting bone, and he pulled and twisted until her clavicle splintered into his mouth.
She was brilliant and beautiful, and when she offered herself to him, he was overcome with ecstasy and desire to make her happy/she was meat to be ripped apart, nothing more than a good fuck, submissive under his demand to be satisfied.
They were spiralling together, up or down, or possibly sideways, he couldn't tell nor did he want to, he just wanted to remain in this feeling of togetherness, of oneness, of rightness/he ignored her whimpers and fucked her hard enough to make her bleed, his teeth had torn holes in her chest, and it didn't matter if she died with him still inside, he would finish getting what he wanted.
Yes, humans were complicated.