For characteristics that we share with other primates, what would be your evidence that we would not be so heterogeneous in our inner workings?
Did you mean, what would be my evidence that we would be so heterogeneous?
Assuming that you did, it's not clear to me that we share the relevant characteristics with the other primates at the relevant level of abstraction. It's not known to me that a female chimpanzee would react well to a male she'd never met before putting his arm around her waist.
My understanding is that mating practices vary pretty widely among the primates. They have greater and lesser sexual dimorphism. They are more or less inclined to have harem-type arrangements.
Did you mean, what would be my evidence that we would be so heterogeneous?
Oops, I temporarily confused homogeneous and heterogeneous, actually. ;-)
Assuming that you did, it's not clear to me that we share the relevant characteristics with the other primates at the relevant level of abstraction.
Based on your examples, I'd say that where we disagree is on what the correct level of abstraction is. I would expect "arm around the waist" to vary in attractiveness by culture, but the attractiveness of "comfortable initiating touch" to vary a good bit less.
Followup to: Do you have High-Functioning Asperger's Syndrome?
LW reader Madbadger uses the metaphor of a GPU and a CPU in a desktop system to think about people with Asperger's Syndrome: general intelligence is like a CPU, being universal but only mediocre at any particular task, whereas the "social coprocessor" brainware in a Neurotypical brain is like a GPU: highly specialized but great at what it does. Neurotypical people are like computers with measly Pentium IV processors, but expensive Radeon HD 4890 GPUs. A High-functioning AS person is an Intel Core i7 Extreme Edition - with on-board graphics!
This analogy also covers the spectrum view of social/empathic abilities, you can think about having a weaker social coprocessor than average if you have some of the tendencies of AS but not others. You can even think of your score on the AQ Test as being like the Tom's Hardware Rating of your Coprocessor. (Lower numbers are better!).
If you lack that powerful social coprocessor, what can you do? Well, you'll have to run your social interactions "in software", i.e. explicitly reason through the complex human social game that most people play without ever really understanding. There are several tricks that a High-functioning AS person can use in this situation: