Very interesting article with several points that could lead to discussions.
I am no expert but I'll throw a few things out there.
It's debatable if there are any other conscious species on the planet. I'm not sure we've actually defined the term conscious yet. People seem to have different ideas of what it exactly is.
Thinking in terms of Evolutionary Psychology, maybe we have sex in a cave rather than a field has something to do with how long we are in the act. When we are, we're in a vulnerable position and we're signaling that we are interested in sex. (If I recall, other animals sex act duration is short.) That signal would have some sort of affect on the thinking of the other members of the tribe. It can take up to 5 days from sex to conception and if someone else in the tribe wants to have children (instinctively), he may want to have sex with the same woman and the other man may end up raising the child. I think I've read that other animals employ such a strategy. Anyway just my thoughts and maybe an avenue of research for some EvoPsych postdoc out there!
Yes, consciousness is still being defined, but I was going with the more generic "the state of being awake and aware of one's surroundings" definition. Many animals are incredibly self-aware. Dolphins, for example, pass the mirror test, morn their dead, have all kinds of interesting sexual practices, etc. It's an interesting discussion.
Interesting thought about the length of the act. Would that suggest humans are unique in their approach to sex? That might be an interesting study, for sure.