Recent advances in molecular biology are revealing that we don't just share genes with animals through common ancestors, we share genes with animals every day, carried between species by viruses and microbes, silently swapping data with our genomes sometimes without us even knowing that we have had a "bug" introduced into our system.
This horizontal gene transfer has been going on for ever... and I think it is reasonable to assume that it happens the most often with the species we are most exposed to - meaning our pets, livestock, and perhaps also rats and mice. Could this help explain why we feel so very close to our animals? Because genetically we "are" them in so many ways? Does this explain the heights to which our empathy can reach with even creatures who are not closely related to us? Every year we catch colds and flues of animal origin. Often the virus has come via a bird. This has happened for millions of years. At the extreme, could this mean that part of us "knows" how to fly, in the same way that a fledgling bird knows, by instinct?
We are of course all animals. We share many metabolic pathways and enzymes with everything from roses to grasshoppers to ravens. When it comes to other mammals even the divergence of our phenotypes is minute compared with what unites us.
Emotions are an evolved response, they are the "programming" that guides an animal through its life. Sexual desire and it's rarely-mentioned twin, sexual aversion are the most basic emotions, and must be one of the most conserved by evolution across generations and species. It follows that many of the emotions connected to sexual attraction are similar between people and animals. So it is hardly surprising that sensitive people can read-through the species barrier (subject to caveats about projection and anthropomorphisation) and connect with animals in various ways including sexually. As we see with dogs, some animals at least are capable of reading through the species barrier in the other direction, including where sex is concerned.
One of the joys of zoophilia is that it reminds us we are animals. Sexual experiences with animals offer a sense of one-ness with the universe that created us, a sense of one-ness with the dazzling tapestry of evolution of life on this planet which created us. Nature is more transcendent and more godlike than any god we could invent for ourselves... and each of us should love it in every way we can, as long as we are alive to do so. Fucking and loving can, and perhaps should, go together in our love for nature.. the Pagans probably new this :)
There is a final twist to this.. our gut microbes contain more genetic material than our own cells contain. They are essential for our health, true symbionts. Nonetheless, our gut microbes farm us more than we farm them. For example they produce 1/3 of our testosterone. I wonder if that means they are also influencing who and what we have sex with?
Some references below: (heavy reading, wouldn't bother, didn't have time to find something better) dogsR
http://www.asbmb.org/asbmbtoday/asbmbtoday_article.aspx?id=48671
http://www.texscience.org/reports/sboe-tree-life-2009feb7.htm
Personally, I don't see a reason to suppose horizontal gene transfer has any direct influence on interspecies relationships other than microbial ones. Clearer hormonal and physiological similarities between mammals, as well as their close contact through domestication, are perfectly sufficient for that.
I prefer to think of it not as a supposition, but as a question.
"Nature is more transcendent and more godlike than any god we could invent for ourselves... and each of us should love it in every way we can, as long as we are alive to do so."
Well said.
Just a nitpick...Kynophile has already kind of spoken to this effect but I thought I would throw my science hat into the ring.
HGT barely has any effect on advanced eukaryotes like ourselves, and the genes that we may receive are more from prokaryotes (like bacteria) than other eukaryotes, even through viral intermediates. Even if HGT did have a major effect on us, the genetic basis of sexuality has not been conclusively demonstrated by science.
The gut bacteria thing too is questionable and not at all a certainty. But the idea of gut bacteria influencing human behavior (and not necessarily something as complex as engendering an unusual sexual attraction) is intriguing and deserving of investigation.
You are right, though, that eutherian placental mammals, practically by definition, share much of their genome with each other. It's kind of sexy to think that only 80 million years ago, at the start of our current phanerozoic era, our ancestors lived and bred successfully with the ancestors of horses and dogs (the boreoeutherian ancestors).
This makes me smile. Our most recent common ancestor with most of our partners lived among dinosaurs. Yet we share so much in common, even now. Glorious.
I am not sure we know much about what is getting transferred horizontally yet, but more is being discovered about it all the time. Time will tell.. Prokaryotes may be the vectors but given how promiscous bacteria are with their episomes, they could be picking up their genetic material from anywhere, third fourth or fifth hand.
I would be willing to bet that there are some part's of any given genome that are relatively "open source" and others that are more "proprietory".
I should add that there are some cases under investigation that look very much like either HGT or some other form of bizarre hybridisation between rather unlike eukaryotes.
For some of us, science is about exploring the boundaries of poorly understood things in a rational and evidence-based way driven by irrational curiosity. For others it is about refining and consolidating information lying closer to the "almost certainly true" end of the spectrum.
Meanwhile we have the many examples of eukaryotic parasites controlling their eukaryotic hosts in interesting ways... most famously toxicara and its effects on host behaviour, including possibly humans. http://www.vice.com/read/how-a-cat-parasite-affects-your-behavior-mental-health-sex-drive
I never thought of that before, but yes. Yes it is.
Pretty sure the biological basis is overly good pattern recognition - particularily the pattern causing sexual arousal.