Quoted from
http://www.backyardnature.net/j/o/homosex.htm
For, nothing is more experimental and broad-minded than Mother Nature. When you look at the Creation you clearly see that the Creator's plan is to create diversity at all levels of reality, and to evolve that diversity to ever higher levels of sophistication -- whether it's forming galaxies from hydrogen gas, or evolving life on Earth. Moreover, just about any strategy furthering those blossomings is acceptable.
Among plants, sometimes flowers possess both male and female sex organs, sometimes they are unisexual and on different plants, sometimes unisexual and on the same plants, sometimes flowers are designed so they can't self-pollinate, other times they have to pollinate themselves, and some plants skip the sex scene altogether by reproducing vegetatively.
Among animals we find everything from the male seahorse who carries the eggs, hatches them and takes care of the young, to the "polyandrous" Spotted Sandpiper whose females may lay up to four nests in a season, each equipped with a different male incubating the eggs. Of course the common earthworm is both male and female, and some snails sometimes mate with themselves, producing offspring.
The higher up the evolutionary scale you go, the kinkier it all gets. Among communities of mice and other mammals, when population density reaches a certain high level where diseases and famine threaten, not only does homosexual behavior appear but also parents begin killing their own offspring. It's always the case that the Creator chooses the welfare of the community over that of the individual. If you'd like to review online notes of a series of university lectures dealing with parent-offspring conflict, including infanticide and the effects of high population densities on higher mammals, go to
http://www-personal.umich.edu/~phyl/weektwelve.html
If you have access to a science library or can use a search engine artfully, references to technical, academic papers detailing homosexual behaviors in a wide variety of primates, from langurs to orangutans to pit-tailed macaques can be accessed at
www.androphile.org/preview/Library/Articles/Werner/Werner20.24.htm
Among human populations, homosexuality occurs at a certain rate in all populations. Thus homosexuality is natural and inevitable. Data suggests that homosexuality may be at least partly genetically determined. A semi-technical paper at the University of Texas with the title "Biological Correlates of being Gay - Biological Determinism?" is available at
www.utexas.edu/courses/bio301d/Topics/Gay/Text.html
In short, it's simply wrong to say that homosexual behavior is never natural.
Why would the Creator create this state of affairs among humans? I don't know, but my own experience with human gays is that, on the average, they are more sensitive, insightful and caring than the rest of us, so maybe that's enough of an answer right there.
Some examples of homosexuality in nature.