Let me explain, werewolves (or at lest our brand) can transform into three different forms, and on some level regenerate, not to mention turn humans into werewolves as well. Those abilities alone qualifies it to be its own separate spices.
but that's just a start, humans have 23 chromosomes, and wolves have 78 chromosomes. Werewolves have to store the genetic code of three separate forms in each nucleus. How may I ask you, all of that information is contained with in 23 chromosomes? It can't, even when one piece of DNA can be responsible for more than one function (The main reason why genetic engineering hasn't made us into real life furries, or what ever) more "code" is needed.
This shuts down the theory that werewolves can mate with a human. Our genetic code and theirs isn't compatible. We can't fill the order to match the werewolf's DNA, even if they match the same chromosomes count, the code is too different. It's like finishing a program in C# but the rest is written in Java, it's not going to happen.
Even if they are an off branch of the human race, it would end up like the liger. For those who don't know a liger is the bastard child of a lion and a tiger, they only exists in captivity. The lion and tiger are two animals belonging to the feline family, they never been in contact with each other in the wild. Unlike wolves and dogs that similar enough to breed a healthy offspring. The tiger and loin are considered separate species, but apparently close enough to actually breed.
Here's the catch, the result of this unnatural breeding is riddled health problems, and most die before they are adults. Those that do make it to adult hood are often sterile, meaning that they can't reproduce.
Finally some of the stuff they do is unheard of in the natural world. Like changing a member of a different species into one of their own by making their own retro-virus, and shape shifting in a short amount of time. Animals in the natural world mimic to eat, and/or not be eaten. Like moths that mimics pheromones of honey bees to grab a meal, and an octopus that makes his body change colors and acts like other animals to avoid predators, but no known creature on earth can completely change it self physically to mimic another animal. Only thing on earth can come close is insects that take weeks to metamorphose to another form. What insects do in weeks werewolves can do better, change back at will, and a hell of a lot faster. It's unheard of!
Werewolves are just too different to be considered a human or even a wolf in that matter.
((Man, i can keep going, but i have to go. I'll post more of my argument later
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