The nature of things is to be in balance. The planetary environment (a.k.a. mother nature) maintains balance (within an unspecified range). For example, when a given species experiences a boom in population, they ultimately outgrow their food supply, and starvation among other things reduces the population back to the balanced range. Likewise, their food supply has just endured a population reduction, which takes pressure off it's food supply, which in turn grows in population, leading to the recovery of the population of the species that was eaten up by the initial booming species. All this says one thing: The balance fluctuates, but is maintained. Always. ...with one exception...
The introduction of non-indigenous species. Massive, virtually uncontrolled booms in the population of a species generally occur only when a species relocates to a new environment, finds a comfortable niche, but has no natural predators to keep its population in check. So, BOOM! Suddenly the beast is everywhere, knocking everything out of balance. In the looooooooong run, a new balance will be established and life will continue, but that is irrelevant in the scope of this essay.
My point is this. Humans have overrun the planet. This is largely due to a clear lack of effective predators. I already explained that this only happens when a transplantation has occurred. Well, humans function at the level of the global ecosystem so how could a transplantation have occurred? An inter-planetary transplant - we are from another world.
I have some additional circumstantial evidence as well. In my observations, each species of animal generally has one type of hair/fur. It may be longer or shorter in different places on their body, but fundamentally, it's type is unchanged. i.e. They don't have pubic hair. Caucasian humans on the other hand, often have a dramatic difference between their body/head hair and pubic hair, lighter skinned races as well. However the difference is not so dramatic in persons of African origin/black people. Note that Africa is pointed to as the origin of the Human race. So would it not make sense to see the "two hair types" anomaly as evidence of a mixing of species/races? But there is no evidence for the origin of humans of any type outside of Africa without emigration having brought humans there. An obvious explanation is the introduction of an alien/offworld species which mixed with the native African/black humans, resulting in humans with two hair types. In addition to this, the introduction appears to have altered the human species enough that it began functioning outside the natural balance and thus the resulting overrunning of the planetary ecosystem.
Furthermore, Caucasian cultures and individuals, historically display a drive for conquest and control at levels beyond what would be considered healthy for survival and prosperity; levels we don't see in any other animal. Nor in African cultures - as far as my limited knowledge goes. But as skin lightens, we begin to see this drive emerge around the world.
Do understand that these broad generalizations are for the sake of historical argument only and are not grounds for prejudice or much meaningful application at all regarding today's global human culture.
So yeah, we're alien hybrids...