Evolution is an odd thing. We are asked to believe in it, as we are asked to believe in a faith. Yes, there is much evidence that could lead one to the conclusion that over time species adapted and made changes for survival, but we also have no proof that variations just popped up that were beneficial and somehow bred those new traits to make them dominant. We are led to believe that survival happened by happenstance based on "defects" in some of the population.
Today, we have reports of all kinds of oddities in the cryptozoology world including variations of man with cow, horse, dog, ape, lizard, and more. Why would such creatures exist? There is no crossbreeding between species of such extreme incompatibility.
But, what if an alien culture (not necessarily intergalactic, perhaps of another world/dimension), were to come to earth, look upon the tools that were inherently here, and decide to use what was in the kitchen, so to say? They might develop and experiment with qualities, colors, traits, that would make it possible for them to survive given the presence of oxygen, the presence of gravity, the need for nourishment for energy, reproduction and more.
Perhaps aliens were truly the first xeriscapers, working with the elements that were here and finding ways to make it work. Variations of creatures were tried and tossed aside until ultimately, upon leaving, they decided to give the planet a sentient being that might some day be god of his own worlds as they had become.
Chimeras might be the result of many tries that failed, looking for the combination that would succeed once they were done tampering.
And how would relics of ancient giants fit into the evolutionary scenario? Ancient man was not exceedingly tall and yet reports historically in religious documents and from Native tribes report that these tall beings were here from ancient times. If ancient giants defy our concepts of evolution, might this be the very reason educational and governmental institutions might want to hide proof of ancient giants? They simply defy evolution and defy the Bible. What is left then? A scenario that would upset man. Alien intervention. At least with evolution, we evolve to a more efficient state to survive in a natural cycle of life and scientific wonder, and at least with the Bible, we are made in God's image. But, how do we explain ourselves in the context of alien creators? An experiment. Nothing more. And experiments can be tinkered with at will. So, we are no longer in charge of our planet. We also do not earn a way into heaven for what we did while here, nor do we believe the earth to be an efficient designer by nature alone. In essence, our world is a sham.
So, perhaps we can explain alternate versions of man that did not survive, cryptids, and even Bigfoot to massive experiments on our planet, utilizing what was available here in this setting and given the climate and resources, so that a sustainable and intelligent, efficient and ideal survivor could remain to inherit the earth, and given the intelligence of their designers.
Now, if this were so, why? What is there to be gained by anthro-farming a planet? For knowledge of how to custom design a life form? Or because the goal is to form intelligent life on many planets? And, if so, who is giving them this directive? What is there to be gained? And, will there be a day of meeting our makers and advancing to a level in which we ourselves are anthro-farming other planets?
It may not be popular with religious, educational and governmental organizations for us to question the manufactured version of our history, but there will come a day when the citizens, with the brilliant minds and curious nature of their makers (whomever those makers might be) will rise up and demand an accurate accounting.
And, perhaps, that is what the makers await - the full use of our minds in spite of man's desire to be sheep and fit in and not buck the system.
After all, in the scifi movies, isn't it always the brilliant rebel who wins?