Opinion:
JoeTheJuggler
My theory takes all the facts into account: when Noah built the Ark, the story handed down by word of mouth got a little garbled. There was actually a fleet of them (enough to hold all the animals as the Biblical record accurately states). One of them even had Bigfoot on it. That particular one got swept up in a Fortean, interplanetary river and crashed on Mars. That's why you see things like the mysterious plank (a timber from the Ark) and Bigfoot on Mars. This human skull was obviously one of Noah's relatives that commanded the Mars-bound Ark.