I can't get past the evidence that all large, warm-blooded animals today evolved to that size from mice-like ancestors (yes, even whales) in the last 64 million years.
Or was this guy suggesting that we DID come from adam and eve, but a billion years ago instead of 6 thousand?
The authors of that book don't put out too much theory, they mostly present facts. You can probably find summaries if you look. Electroplated gold jewelry buried in coal veins, humanlike bones hundreds of millions of years old, evidence of people coexisting with dinosaurs, footprints indicative of giant humanoids, and on and on and on.
The history of this planet is certainly not what most people think.
If we assume that no matter can travel backwards through time, or faster than the speed of light, (which so far is 99.999999999999% proven true) then every time they undertake a multi-light-year journey they'd be saying goodbye forever to everything they'd ever known. (The first Ender's Game trilogy covered this in great depth.)
You're assuming a lot about both physics and et.
Hyperspacial math predicts that matter can travel through time depending on where you are in hyperspace because as moxie said time is relative, both to space itself and to the number of spacial dimensions your reality contains (in our case three). It's really not right to think about time as forward and backward because
it's not linear.
And science proved long ago that things move faster than the speed of light. Even quantum mechanics, which is now almost a century old, shows that entangled subatomic particles can sense and respond to one another almost instantaneously over vast distances.
Moreover, if et has had more time and/or better luck than us, they may have mastered scientific principles that allow them to manipulate three dimensional space by using
energy from the vacuum or any number of other proposed megahuge energy generation techniques.
And as jenzkc said they may live for thousands of years or live indefinitely. This too would require advanced scientific knowledge of
biology and
programming but it is not at all out of the realm of possibility.
et may actually exist in higher dimensional space and interact with our three dimensional reality with no trouble at all. Who knows.
Long story short if et is here they're certainly not playing by the same rules we are.
Worth a browse if you're interested in this kind of stuff.
The Disclosure Project