Interstellar Travel - Possibilities and Human Physiology

It's everything. History, environment, language, society, and oh yes, DNA.Perhaps a way to bridge the gap between the home planet and a freshly seeded population of humans would be anthropomorphic androids trained to raise a new human generation and a vast library containing art, history, primers on human society, etc.

We have previously written about two vehicles called Helios launched to study the Sun during the 1970s. Both of these probes attained maximum speeds of around 150,000 mph (250,000 km/h) at closest approach to the Sun in their highly elliptical orbits. Helios 2 was slightly faster than its twin craft, and this probe still holds the speed record as not only the fastest spacecraft but also the fastest manmade object in history.

I have serious doubts in our ability to colonize other planets. To colonize a planet we would need a large portion of the conditions we have on earth. Attempts at long term stays in sealed biospheres here on earth have failed. We are a relatively fragile species with specific needs in temperature, atmosphere, nutrition, pressure, radiation, emotional support, and G force. Even if we found a planet with many of earth's conditions, an absence of an important nutrient could easily result in failure. If you take a look at our population growth curve and pollution production trends, you will see that they are not sustainable in the long term. I think we will run out of resources or poison ourselves with our own waste before we develop the technologies for getting to habitable planets.
I could see the possibility of creating a space ship that spins to create centripital force simulating gravity for long term travel but the vastness of space makes the colonization of a planet a formidable task.
The other reason for my doubt is the absence of aliens.......