Solving the problems of life traveling to the next star in the Milky Way, are as far away to us as Jets were to the Wright Brothers. It's not just distance that's the problem.
It's getting a life form 100% adapted to life on Earth to go the distance and survive. Life needs air, food, water, etc. This without the problems of fuel. The environment on the space ship has to good built to suit a life form that has adapted over many millions of years to live on the Earth. Gravity is a major problem. Spend 6 weeks in bed and see how well you can walk when you get out of bed. 6 months in zero gravity will waste muscles, 6 years, no one has a solution to that yet. Suspended animation doesn't solve the problem. That's for movies.
And when the traveler arrives on the distant planet, if the environment isn't 100% suitable to a life form developed on Earth. It will need a huge space suit to waddle around in. Assuming we can figure out how to make a suit in a way to suit an atmosphere we have no clue about.
H.G.Wells had it figured out in book War of the Worlds. The invaders couldn't live on Earth even though they were clearly advanced way beyond our civilisation.
The fact that a relative to the Monkey is now supreme on Earth is all by chance. If dinosaurs hadn't of died out when a meteor had hit the Earth, mammals would never of been the allowed to develop. The dominant life form might be a descendent of the T.Rex for all we know. Scientists are still trying to work out why Man is bipedal, as we are the only mammal that is and it's clearly inferior to four legs. Unless you have wings.
The theories they had about looking over the grass to see predators has been discarded now they have found an earlier humanoid who lived in a jungle where the ability to climb trees would of been better. Still not very good to see a lion 500 yards away if he can out run you in a flash.
All these fine points are what made us and will apply to life forms on other planets. Men in Black portray alien life form better than most people who say they came here or have met one. Yet people insist aliens they propose are bipedal, 2 arms, 2, legs, head, etc.
