It is amusing to me that you still cling to this argument, even though it has been explained many times on this forum that this is not true. I think "stuck" accurately describes your state of mind. To recap the many many many many posts on this subject, and to add just one more for the heck of it:
1. What is "higher" life form? Without a definition, this argument is meaningless. I wouldn't necessarily agree that humans are the most intelligent creatures even on this planet. Again, without definitions, adjectives like "highest" and "chief intelligence" are completely meaningless.
2. None of the atheists I know deny the possibility of life on other planets that would probably be very different than us if they existed.
3. The question of whether different life forms exist on other planets is completely irrelevant to the question of whether there is a god or not, unless your religion is scientology. If your religion is scientology, you have much bigger problems.
4. To be an atheist, all you have to do is acknowledge that we don't know. We don't know how everything came to be or what happened in "the begining" or even whether there was a begining at all.