That's the great thing about science- there is no end. And while it would be great if we could go back in time to the beginning of the universe, we can't. Because we will never see that occur, there is no such thing as "proof" (in the colloquial sense) for any argument. In terms of the scientific definition of proof, we have already proved evolution. To quote Sean Carroll:

I would say that "proof" is the most widely misunderstood concept in all of science. It has a technical definition (a logical demonstration that certain conclusions follow from certain assumptions) that is strongly at odds with how it is used in casual conversation, which is closer to simply "strong evidence for something." There is a mismatch between how scientists talk and what people hear because scientists tend to have the stronger definition in mind. And by that definition, science never proves anything! So when we are asked "What is your proof that we evolved from other species?" or "Can you really prove that climate change is caused by human activity?" we tend to hem and haw rather than simply saying "Of course we can." The fact that science never really proves anything, but simply creates more and more reliable and comprehensive theories of the world that nevertheless are always subject to update and improvement, is one of the key aspects of why science is so successful."

PS. CyberLN is right- atheism isn't a faith and if you call it one, most atheists will laugh and/or be very offended. Faith implies a religion, with traditions and, generally, deities. The only thing that atheists have in common is the lack of all of that. Some comparisons I've heard that might help get the concept across:

- Atheism is a religion like "off" is a TV channel.
- Atheism is a religion like "bald" is a hair color.
- Atheism is a religion like "not collecting stamps" is a hobby.

We act as a community because we're marginalized and often want to join together with people who think like we do when the rest of the world says we're not right and, more than that, innately bad people. But, similar things could be said for various other groups in the US, like political parties, some unions, fraternities, clubs, and activist groups, all of which are not religious but share ideologies.

I think the word "Faith" and "Beleive" have been dominated by spiritualism. You see, according to the definition of "Faith" is to put merit or trust in a claim to be true, just as "Believe" is to accept or regard something as truthful. Howeve, both terms have sorta been high-jacked by religious spiritual movements, where people both have "faith" or "believe" in a spiritual doctrine or diety, it's power, divinity, ect... Usually comes about through some spiritual, ritualistic, or otherwise religious occurences.

However, when an atheist uses the phrase "I believe.." it's not a spiritual belief. It's that through what we learn from the sciences. It's what we learn through our day to day experiences with the world. It's actually very mundane, fact driven, testable, repeatable processes that make sense according to the vast inter-relatedness of all we know about our world and universe, and how it operates without fail. I think you will find that yes, atheists do have beleifs, or ideas we give merit to based on fact and observation, but it's not like your beliefs at all. There's much less miracles, ghosts, jewish zombies, men who get stronger as their hair grows, Arabs riding a donkey into the sky, talking to to any god, angels smiting cities, demons, armegeddon, retribution, reincarnation, sin, talking snakes, giants, trolls, gods,... I could go on but, the list of what we don't have in our belief structure would be outrageous. Here's what we do believe in: How people think (psychology) and how people interact (Sociology) and how the world universe acts (Various Sciences).