Humans could be Martians says Brian Cox

Could life pre-date Earth? A renowned physicist said this weekend that we know far less than we think – and life on Earth could have originated elsewhere, perhaps on Mars. For millennia, we humans have wondered where we might have come from. The Abrahamic religions proposed that we were created six days after the rest of the world. In ancient Chinese mythology, we originated from mites on the corpse of Pangu the demigod. One thing all these stories had in common was their conviction that life developed on Earth. But now, this age-old belief is being challenged by new scientific evidence. Physicist Brian Cox is the latest prominent scientist to suggest the first microbes on Earth came here from Mars. Organic molecules exist more or less everywhere in the universe. But we still do not know how some of these fused together to form single-celled organisms. Scientists increasingly believe the early Earth had too much water for the first microbes to flourish. They would have benefited most from shallow waters. And this is exactly the environment they would have found on Mars. Then, around 3.7 billion years ago, everything changed. Mars became a dry environment with no running water. On Earth, the oceans fell away, creating land and shallow waters. So, just as Mars became inhospitable, Earth was turning into the best neighbourhood in the solar system. If a few of the more complex single-celled organisms on Mars were able to hitch a ride on an asteroid, they could have made it to Earth. For many, this is the most exciting thing about science: big shifts that change our whole way of looking at the world. The same thing is happening in evolutionary biology. Since the 19th Century, all scientists have agreed that life evolves gradually and continuously.  But now some scientists are challenging this. They think evolution happens quickly in short bursts, followed by long periods in which species do not change much at all. Could life pre-date Earth? Life on Mars Yes: The chances of life emerging in two different places are astronomical. If we do discover life of any kind on Mars, it will be compelling evidence that all life on Earth started on the Red Planet and made its way over.  No: Single-celled life would have struggled to survive a trip on an asteroid. And there is no reason why the Earth could not have provided the right conditions for life to develop once land started to emerge. Or… There is still much we do not know about how early cells worked. We do not know if they were anything like the cells we have today. More study is needed before we can be sure where life emerged. KeywordsOrganic molecules - Compounds that contain carbon-hydrogen bonds and are essential for life.