Over the past two million years or so, we have evolved to the point where we've reached about the maximum possible size of our brains. As anthropologists may argue, our brain capacities may actually be getting smaller, and all for a simple reason – the anatomical difficulties that birthing a large-headed child poses. For a while in human history, childbirth was the leading cause of death for women, so evolution will not opt to work on the size of our skulls in the future, for obvious reasons. Now, the question is, where does that leave us?

It has become apparent that, for the last 5,000 years or so, our brains have been constantly getting smaller. Other human species that lived before us had larger brains, but evolution weeded those out, for the very same reason we mentioned earlier. With more and more fossils being constantly discovered, our history becomes clearer, allowing scientists to piece together our evolutionary past. There are numerous theories about what we will come to be over the millennia. Some of the ideas are inspired from science-fiction novels, while others are proposed by respected academicians. But some of them are simply unfeasible, and without any merit.

For instance, there is a belief that humans will grow to sport an impressive brain, similar to the ones currently depicted in the representations of “little green men,” or extraterrestrials. But that is, of course, impossible. “If you've ever gone through a childbirth or witnessed one, we're already anatomically right on the edge of how big our heads can go – our big brains have already caused extreme problems in childbirth, and if we had bigger and bigger brains, that'd cause more mothers to die in childbirth, so evolution would select against that,” University of Washington in Seattle (UWS) paleontologist Peter Ward explains.

Another idea is that the human race would separate into two distinct species, one of tall, slim, beautiful and highly intelligent “superhumans,” and the other one made up of dim-witted, fat and sick individuals. But Ward strongly argues against the disappearance of intelligence. “Why would that happen? Are we like blind cavefish? After we get Google, do we get stupider? Intelligence is coded on too many genes to just lose a trait like intelligence. That's not going to happen,” he explains.

“If you want to make a new species, you have to really separate populations out. If we're all holed up on Earth, I don't see new species emerging, unless of course we engineer one. However, if we get some populations to split off by sending them off to space colonies, where they might evolve under different environments, it's possible,” Ward concludes, quoted by LiveScience.