People with supernatural beliefs typically deny that our brains can be explained naturalistically, but the more scientists study biology and the brain, the more they understand. Recently it was discovered that some of the basic chemistry that allows our brains to operate existed long before brains existed -- or even animals existed.
Choanoflagellates are aquatic organisms found in oceans and rivers around the globe. Being a single cell, they do not have nerves, yet the team found both proteins in the choanoflagellate Monosiga brevicollis, and the interaction between the two was the same as in neurons... These proteins are found in every nerve cell and control the release of the chemicals which neurons use to talk to each other, called neurotransmitters.
The finding is intriguing on its own, but much more significant when combined with a growing body of evidence that essential brain components evolved in choanoflagellates before multicellular life appeared.
And this year, Harold Zakon of the University of Texas at Austin and colleagues discovered that M. brevicollis has the same sodium channels that neurons use to pass electrical signals along their length ...Put together, these findings suggest that choanoflagellate cells have components for each of the three main functions of neurons: carrying electrical signals along their bodies, signalling to their neighbours with neurotransmitters, and receiving those signals.
Source: New Scientist, September 3, 2011
Choanoflagellates are our nearest single-celled relative, so a direct line can be traced between them an us. What's more, choanoflagellates sometimes gather together in colonies, causing them to act a bit like multi-cellular animals. Since multi-cellular life almost certainly arose out of single-celled organisms that bonded together in a permanent colony, choanoflagellates are an important area of study for understanding how and why we exist the way we do.
Also important is the fact that Evolution Deniers frequently argue that systems like our brains are too "complex" to develop naturally out of simpler parts and processes. Here, though, we see exactly what Evolution Deniers insist cannot exist: simpler forms of basic brain systems that have become complex in us -- and we're seeing it all in a form of life that is directly related to us, too.
Each of these systems do different things for choanoflagellates than they do for us, but when brought together they can do completely new and different things. And that's exactly how we would expect something like a brain to develop naturally in a context where evolution occurs.
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