Evolution

The brain is an organ with over 500 million years of evolution behind it. It probably got started as integration centres in simple nerve nets — the early brainless nervous system, where clusters of neurons began pulling together the work of sensing and responding. From there, step by incremental step, the design built outward: the reptilian brain, the mammalian brain, the primate brain. Each stage added capabilities rather than replacing them. The human brain still uses mammalian and reptilian brain structures underneath everything else; evolution rarely throws working parts away.

Some of the most striking recent work is on C. elegans, a nematode whose nervous system, by the standards of anything larger, is almost a toy. Three hundred neurons. You can map every single one. And yet a University of Leeds study found behaviour in this tiny system that looks startlingly sophisticated. The neurons don’t only track what is happening in the present moment; they carry information about the recent past. They can flexibly remap what they encode — about thirty percent of behaviour-encoding neurons can take on new jobs depending on what the animal needs. Three hundred neurons doing what researchers a generation ago would have considered the province of much larger brains.

That matters because it suggests the core capabilities we associate with thinking — memory, flexibility, context-sensitivity — are not late evolutionary add-ons that appeared with primates. They are in the design from very early. What larger brains add is not a categorical leap but more of the same thing, at greater scale and with new patterns of connection. The human brain is a variation on a very old theme, played on a larger instrument.

The brain develops through association, creating concepts by connecting sensory signals into patterns that survive repetition. Language and culture then co-evolve with the brain, producing what is sometimes called a complex adaptive system: the brain shapes the culture, the culture shapes the brain, and the loop runs forward through generations. Neither side is the master. Each is partly the creation of the other.

In recent millennia, cultural evolution has accelerated dramatically. Writing, print, electronic communication — each threshold compresses the rate at which patterns can be shared and accumulated. At some point the pace of cultural change outruns the pace of physical change so thoroughly that mental evolution starts to decouple from biological evolution. What happens to a species when its thinking evolves faster than its bodies? That is, as far as I can tell, a live question for us right now.

None of this is a road to guaranteed paradise. The brain is old, it is powerful, and it is also a device that will cheerfully confirm your own biases for you all day long. But the combination of a brain that reconfigures itself in response to use, a culture that now accumulates knowledge at an unprecedented rate, and tools that can extend the thinking further still — that is a journey worth taking seriously. I am ready for it, excited to see how much of the shape of our future is still open.

This post is from an earlier moment in the walk (03/12/2024). For how this connects to the wider picture of evolutionary transitions, see Evolution.

This post is part of the preamble, about happening before SPLectrum saw the light of day.

Photo: Johannes Plenio / Unsplash