Animal and Fungus, Neurons the Difference

A Brief History of Intelligence is written by an AI engineer who studied the brain! So why did Max Bennett study the brain?

“The relations between AI and the brain goes both ways, while the brain can surely teach us about how to create artificial humanlike intelligence, AI can also teach us about the brain.”

He clarifies early: it is the human brain he is referring to, not brains in general. He starts from the beginning, from the evolution of neurons.

 

Fungus. It is closer to animals than plants. How? Because fungus cannot do photosynthesis; it takes in food and oxygen. Yet one lineage (animals) went on to develop brains whereas the other (fungi) didn’t. Why the difference?

 

Well, animals and fungi adopted different strategies for food – animals kill (plants or other animals) and then digest food inside themselves. Fungi wait for things to die and then digest them outside their body. Fungi use a spray-and-pray approach – they spray trillions of singled cells spores that float randomly. By luck, some of them will fall onto something dead. At which point, they start growing and start digesting the dead thing they started on.

 

Animals, on the other hand, take targeted actions to find food, they don’t move randomly hoping to stumble upon food. How do they do that? Thanks to the development of neurons in an ancient common ancestor of all animals. What did these neurons enable? They transferred information signals from receptors (or sensors) at the tips of the animal and transferred control signals to specific parts to relax and contract. Note this does not require a brain. Even that setup (only neurons, no brain) is hugely advantageous:

“It was the first time multicellular life sensed or moved… with speed and specificity.”

 

That then is the answer as to why only animals evolved neurons and eventually brains but not fungi. Only the former’s strategy required “fast and specific reflexes” – there was no evolutionary benefit for fungi in having neurons.