Sunday, January 15, 2012

Biological Revolutions of the Mind: An animal perspective.

(Picture from here.)

I've been thinking about the long view recently. Specifically, the age of life on this planet. Wikipedia's timeline of evolution is interesting but it compresses as it approaches us, in effect giving the same weight of the rise of complex cells to the rise of insects. This tends to trivialize the magnitude of complex cells.

I think we can consider a few points in the timeline as truly revolutionary:
  1. Abiogenesis revolution: the rise of living systems. Most of these are likely extinct.
  2. Prokaryotic revolution: bacteria and the like. About 3.8 billion years ago.
  3. Eukaryotic revolution: complex cells such as found in amoebas and human beings. Say, 2 billion years ago
  4. Multicellular life: About 1 billion years ago.
  5. Neurozoan revolution: Anything with a nervous system. This allows integrated system response to local stimulation. Somewhere between 1 billion and 600 million years ago.
  6. Cognozoan revolution: Centralized response driven life forms. Life forms with brains or central nervous systems (CNS.) Say 600 million years ago.
Neurozoan appears to be the invention of John Opie (2010.) Lots of animals have nervous systems and no brain-- hydras, for example.

Cognozoan is my own. Do you like it?

I do not use the term "revolution" lightly. While nothing really compares in scale to the abiogenesis revolution, each of these so-called revolutions changed the landscape of earth. Once we had prokaryotes we had the ability have true inheritance via DNA and variability in metabolism. We got photosynthesis and an oxygen atmosphere. Once we had eucaryotes we could have fungi-- which pretty much created something called "soil." All complex life forms from trees to sea anemones are multicellular. I suspect the roles of predator and prey, as we know them, originated here.

Neurozoans: all free living animals. Period. Full stop. End of story.

Once we introduce cognozoans, we have abstract behavior. Mating dances. Specialized predator/prey strategies. Fish. Crabs. Beetles. Starfish. Squids. Anything with a CNS. Most animals past the size of mesozoans have a brain. One could venture a guess that a central processing system is required beyond a certain level of behavioral complexity.

While this is an animal centric perspective I may be addressing some plant concerns as well.

I'm going to be going over these revolutions in the next few weeks and talking about them one at a time. Each of them is worth a blog entry of their own.

This is going to be fun.

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