Life Does Not Progress Toward Complexity
Early in life’s history there were just single-celled bacteria, but now there are all these very complex animals. So surely there must be a predictable trend toward increasing complexity—right?
I certainly don’t deny that the most complex creature on Earth has tended to be more complex as time has progressed. But we are really looking at this in an odd way if we construe it as a trend. It is more of an expansion from the necessary simplicity of beginnings, rather than some necessary, predictable drive toward higher states of organization.
For chemical reasons, life originated right at the lower bound of its possible complexity. You do not begin with a lion; you begin with something really simple. And if you begin there, then there is no room below it for less complexity. If life is going to expand, it’s going to occasionally add more complexity—but this is just a general expansion. Every once in a while, at the only open end of the spectrum, you add something that is more complex.
But the modal organism on Earth, the most common organism on Earth, remains a simple prokaryotic cell. That has never changed in the history of life on Earth, and is as true now as it was when the first living creatures arose. The number of E. coli bacteria in your digestive tract right now is greater than the number of human beings that have ever lived. And bacteria are going to outlive us; they cannot be nuked to oblivion, and they can survive on a much warmer globe than we can.
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Stephen Jay Gould wrote a ridiculous amount of brilliant stuff. Wouldn’t it be handy to just chat with Gould for a while, and have him summarize some of his big ideas? Boom: The Individual in Darwin’s World. This slim book simply records Gould’s brief “Second Edinburgh Medal Address.”
But as Gould warns inside the cover, “written and spoken English are different languages, and that the latter does not translate well into the former.” And the book has some typographical quirks to boot. So above I polished what you can read in its original form below:
First of all on the question of increasing complexity, you know people will say when I talk about this subject, ‘Look, you’re not being fair, you’re worrying something to death. Surely you don’t deny that early in life’s history there were just single celled creatures on a bacterial level of organization and now there are all these very complex things. So surely there must be a predictable trend in increasing complexity.’ I do not want to be a curmudgeon, yet I would urge a different view about the nature of complexity and the history of life. While not denying that the most complex creature on Earth has tended to be more complex through time, we are really looking at it in an odd way because it is more an expansion from the necessary simplicity of beginnings rather than a necessary predictable drive towards higher states of organization. Life for chemical reasons originated right at the lower bound of its conceivable preservable complexity. You cannot begin with a lion; you begin with something really simple, some chemical precursor. And if you begin there, there is no room below it for less complexity. If life is going to expand it’s going to occasionally add more complexity, and there is a drive in that direction; it is just a general expansion. Every once in a while, at the only end open, you add something that is more complex, but the modal organism on Earth, the most common organism on Earth, remains a simple prokaryotic cell, a bacterial level of organization. That has never changed in the history of life on Earth. It is as true now as it was when the first living creatures arose. There are more E.coli bacteria in the digestive tract of every one in this room than there have ever been human beings on Earth. [Hm, does Gould mean the digestive tracts of all the people in the room added together? Or the digestive tract of each person in the room, individually? I translated to the latter above, but if you can tell me whether that is the correct reading or not, please do! I can’t find the relevant figure of E. coli in a single human gut.] And those bacteria are going to outlive us; they cannot be nuked to oblivion. The modal organism on Earth has never changed. So we look at complexity the wrong way because we are complex and we tend to see a drive in that direction. It is not; it is just an occasional expansion, asymmetric expansion into that domain.