ECAL session notes: Historical and Philosophical Perspectives on Artificial Life

What follow is a very slightly cleaned up version of the notes I took during the first ISAL summer school session at ECAL 2017. Note that this is very rough, I was just reviewing my notes and thought I may as well put them into a post format at the same time to revisit later. Apologies for any typos or other mistakes.

Historical and Philosophical Perspectives on Artificial Life

Mark A. Bedau, Reed College

Artificial Life

Artificial life enables us to learn fundamental properties of living systems by synthesizing them in artificial media

Kinds of alife:

Historical Roots

Why life is special:

Fundamental properties of life:

“Life deserves our scrutiny more than you might think if you just take some biology classes”

Birth of artificial life:

Historical roots: Reproduce and study key capacity of living systems in simple formal models.

Before the above conference, others made importnat advances the field grew out of; they are the “founding grandfathers” of the field:

Artificial life and complex systems

The field of artificial life today is connected with the study of complex systems.

Key elements:

It is extremely hard to understand complex systems by analyzing them; behaviour is dependent on interactions. The main practical way to study this is to build it, then step back and observe.

A grand challenge in artificial life

There appears to be a trend with all life - qualitative complexity. Complex organisms become more complex over time. Example:

As time goes on, complexity in life has increased. How? Why? What explains the above trend?

Perspective 1:

Deep law of nature?

When organized energy streams down onto earth, much of it simply turns into disorder. However, something else also happens…there are processes of organization rather than disorganization.

Perspective 2:

Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of higher animals, directly follows. There is grandeur in this view of life, with its several powers, being originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.

So haven’t we already explained this?! I learned about natural selection in middle school!

Before we start, some terms:

Arrow of complexity hypothesis

Evolution inherently creates increasingly complex adaptive organizations

The arrow of complexity is a robust regularity. It has constraints and exceptions, and is not accidental. No mechanism is specified.

Testing the arrow of complexity hypothesis

According to Stephen Jay Gould in “Wonderful Life”, all we have to do is “replay the tape of life”:

This would be an excellent test if we could actually do it.

Gould’s final analysis:

He concluded that there is no reason to think things would get more and more complex because no laws govern contingent processes.

The speaker’s diagnosis is that Gould did not actually replay the tape of life - he just thought about it. The second law of thermodynamics is highly contingent in itself and yet there is a law. There is a difference between imagining replaying the tape and actually replaying the tape

Dan Dennett’s analysis - Darwin’s Dangerous Idea

forced move: one obviously really good move; you are not physically forced to make it, but are “forced” by good chess playing because it is obviously the best move.

Problems with this:

Dennett thinks evolution is always going to create something that is more complex because it is a “forced move” (eg intelligence)

Speaker’s diagnosis: Dennett did not replay the tape, either. Like Gould, he just sat and thought about it a whole lot.

So - most people are just sitting in their office imagining replaying the tape, they are not replaying the tape.

How to actually replay the tape

“Put your model where your mouth is”

Gould and Dennett told a nice story, but they did not try to independently verify it. Without such a model, it is hard to see how you will get past verbal wars and stories.

Some models!

Diffusion model

This model has species with some complexity, and there is some process by which once in a while a species will give birth to a new species and go extinct.

Life starts off being very basic. Randomly choose if new species is more or less complex than the previous species. There is some chance of species going extinct.

Whether a species becomes less or more complex is random - there is no assumption of a forced move.

Results of the model: complexity does increase. The model vindicates the arrow of complexity hypothesis

Issues with this model:

How NOT to beg the hard questions

What we want in a model:

Example: Tierra

Tierra is close to the above. It takes computer memory & puts in a program created by hand that copies itself; one ancestor at gen0, the rest of the memory is empty. The program runs for a while and eventually copies itself. Eventually whole memory fills up.

Some features:

Some programs developed into “parasites”. They were shorter than others and could not copy themselves on their own. But if they were next to another organism that does have copy instructions, they could use that organism to copy themselves. So they’ve thrown away many of their instructions because they do not need them. They end up reproducing faster because they are less complex. When these parasites start becoming too successful, they actually begin dying out as there end up being fewer hosts with copy functions to take advantage of. And so the model goes back and forth between host and parasite dominance.

Tierra complexity is NOT just nominal

But does this confirm the arrow of complexity hypotehsis?

Lesson from Tierra:

No - Tierra didn’t quite confirm the arrow of complexity hypothesis.

The following are not by themselves sufficient to produce the arrow. Variations of them may be, but not simply their existence:

Darwin thought he proved the arrow via natural selection, but in the above model it’s not true! Natural selection is clearly not sufficient.

This remains one of the grand challenges in artificial life.

© - 2021 · Liza Shulyayeva ·