Complexicon: Selection

Dr. Paul Hooper talks about selection in complex systems!

Natural selection is a process
that causes adaptive characteristics

to become more common in any system
that meets three basic criteria.

1), there must be variation in some trait
or characteristic in the population.

2), traits tend to be inherited,
or passed on, when individuals reproduce.

And 3), variation in the trait is related to variation
in how much individuals will reproduce,

what we call differential reproduction.

So for selection you need variation,
inheritance, and differential reproduction.

This easily applies to plants, animals,
and the other organisms that reproduce using genes.

Let's say you have a bunch of single-cell bacteria
that normally feed on carbon

and you put them in a new environment
that has a lot of sulfur.

When would you expect selection
to favour the ability to feed on sulfur?

You would if, 1), there is variation among bacteria
in the ability to eat sulfur,

2), the offspring of sulfur-eating bacteria
also tend to eat sulfur,

And 3), bacteria that eat sulfur
tend to leave more offspring than those that can't.

In this example, offspring are probably similar to their parents
because they inherit genes from them.

But it turns out that selection occurs
in many types of systems, not just genetic ones.

Take stories. Some stories have features:
a good character, an interesting plot;

anything that makes them
more memorable than other stories.

So one, there's variance.

When people retell a story,
the version they tell

will usually have most of the same features
as the version they heard.
When people retell a story,
the version they tell

will usually have most of the same features
as the version they heard.

So 2), there's inheritance.

Finally, stories with features
that make them more memorable

tend to get remembered and re-told
more often than less memorable stories.

So 3), there's differential replication
or reproduction of stories.

So in this system, selection would cause
stories with more memorable features

to become relatively more common over time.

Keep in mind that selection isn't the only force
affecting the frequency of different traits in a population.

Innovation, mutation, and random processes
like drift are also important.

Selection isn't even the only process
that drives adaptation.

Individuals can adapt to new circumstances
by learning from experience, for example.

And there are, in fact, deep similarities
between the mathematics of natural selection

and other adaptive processes
like Trial and Error Learning and Bayesian Learning.

Understanding the role of selection
and other dynamical processes

in biological, social,
and technological systems

is some of the work that we do
here at the Santa Fe Institute.