Introduction to Complexity Science - PowerPoint PPT Presentation

1 / 20
About This Presentation
Title:

Introduction to Complexity Science

Description:

Introduction to Complexity Science – PowerPoint PPT presentation

Number of Views:89
Avg rating:3.0/5.0
Slides: 21
Provided by: Set450
Category:

less

Transcript and Presenter's Notes

Title: Introduction to Complexity Science


1
Introduction toComplexity Science
Adaptation
2
Adaptive Complexity
?
?
?
3
Terms
Adaptive 1. Flexible, plastic capable of
changing 2. Fit for purpose evolutionarily
adaptive Adaptation 1. An evolved trait 2. The
process that generates adaptations 3. Also
process of change in, e.g., the eye Adapt,
Adaption To change purposefully cf
chameleon Adapted Altered in order to response
4
Complex Adaptive Systems
  • Complex adaptive systems come in many forms
  • Evolutionary, Neural, Cultural, Linguistic, etc.
  • Markets, Languages, Brains, etc.
  • Their hall-mark
  • without global co-ordination
  • organisation comes to reflect environment

5
Gaia
H our planet functions as a single organism
that maintains conditions necessary for its
survival
Gaia is not an organism, but an emergent
property of interaction among organisms. What
is the claim here? That genes bring about and
maintain global homeostasis?
6
Fallacies, Misconceptions, etc.
  • Since adaptive systems almost always combine
  • scale
  • connectivity
  • non-linear interactions
  • they are often complex adaptive systems.

Consequently, adaptive systems are extremely
subtle, and at times, counter-intuitive.
  • But they are
  • the most potent source of biological inspiration
  • extremely important in their own right

7
Units of Selection
We are survival machinesrobot vehicles blindly
programmed to preserve the selfish molecules
known as genes. This is a truth which still
fills me with astonishment. Though I have known
it for years, I never seem to get fully used to
it Richard Dawkins.
Why do we serve genes and not vice versa?
  • Because genes are replicators
  • longevity, fecundity and copying-fidelity
  • they, not us, persist across generations
  • changes to genes, not bodies, are copied
  • e.g., amputees do not give birth to amputees

8
Group Selectionist Thought
Dawkins work contributed to the debunking of
evolutionary explanations cast at the group level.
  • Ageing good for the herd, weeds out stragglers
  • Sex ratio efficient for pairing males females
  • Communication the exchange of information

It can be seductive to imagine a kind of
selective hierarchy. But higher selective
pressures are undercut by those below so genes
hold the trump card.
  • Groups
  • species
  • ecosystems
  • biosphere
  • organism!

9
Game Theory
Game theory suggests that global altruism is
unlikely to survive individual selfish interests
  • Tragedy of the Commons
  • a little restraint ensures a common resource for
    all
  • Prisoners Dilemma
  • if both prisoners resist temptation, both go free
  • Hawk-Dove game
  • if all play Dove, resources are shared
    non-violently

In each game, short-termist, individualist,
gene-eyed behaviour destroys fragile
mutualism. Unfortunately such games are
everywhere.
10
Progress
Short-termist, individualistic, gene-eyed
evolution seems progressive a march from monad
to man.
11
Evolution ? Optimization
But, why would a blind process of random change
selection inexorably drive towards anything?
12
Arms Races
Dawkins Krebs suggested that arms races
between coevolving species might drive progress.
  • But arms races do not spiral upwards.
  • And surely this is short-term stuff?
  • Is it, in fact, just adaptation?

More significant, are major innovations cells,
sex, multi-cellularity, sociality, even
language Might evolution never be the same
again after each major transition.
13
Major Transitions
For Dawkins, major transitions are watershed
events in the history of life. They bring about
new ways of being adaptive, new opportunities...
boosting evolution itself in
ways that seem entitled to
the label progressive Once brought
about, such transitions
may be difficult
(though not impossible) to reverse, conferring a
one-way ratchet of of progressive innovation.
14
Fitness Landscapes
Central to much reasoning about adaptation is an
iconic visual metaphor the fitness landscape.
?
  • dimensionality
  • neutrality
  • locality
  • passivity
  • objectivity

15
Open-Ended Evolution
What features must be present in a system if it
is to lead to indefinitely continuing
evolutionary change? Maynard Smith.
  • Since adaptation is a response to environmental
    pressures, some authors suggest that an
    ever-changing environment may be such a feature.
  • E.g., Co-evolution amongst species
  • Additionally, the replicators involved will
    necessarily need to be able to build more
    complicated (complex?) replicators.
  • However, still an open(-ended?) question

16
Apparent Design ? Evolution
Natural selection is the only known mechanism
capable of effecting the appearance of design.
In On Growth and Form DArcy Thompson argues that
honeycomb structure arises for the same reasons
as spherical bubbles.
What other structures, behaviours, organisations
can be explained in this way?
17
Constraints vs. Opportunities
Physics and chemistry, then, define, populate and
structure the space of possible adaptations.
  • Often thought of as constraints on evolution.
  • But it is as accurate to use enabling language.
  • The morphospace of available forms seeds
    natural selection with self-organising
    structures.
  • Is morphospace sparse or densely populated?
  • Your answer to this question fixes where you sit
    on the self-organisation vs. selection debate.

18
Self-Organization vs. Selection
We stand in the need of a new conceptual
framework that allow us to understand an
evolutionary process in which self-organization,
selection and historical accident find their
natural places with one another. Kauffman.
Ultra-Darwinists believe that it is practical
to neglect morphospace considerations. An
opposite position holds that understanding
natural complexity is largely a matter of
grasping the nature of self-organisation.
19
Evolution To The Edge of Chaos
A system cannot exhibit adaptation (via natural
selection) if it tends to either fixity or
disorder.
Stasis/Fixity
Disorder/Flux
Complexity
If possible, systems will evolve such that they
sit between fixity and flux at the edge of
chaos.
  • This regime has some interesting properties
  • complex patterns, robustness, efficiency
  • scale-invariant behaviour
  • but not just adaptive systems

20
Power Laws
What unites those systems that exhibit power
laws?
Is this due to self-organised criticality? Observe
d in distributions of earthquakes, firm GDP
growth, evolutionary extinction, internet traffic
structure, epidemics, heart arrhythmias How
long will it be before the power law has as
central a role in science as the normal curve?
Write a Comment
User Comments (0)
About PowerShow.com