Adaptive landscapes: A case study of metaphors, models, and synthesis in evolutionary biology

Adaptive landscapes: A case study of metaphors,
models, and synthesis in evolutionary biology
Emanuele Serrelli

Final discussion, XXIII cycle, January 2011
PhD School in Human Sciences
University of Milano Bicocca
Coordinator: prof. Ottavia Albanese
Advisor: prof. Dietelmo Pievani

1

Emanuele Serrelli


Introduction 1


cf. I.2.2 2


• Adaptive landscapes as a case of
scientific metaphor

cf. I.2.2 2


scientific metaphor

• Metaphor: nature and role in science

cf. I.2.2 2


scientific metaphor

• Metaphor: nature and role in science

‣ Consideration of the historical-
scientific context of its spreading: the
Modern Synthesis

cf. I.2.2 2


• The Modern Synthesis (MS):

1. a two-steps process (1910s-1930s)
central in shaping today’s evolutionary
biology;

2. its essence is communication among
separate fields (e.g. paleontology, Ernst Mayr (1904-2005)
theoretical and experimental genetics, Wikimedia Commons & PLOS Biology
morphology, zoology, botanics and so
on).

cf. I.3.2 3


Mayr’s view of MS pbs.org

paleontology
«...to give a grand sense of unity George Gaylord Simpson pbs.org
embracing genes, phenotypes
with their adaptations to different
environments, speciations, micro experimental genetics
and macroevolution, singular Theodosius Dobzhansky
episodes and the general pattern
of evolution» (p. 208).
ornithology, the naturalists
Ernst Mayr
sciencemag.org

theoretical genetics evolutionary theory skeptic.com

Sewall Wright Julian Huxley

...
cf. I.3.2 huxley.net 4


Mayr’s view of MS pbs.org

paleontology
George Gaylord Simpson pbs.org

experimental genetics
Theodosius Dobzhansky

ornithology, the naturalists
Ernst Mayr
sciencemag.org

theoretical genetics evolutionary theory skeptic.com

Sewall Wright Julian Huxley

...
cf. I.3.2 huxley.net 5


cf. I.3 6


• Introducing the idea of a migrant
metaphor:

cf. I.3 6


metaphor:

• NOT a “one-shot”, all-inclusive
metaphor of evolution;

cf. I.3 6


metaphor:


• NOT a “ready-to-use” universal,
context-independent tool;

cf. I.3 6


metaphor:


• NOT a “ready-to-use” universal,
context-independent tool;

• the migrant metaphor is found in
different fields of biology, but declined
differently in each.

cf. I.3 6


George Gaylord Simpson (1944)
Theodosius Dobzhansky (1937)
Tempo and Mode in Evolution
Genetics and the Origin of Species paleontology

cf. I.2.1, Fig. I.2 p. 9 - I.2.2, Fig. I.3 p. 17 - I.2.4 7


cf. I.1.3 - I.1.1 - I.1.2 8


• Three common ideas to adaptive landscapes:

cf. I.1.3 - I.1.1 - I.1.2 8



• “Higher is better” - altitude corresponds
to better solutions (peaks), and worst
possibilities are in valleys;

cf. I.1.3 - I.1.1 - I.1.2 8




• “better” and “worst” are relative to a
given environment which is not
represented in the diagram but influences
its structure;

cf. I.1.3 - I.1.1 - I.1.2 8




represented in the diagram but influences
its structure;

• landscape is the whole set of possibilities
for an evolving entity, and evolution is
conceived as the realization of
potentialities through time.

cf. I.1.3 - I.1.1 - I.1.2 8




represented in the diagram but influences Population adaptation as “climbing”
its structure;

• landscape is the whole set of possibilities
for an evolving entity, and evolution is
conceived as the realization of
potentialities through time.

cf. I.1.3 - I.1.1 - I.1.2 8


cf. I.3.3 9


• If MS was the building of a common
language among separate fields - as
opposed to an extension of mathematical
models of population genetics - here we can
see an important role for the adaptive
landscape metaphor as:

cf. I.3.3 9



• a figure of speech, generator of common
language (peak, valley, ruggedness etc.);

cf. I.3.3 9




• a migrant metaphor (µεταϕοσά, “to
carry over”, “to trasfer from”).

cf. I.3.3 9




• a migrant metaphor (µεταϕοσά, “to
carry over”, “to trasfer from”).

• An clue of the metaphor’s communicational
effectiveness: Dawkins (1996)

cf. I.3.3 9

cf. I.2.3,
Fig. I.6 p. 28,
I.2.4

froes.dds.nl

Adaptive landscapes: A case
study of metaphors, models, and Richard Dawkins (1996)
synthesis in evolutionary biology Climbing Mount Improbable
10

cf. I.4

nimbios.org

Adaptive landscapes: A case
study of metaphors, models, and Sergey Gavrilets (1997 sgg.)
synthesis in evolutionary biology Holey landscapes 11


Sewall Wright (1932)

Sergey Gavrilets (1997)

cf. I.5 - II.1, II.2 12


• Proposal to clarify the relationship between
holey and rugged landscapes it is necessary
to consider: the native (as opposed to
migrant) adaptive landscape metaphor.

Sewall Wright (1932)


cf. I.5 - II.1, II.2 12



• native theoretical context: Mendelian
population genetics (presented to
biologists of other specializations); Sewall Wright (1932)
conceived and proposed by Sewall
Wright in 1932 (paper “The roles of
mutation, inbreeding, crossbreeding and
selection in evolution” at the 6th
International Congress of Genetics);


cf. I.5 - II.1, II.2 12



• native theoretical context: Mendelian
population genetics (presented to
biologists of other specializations); Sewall Wright (1932)
conceived and proposed by Sewall
Wright in 1932 (paper “The roles of
mutation, inbreeding, crossbreeding and
selection in evolution” at the 6th
International Congress of Genetics);

• the same native context is shared by
holey landscapes.

cf. I.5 - II.1, II.2 12


cf. I.5, Fig. I.8 p. 63 13


• I proposed:

• Adaptive landscapes, in their native context, are a metaphor already, but a
metaphor in a different sense:

cf. I.5, Fig. I.8 p. 63 13


• I proposed:


• Could this open to a more general reflection about the recursive nature of
knowledge (involving the migrant metaphor as well)?

cf. I.5, Fig. I.8 p. 63 13


• I proposed:


• Could this open to a more general reflection about the recursive nature of
knowledge (involving the migrant metaphor as well)?

• Holey and rugged landscapes are metaphors for some population genetics model.
Which one?

cf. I.5, Fig. I.8 p. 63 13

cf. II.1

• Which population genetic model(s) are adaptive
landscapes metaphors of? Unclear in literature. 14


Mendelian
population
(high dimensionality)

EPISTEMOLOGICAL
GAP
equations METAPHOR

adaptive
surface
cf. II.2.1-3, Figg. II.1-2 p. 78 - II.2.4 15

• Which model(s) are adaptive landscapes metaphors of?
Unclear in literature:

1. Analysis of the theoretical structure of population
genetics;

2. result: in its native context, adaptive landscape was
metaphor of a really fundamental formal object:
Mendelian population, i.e. a combination space provided
with fitness;

3. the space has too many dimensions to be treated directly
with mathematical equations (epistemological gap):

‣ I criticized many authors who considered landscapes
as a metaphor of “too complicated equations”;

‣ I analyzed how Wright probably did arrive to know
something about the combination space (intuition,
limited experience, and heuristics).

cf. II.2.1-3, Figg. II.1-2 p. 78 - II.2.4 16

cf. II.1,
Fig. II.3 p. 79,
Population genetics II.3

Mendelian Biometrical

• A further source of confusion in literature: what is to be
intended with “model”? 17

cf. II.1,
Fig. II.3 p. 79,


Many notions of models are
available


cf. II.1,
Fig. II.3 p. 79,


available

⇓


cf. II.1,
Fig. II.3 p. 79,


available

⇓
Variability in the semantic
extension of the term “model”


cf. II.1,
Fig. II.3 p. 79,


available

⇓

⇓


cf. II.1,
Fig. II.3 p. 79,


available

⇓

⇓
Need for a pragmatic approach
in philosophy of biology


Proposal: Term Kind of object Synonyms

Mendelian Model as «stable target of explanation», - Combination /
a pragmatically- population similar to model organisms in genetic / metric space
stated vocabulary experimental biology - Space

for debating (with fitness)

Mendelian Theoretical structure Wrightian population
adaptive
population genetics genetics (opposed to
landscapes. Fisherian or biometrical)

Population Dynamical system

Realized (N individual) subset of the

model

Function of time

Environment, Compressed self-evident truths

phenotypes, and

interactions among

them

Population genetics Equations of gene frequencies (one or Equations

equations few diallelic loci, frequency spectrums)

Landscape language Metaphorical verbal language, Includes peaks, valleys,

vocabulary to communicate features of ruggedness, ridges,

the model climbing etc.

Landscape models Combination spaces built on imitation of Landscape spaces,

Mendelian population. These models are combination spaces,

«stable targets of explanation» in their spaces

own right.

Adaptive surface 3D visualization - Fitness surface

- metaphorical in case of high- - Surface

dimensional spaces - Surface picture

- exact in case of low-dimensional spaces - Landscape picture
cf. Table II.1 p. 116 18
Table II.1. Pragmatically-stated vocabulary for the debate on adaptive landscapes.


cf. III.2 19

• Today’s landscape models:

cf. III.2 19


• surface is not essential;

cf. III.2 19



• they are combination spaces (thus similar to
Mendelian population) to which landscape
metaphorical language is applied;

cf. III.2 19




• they vary by:

cf. III.2 19




• they vary by:

‣ nature of factors which are combined;

cf. III.2 19




• they vary by:


‣ dimensionality;

cf. III.2 19




• they vary by:


‣ dimensionality;

‣ method of fitness assignment;

cf. III.2 19




• they vary by:


‣ dimensionality;

‣ method of fitness assignment;

‣ nature of dynamics.

cf. III.2 19

Mount Improbable
pbs.org
Richard Dawkins

paleontology


sciencemag.org

skeptic.com
theoretical genetics
Sewall Wright

cf. III.1 huxley.net 20

Mount Improbable
pbs.org
Richard Dawkins

paleontology

Very conservative,
but inconsistent
sciencemag.org

skeptic.com
Sewall Wright


Mount Improbable
pbs.org
Richard Dawkins

paleontology

Innovative (phenotypic),
consistent experimental genetics
Very conservative,
but inconsistent
sciencemag.org

skeptic.com
Sewall Wright


Mount Improbable
pbs.org
Richard Dawkins

Rhetorical, paleontology
abstracting George Gaylord Simpson pbs.org

Innovative (phenotypic),
consistent experimental genetics
Very conservative,
but inconsistent
sciencemag.org

skeptic.com
Sewall Wright



Model
= Mendelian population
(= high-dimensional combination space)
Research
interest:
NEUTRAL CHANGE
Research
interest:
ADAPTATION

cf. III.2.3, III.3 21


Gavrilets (2004)

Research
interest:
SPECIATION Model
Research
interest:
NEUTRAL CHANGE
Research
interest:
ADAPTATION

cf. III.2.3, III.3 21


A patchwork of formal-
mathematical tools:
Gavrilets (2004)
Statistical analyses

Low-dimensional spaces

Equations of gene
frequencies

Research
interest:
SPECIATION Model
Research
interest:
NEUTRAL CHANGE
Research
interest:
ADAPTATION

cf. III.2.3, III.3 21

“Holey”
combination
A patchwork of formal- spaces
mathematical tools:
Gavrilets (2004)


Equations of gene
frequencies

Research
interest:
SPECIATION Model
Research
interest:
NEUTRAL CHANGE
Research
interest:
ADAPTATION

cf. III.2.3, III.3 21

“Holey”
combination
mathematical tools:
Percolation
Gavrilets (2004) analysis


Equations of gene
frequencies

Research
interest:
SPECIATION Model
Research
interest:
NEUTRAL CHANGE
Research
interest:
ADAPTATION

cf. III.2.3, III.3 21

“Holey”
combination
mathematical tools:
Percolation
Gavrilets (2004) analysis
Statistical analyses Visual,
metaphorical
representation

Equations of gene
frequencies

Research
interest:
SPECIATION Model
Research
interest:
NEUTRAL CHANGE
Research
interest:
ADAPTATION

cf. III.2.3, III.3 21


cf. III.3.2 - III.3.3 22

• The landscape example (and particularly the analysis of
Gavrilets’s Fitness Landscapes and the Origin of Species, 2004)
shows:

cf. III.3.2 - III.3.3 22

shows:

• advancement of modeling is not trivially a better and
more complete description of the world;

cf. III.3.2 - III.3.3 22

shows:


• in population genetics there is a fundamental model, and
a “patchwork” of interrelated tools that

cf. III.3.2 - III.3.3 22

shows:



‣ increase our knowledge of the model;

cf. III.3.2 - III.3.3 22

shows:




‣ make it suitable to be a model for phenomena of
interest (adaptation? speciation?), and perhaps not
others.

cf. III.3.2 - III.3.3 22

shows:




others.

• interests vary and change through time;

cf. III.3.2 - III.3.3 22

shows:




others.

• interests vary and change through time;

• relationships in the patchwork (e.g. between “holey and
rugged landscapes”) are to be considered carefully.

cf. III.3.2 - III.3.3 22


Massimo Pigliucci (2008, 2010)
friendlyatheist.com

cf. IV.2.1, IV.2.2 - IV.1 23

• Pigliucci’s contemporary interests (worries):

friendlyatheist.com

cf. IV.2.1, IV.2.2 - IV.1 23


• modeling phenotypes together with genotypes (cf.
G➝P map);

friendlyatheist.com

cf. IV.2.1, IV.2.2 - IV.1 23


G➝P map);

• evolvability (sensu Wagner & Altenberg 1996) = the
ability of a population to respond to selection;

friendlyatheist.com

cf. IV.2.1, IV.2.2 - IV.1 23


G➝P map);


• general perspective: Extended Evolutionary Synthesis.

friendlyatheist.com

cf. IV.2.1, IV.2.2 - IV.1 23


G➝P map);



• Pitfalls of his analysis of adaptive landscapes (2008): Massimo Pigliucci (2008, 2010)
friendlyatheist.com

cf. IV.2.1, IV.2.2 - IV.1 23


G➝P map);



friendlyatheist.com

• emphasizing too much what is (legitimately) missing;

cf. IV.2.1, IV.2.2 - IV.1 23


G➝P map);



friendlyatheist.com


• forced interpretations of past research questions as
forerunners;

cf. IV.2.1, IV.2.2 - IV.1 23


G➝P map);



friendlyatheist.com


• forced interpretations of past research questions as
forerunners;

• historical-epistemological conflations.

cf. IV.2.1, IV.2.2 - IV.1 23


Sidlauskas et al. 2010 (NESCENT)

cf. IV.1, IV.2.3 - Conclusions pp. 213 sgg. 24

• Challenges for the Extended Synthesis (synthesis seen
as an object):



as an object):

• having a theoretical structure;



as an object):


• give a proper position, in that structure, to models
and tools.



as an object):


and tools.

• Another interpretation (by NESCENT): synthesis as a
continuing process. Overcome fragmentation by:


as an object):


and tools.


• innovative (also visual) representations of
information;


as an object):


and tools.


information;

• common languages.


as an object):


and tools.


information;

• common languages.

• There’s clearly a role for landscapes, and for
philosophy.


Emanuele Serrelli


25

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