Short communication at CISEPS Annual Lecture May 6, 9:30am, University of Milano Bicocca, Milano (Italy), building U12, Also with: - Luca Cavalli Sforza "Critical periods of human evolution: interdisciplinarity helps for understanding" - Marcus Feldman, "On Models of Social Transmission: Rates of Evolution and Patterns of Diversity".

1. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
A Niche Construction Model with Reaction
Norms
Fabrizio Panebianco and Emanuele Serrelli
University of Milano - Bicocca
May 6, 2011
CISEPS ANNUAL REPORT

2. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
Cultural Evolution Project

3. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
Outline
• Niche construction
• as a neglected major biological process
• as modification and innovation of existing models
• Something missing in NC models: phenotypic plasticity
• NCRN model: a niche construction model with reaction
norm
• Basic and population NCRN Models
• NCRN, cultural evolution, and economical modeling
• First Formalization

4. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
Niche Construction: «the selection pressures to which an
organism is exposed exist partly as a consequence of the niche
constructing activities of past and present generations of
organisms»(Laland et al. (1996), p.294)

5. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization

6. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization

7. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
That the activities of organisms lead to environmental modifications, on
both on a local and global scale, can hardly be doubted; so much is
obvious to even the most casual observer of the natural world. . . . if
everyone agrees that niche-construction, i.e. organism-induced
modification of the environment, occurs, why does orthodox evolutionary
theory fail to take account of it? (Okasha 2005, p. 1).

8. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
• Laland KN, Odling-Smee FJ, Feldman MW (1996). On the
evolutionary consequences of niche construction. Journal of
Evolutionary Biology 9: 293-316.
• Laland KN, Odling-Smee FJ, Feldman MW (1999). The
evolutionary consequences of niche construction and its implications
for ecology. Proceedings of the National Academy of Sciences USA
96:10242- 47.
• NC models are modification of multiplicative model (two loci)
• Locus E (alleles E, e), Locus A (alleles A, a), Resources R
• Frequency in E influences R, R influences A’s contribution to fitness
The analysis confirms that niche construction can be a potent
evolutionary agent by generating selection that leads to the fixation of
otherwise deleterious alleles, supporting stable polymorphisms where none
are expected, eliminating what would otherwise be stable polymorphisms,
and generating unusual evolutionary dynamics. Even small amounts of
niche construction, or niche construction that only weakly affects
resource dynamics, can significantly alter both ecological and
evolutionary patterns. (Laland et al. 1999, p. 10242).

9. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
• Laland KN, Odling-Smee FJ, Feldman MW (1996). On the
evolutionary consequences of niche construction. Journal of
Evolutionary Biology 9: 293-316.
• Laland KN, Odling-Smee FJ, Feldman MW (1999). The
evolutionary consequences of niche construction and its implications
for ecology. Proceedings of the National Academy of Sciences USA
96:10242- 47.
• NC models are modification of multiplicative model (two loci)
• Locus E (alleles E, e), Locus A (alleles A, a), Resources R
• Frequency in E influences R, R influences A’s contribution to fitness
The analysis confirms that niche construction can be a potent
evolutionary agent by generating selection that leads to the fixation of
otherwise deleterious alleles, supporting stable polymorphisms where none
are expected, eliminating what would otherwise be stable polymorphisms,
and generating unusual evolutionary dynamics. Even small amounts of
niche construction, or niche construction that only weakly affects
resource dynamics, can significantly alter both ecological and
evolutionary patterns. (Laland et al. 1999, p. 10242).

10. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
• Laland KN, Odling-Smee FJ, Feldman MW (1996). On the
evolutionary consequences of niche construction. Journal of
Evolutionary Biology 9: 293-316.
• Laland KN, Odling-Smee FJ, Feldman MW (1999). The
evolutionary consequences of niche construction and its implications
for ecology. Proceedings of the National Academy of Sciences USA
96:10242- 47.
• NC models are modification of multiplicative model (two loci)
• Locus E (alleles E, e), Locus A (alleles A, a), Resources R
• Frequency in E influences R, R influences A’s contribution to fitness
The analysis confirms that niche construction can be a potent
evolutionary agent by generating selection that leads to the fixation of
otherwise deleterious alleles, supporting stable polymorphisms where none
are expected, eliminating what would otherwise be stable polymorphisms,
and generating unusual evolutionary dynamics. Even small amounts of
niche construction, or niche construction that only weakly affects
resource dynamics, can significantly alter both ecological and
evolutionary patterns. (Laland et al. 1999, p. 10242).

11. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
Phenotypic Plasticity
• The term phenotypic plasticity describes the property of a
genotype to generate phenotypic variation in response to a
given range of environmental conditions.
• Various measures of plasticity exist and can be united within
the framework of a polynomial function: the norm of
reaction.
• NC models do not allow factors other than genotypes to
participate in the production of phenotypes.
• Niche construction advocates always consider the classic idea
of an influence on the population’s gene pool (frequency of
alleles that correspond to determinate phenotypic traits or
behaviours).

12. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
Phenotypic Plasticity
• The term phenotypic plasticity describes the property of a
genotype to generate phenotypic variation in response to a
given range of environmental conditions.
• Various measures of plasticity exist and can be united within
the framework of a polynomial function: the norm of
reaction.
• NC models do not allow factors other than genotypes to
participate in the production of phenotypes.
• Niche construction advocates always consider the classic idea
of an influence on the population’s gene pool (frequency of
alleles that correspond to determinate phenotypic traits or
behaviours).

13. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
Phenotypic Plasticity
• The term phenotypic plasticity describes the property of a
genotype to generate phenotypic variation in response to a
given range of environmental conditions.
• Various measures of plasticity exist and can be united within
the framework of a polynomial function: the norm of
reaction.
• NC models do not allow factors other than genotypes to
participate in the production of phenotypes.
• Niche construction advocates always consider the classic idea
of an influence on the population’s gene pool (frequency of
alleles that correspond to determinate phenotypic traits or
behaviours).

14. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
NC vc NCRN
• Reaction Norm (G)≡ The rule imposed by the genotype,
that determines the phenotype expressed in the population as
a function of the environment and other factors, can be
intended in different ways: it can go from simple mechanical
reaction rules up to complex algorithms considering aspects of
the environment, or from population either seen in the present
or preceding generation.
• Differences: Phenotypic outcome affects the environment.
Current phenotype undergoes selection, which affects on
population size. Future phenotypic outcomes depend on the
environment by reaction norm, which takes into account at
least the resource available in the environment and population
size.
• Common Feature: Aggregate Effect. NC models are
constitutively concerned with selection pressures, and while
selection pressures act on individuals, sorting them through
generations, they make sense only at population level.

15. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
NC vc NCRN
• Reaction Norm (G)≡ The rule imposed by the genotype,
that determines the phenotype expressed in the population as
a function of the environment and other factors, can be
intended in different ways: it can go from simple mechanical
reaction rules up to complex algorithms considering aspects of
the environment, or from population either seen in the present
or preceding generation.
• Differences: Phenotypic outcome affects the environment.
Current phenotype undergoes selection, which affects on
population size. Future phenotypic outcomes depend on the
environment by reaction norm, which takes into account at
least the resource available in the environment and population
size.
• Common Feature: Aggregate Effect. NC models are
constitutively concerned with selection pressures, and while
selection pressures act on individuals, sorting them through
generations, they make sense only at population level.

16. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
NC vc NCRN
• Reaction Norm (G)≡ The rule imposed by the genotype,
that determines the phenotype expressed in the population as
a function of the environment and other factors, can be
intended in different ways: it can go from simple mechanical
reaction rules up to complex algorithms considering aspects of
the environment, or from population either seen in the present
or preceding generation.
• Differences: Phenotypic outcome affects the environment.
Current phenotype undergoes selection, which affects on
population size. Future phenotypic outcomes depend on the
environment by reaction norm, which takes into account at
least the resource available in the environment and population
size.
• Common Feature: Aggregate Effect. NC models are
constitutively concerned with selection pressures, and while
selection pressures act on individuals, sorting them through
generations, they make sense only at population level.

17. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
Basic and Population NCRN Models
• The work with a basic NCRN model would be focused on the
exploration of the dynamics resulting from different kinds of
reaction norms with no variation of G across the population.
• Although basic NCRN studies seem insensitive to the
particular explanation for the ubiquity of G, such studies
might yield some results about the kinds of evolutionary
norms that exhibit evolutionary stability. NCRN studies can
be thought as preparatory to population models with multiple
reaction norms (e.g. G1 and G2).

18. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization

19. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization

20. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
NCRN, cultural evolution, and economical modeling
• Reaction norm and Rational Choice are both Rules that
share the picking of an element from a set of possibilities
according to external constraints.
• This picked up element is respectively the phenotype and the
chosen action.
• NCRN models introduce NC in a way that closes a gap
between biological and economic modeling.
vs
• NC models traits are cultural and genetic, and both kinds are
modeled by means of loci and alleles, where alleles correspond
to phenotypic alternatives that are fixed and there is no room
for plasticity.

21. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
NCRN, cultural evolution, and economical modeling
• Reaction norm and Rational Choice are both Rules that
share the picking of an element from a set of possibilities
according to external constraints.
• This picked up element is respectively the phenotype and the
chosen action.
• NCRN models introduce NC in a way that closes a gap
between biological and economic modeling.
vs
• NC models traits are cultural and genetic, and both kinds are
modeled by means of loci and alleles, where alleles correspond
to phenotypic alternatives that are fixed and there is no room
for plasticity.

22. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
NCRN, cultural evolution, and economical modeling
• Reaction norm and Rational Choice are both Rules that
share the picking of an element from a set of possibilities
according to external constraints.
• This picked up element is respectively the phenotype and the
chosen action.
• NCRN models introduce NC in a way that closes a gap
between biological and economic modeling.
vs
• NC models traits are cultural and genetic, and both kinds are
modeled by means of loci and alleles, where alleles correspond
to phenotypic alternatives that are fixed and there is no room
for plasticity.

23. Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization
First Formalization
• Resources Rt ,
• Population mass mt ,
• Genotype G , (reaction norm)
• Phenotype At ,
At : (Rt , mt , G ) → [0, Rt ]
Bt : (mt , At ) → +
Ct : (Rt , At ) → +
(1)
Ft : (Bt − Ct ) → +
Rt : (Rt−1 , At−1 ) → +
mt : (mt−1 , Ft−1 ) → +