Complexity in evolutionary theory helps think about human evolution
http://www.nhm.ac.uk/visit-us/whats-on/darwin/
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Presentation Notes
Be sure acknowledge power of focus on selection and extant Neo Darwinian theory, but to emphasize there is more to evolution than that….also that I find the traditional EEA concept too limiting, evolution is ongoing and that the contexts and patterns of evolutionary processes are what should interest us most (argue briefly against static take on selection and evolution more broadly)
Emerging Perspectives
• P h e n o t y p i c p l a s t i c i t y
• Developmental systems theory
• N i c h e C o n s t r u c t i o n
• Multi - inheritance perspective
• Biocultural approaches
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Presentation Notes
We are in the midst of significant enhancements in complexity and diversity in evolutionary theory, with the role for behavioral modification of social and ecological spaces, and their inheritance, becoming a key factor. Our grasp of patterns and contexts of selection and the ways in which social, epigenetic and developmental interactors affect outcomes is growing by leaps and bounds. We also are increasingly realizing that social and experiential contexts shape bodies and behavior, affecting trajectories in more substantial manners than previously envisioned. In this talk I will review current proposals for integrating perspectives from niche construction and multi-inheritance into investigations, models, and explanations for the evolution of human, and more broadly primate, behavior.
Plasticity as normative
• Developmental plasticity
• Phenotypic plasticity: “the production of multiple phenotypes from a single genotype, depending on environmental conditions”
• Expression of phenotypic plasticity via changes in behavior, physiology, morphology, growth, life history, and demography
• Plasticity can occur in both individually and inter-generational contexts
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Mary Jane West-Eberhard’s broad overview (2003) of developmental plasticity and evolution led her to suggest that plasticity is one of the key factors for our understanding of adaptive evolution. She argues, like many other prominent evolutionary biologists, that reducing the processes of development and evolutionary change to genomic levels is not always possible or preferable. These analyses demonstrate that evolved plasticity in development enables the evolution of new or variant, but adaptive, phenotypes without substantial, or even marked, genetic change. This phenotypic plasticity and its relation to ecologies and evolutionary patterns is of core interest in evolutionary theory. Recent reviews define basic phenotypic plasticity as “the production of multiple phenotypes from a single genotype, depending on environmental conditions” (Miner et al. 2005). However, more important than the basic definition is the evidence that a range of organisms express phenotypic plasticity via changes in behavior, physiology, morphology, growth, life history, and demography and that this plasticity can occur in both individually and inter-generational contexts (Miner et al. 2005, Pigliucci 2001). Research into modeling this plasticity, its potential adaptive value and contexts, and its ecological impact all suggest that phenotypic plasticity is a significant factor for many organisms’ evolutionary histories and current behavior/morphology.
– some hereditary variations are nonrandom in origin
– some acquired information is inherited
– evolutionary change can result from instruction as well as selection
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Presentation Notes
The biologists Eva Jablonka and Marion Lamb (2005) call for a renovation in evolutionary theory at the start of the 21st century, a “new” new synthesis in how we model evolution. They argue for recognition of “evolution in four dimensions” rather than a focus on just one. Their main point being that practitioners of traditional Neo-Darwinian approaches focus on one system of inheritance: the genetic system of inheritance. Jablonka and Lamb argue for adding a perspective wherein three other inheritance systems also, potentially, have causal roles in evolutionary change. These other systems are the epigenetic, behavioral, and symbolic inheritance systems. Epigenetic1 inheritance is found in all organisms, behavioral inheritance in most, and symbolic inheritance is found only in humans2. “Information is transferred from one generation to the next by many interacting inheritance systems…Variation is also constructed, in the sense that, whatever their origin, which variants are inherited and what final form they assume depend on various “filtering” and “editing” processes that occur before and during transmission.This moves past standard Neo-Darwinian approaches. Many organisms transmit information via behavior, thus acquisition of evolutionarily relevant behavioral patterns can occur through socially mediated learning. This transmission of information occurs without having any linkage to genetic systems that natural selection (in a Neo-Darwinian view) can target. Symbolic inheritance comes with language and the ability to engage in information transfer that can be temporally and spatially complex, contain a high density of information, and convey more than material descriptions. This allows for the acquisition and reproduction of a variety of behaviors, perceptions, beliefs, potentially beneficial for human populations that have no genetic basis or linkage. Models using this system will be by necessity become more complex than the generally linear genetic models of Neo-Darwinian behavioral theory (such as kin selection, the favoring of close relatives due to their high degree of shared genotype, for example). However, such models may be better attuned to the actual interactions of systems. Specifically in terms of anthropology this perspective forces an evolutionary concern with the way in which bodies and behavioral and symbolic systems construct and interact with social and ecological niches and how, in turn, these systems interact with epigenetic and genetic systems. This perspective blurs any clear prioritization in inheritance systems and forces a move away from approaches that are limited to either social or biological foci.
Niche construction– Niche construction is the building and
destroying of niches by organisms and the synergistic interactions between organisms and environments
– impacts/alters energy flows in ecosystems through ecosystem engineering
– demonstrates that organisms modify their, and other, organisms’ selective environments
– creates an ecological inheritance
– in addition to natural selection contributes to changes over time
Presenter
Presentation Notes
Building on work of Richard Lewontin (1983) and earlier perspectives proposed by Ernst Mayr (1963) and Conrad Waddington (1959), and even taking from the “extended phenotype” concept of Richard Dawkins (1982), F. Odling-Smee, Laland, and Feldman (2003) formalized and proposed Niche Construction as a significant evolutionary force. Niche construction is the building and destroying of niches by organisms and the synergistic interactions between organisms and environments. Niche construction creates feedback within the evolutionary dynamic, such that organisms engaged in niche construction significantly modify the evolutionary pressures acting on them, on their descendants, and on unrelated populations sharing the same space. Niche construction impacts/alters energy flows in ecosystems through ecosystem engineering creating an ecological inheritance and, like natural selection, contributes to changes over time in the dynamic relationship between organisms and environments (niches). Niche construction reflects synthetic unities of ecological, biological, and social niches rather than treating them as discreet spheres (Flack et al. 2006, Fuentes 2009, Odling-Smee et al. 2003) Olding-Smee et al (2003) explicitly state that ecological inheritance, via material culture, and niche construction in general can occur via cultural means. They state that humans are the “ultimate niche constructors” and that adding niche construction to attempts to understand human systems makes such attempts more complicated (bypassing more simplistic Neo-Darwinian adaptationist accounts). They see cultural processes as providing a particularly robust vehicle for niche construction. Odling-Smee et al. (2003) propose a specific model for human genetic and cultural evolution that they call a Tri-inheritance vision model (TIV). Under TIV human behavior results from information acquiring processes at three levels: population genetic processes, ontogenetic processes and cultural processes. Niche construction in humans emerges from all three of these processes each of which can impact patterns, contexts, and structure of natural selection. They state “Much of human niche construction is guided by socially learned knowledge and cultural inheritance, but the transmission of this knowledge it itself dependent on preexisting information acquired through genetic evolution, complex ontogenetic processes, or prior social learning” (Odling-Smee et al. 2003:260-261).
niche construction: why should we care?
• niche construction as a core evolutionary process and the role of social and ecological inheritance as it relates to intergenerational interactions and relationships
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Presentation Notes
Core role of ecological and social inheritances
Human evolution…• Human behavioral evolution must be seen as a system
evolving, not single traits
• Niche construction is a core factor in human behavioral evolution
• Ecological and Social inheritance are core to human behavioral action and change.
• Enhanced communication and symbol are central
• Feedback rather than linear models are central
• Must consider the potential impacts of diverse biological and social/cultural processes in behavioral and evolutionary change
• Must include a specific role for flexibility and plasticity in behavior and development as a baseline
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Presentation Notes
The ability of humans to modify their surroundings is central to any explanation of human behavior. These surroundings include the social, the biotic, and the abiotic. Understanding human evolution requires assessing the interactive and mutually mutable relationship humans have with their social and structural ecologies. We must accept the possibility that selection pressures can be modified as they are occurring and that human response to selective challenges need not always fit the standard ecological parameters of the selective force. That is, human toolkits (somatic and extra somatic) might result in innovation that adds elements into a system that standard ecological and selection modeling (such as behavioral ecology or ND Sociobiology) cannot foresee or does not normally include. For example, behavioral innovation in the use of controlled fire as a response to pressures exerted by climate stress, predation risk and the extraction of nutrition from complex food sources. Humans almost always exist in a place where there have been humans before them. Social and ecological parameters are impacted by the previous generations and individuals in subsequent human generations inherit a much larger amount of information than do any other organisms (at least since the advent of rudimentary language and tool use). Even when moving into new territories humans carry some portion of the knowledge of past members of their group with them (social and material). This provides humans with a broader ability (more ways) to respond to challenges though a more diverse array of means than other organisms. It also might mean that humans can respond at quicker rates than most complex organisms when faced with strong selective challenges. It also means that humans may come upon multiple effective responses to the same challenges and potentially share them across individuals and possibly even groups. Humans use their extensive ability to convey information to respond to the basic ecological challenges that they face, thus models should include a role for a type of communication not possible in other organisms1. This is probably true for most evolutionary models in complex multicellular organisms; however it should be explicit in hypotheses and models for humans (as it already is in many). Feedback in a system implies that rather than moving from A to B the system may modify itself during the processes of acting. If feedback is a component of a system outcomes are not necessarily based on the initial behavioral pattern within the system. Human responses to predation pressures or foraging challenges might be good examples, with constant modification of human behavior based on the experiences and patterns of the humans and of the predators/prey or forage targets. Most hypotheses for the evolution of human behavior rely strictly on natural selection as the only significant evolutionary force in the structuring of human behavior. However, we should also include possible impacts from gene flow and drift in genetic, phenotypic and behavioral responses. Dual inheritance theory (DIT) focuses on the possibility that selection acts on human cultural behavior, here I extend that and suggest that patterns of flow and drift can impact behavior as well as genotypic factors. Selection need not always be invoked to explain the innovation and spread of behavior. When it is invoked we should also be prepared to include models that accept selection as acting on levels beyond a selfish gene or selfish individual focus (as highlighted by Sober and Wilson 1998, Odling-Smee et al. 2003, Oyama 2000, Oyama et al. 2001) It is most likely that the majority of human responses that result in behavioral change over time are not optimal, even if they do result in adaptation. It is likely that the majority of successful human responses reflect a pattern of plasticity and flexibility resulting from a cohort of selection pressures as opposed to specific selection for a particular adaptation in response to a single selective pressure. This suggests that explanations that focus on the link of a particular behavior to a specific adaptive outcome may be poor models for human behavioral evolutionary processes.
We need to find some way to explain why Homo took off and the rest went
extinct
From Kingston 2007
Taking a more careful look at intragroup behavior …
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Mainstream approaches sin the inquiry into human evolution frequently look for “big moments,” monumental shifts in selection events/responses that catapult a lineage from one stage t the next …. Is it possible that in the mainstream approaches to examining human evolution we have overlooked some core aspects that might be right under our noses…aspects critical to niche construction, behavioral and even symbolic inheritance?
More specifically…
versus
How do we think about social organization and social groups In human ancestors?
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More specifically, have we ignored some important possibilities and within and between group behavior that might provide not only additional information about human evolutionary trends, but new explanatory models and even insight into modern human behavior.
The “euro-pair” is not the basal unit of human social organization…we need to
envision social group, and all of its members, as nexus of human evolution
Art by Tom Rhodes
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Presentation Notes
We have to move away form these notions that the basal unit of analyses for human behavior is the pair or the male-female unit or even the mother infant unit….we do not live in dyads nor have dyads been the main unit of interaction for humans for millions of years. Expanding outside this pair focus might enable us to get a better grasp on why we do what we do, form an evolutionary sense.
intergenerational relationships in the context of human evolution
• (Gettler) male carrying• (McKenna, Ball, Trevathan)
sleep, childcare, and child development
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Presentation Notes
Over the last decade or so a number of researchers have re-introduced a focus on intergenerational interactions (more than just mother-infant interactions) as core focal points for evolutionary questions/investigations Discuss each of the following: (Hrdy) cooperative breeding (Lamb, Gray) male care and complex parenting (Gettler) male carrying (McKenna, Ball, Trevathan) sleep, childcare, and child development
cooperation in human evolution
• (Gintis & Fehr) cooperation as norm
• (Fuentes et al.) cooperation and nicheconstruction
• (Sussman and Hart) predation and cooperation
• (Oka and Fuentes, Horan et al.) Trade routes and “out cooperating” Neanderthals
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Presentation Notes
All of the previous examples resonate well with the increased attentions recently to the myriad of ways in which extensive and substantial cooperation has been positioned as central to human evolution. Review these proposals: (Gintis & Fehr) cooperation as norm (Fuentes et al.) cooperation and niche construction (Sussman and Hart) predation and cooperation (Oka and Fuentes, Horan et al.) Trade routes and out competing Neanderthals
Niche Construction• An increasing brain size and an extended period of,
and effort in, child care in the genus Homo during the Pleistocene lead to: – more cooperative interactions between group members,
across generations – an associated increase in communicative complexity, – increased effectiveness at avoiding predation, – and an expansion of the types and patterns of habitat
exploited.
Presenter
Presentation Notes
Let’s outline specifically what type of niche construction might be happening in populations of the genus Homo in the Pleistocene… An increasing brain size and an extended period of, and effort in, child care in the genus Homo ~1.5 mya lead to: more cooperative interactions between group members, across generations an associated increase in communicative complexity, increased effectiveness at avoiding predation, and an expansion of the types and patterns of habitat exploited.
Niche Construction• As Homo became more costly,
predators shifted emphasis to easier prey, reducing the overall selective pressure of predation (Fuentes et al. 2010).
• Homo experienced increased opportunity for social interactions, range exploration, and testing a variety of novel foraging opportunities, all of which demanded—and fed back into—an emerging higher cognitive functioning.
Niche Construction
• Heritable components of human niche construction:– tool use– fire use?– increased infant survivorship – increased information
transference via more-complex communication patterns
…all tied to an evolving hominin cognition, which facilitated success in a diverse array of environments.
connecting the dots
• A model of integrated cooperation as a component of the human niche- one of the reasons homo is successful
– the role of children and child “care”: costs and payoffs
– Social niche of alloparenting
– Ecological and social inheritance
– Multi-generational Cooperation
Social mind:Social relationships
Are importantKin selection and
Reciprocal altruismAs salient forces
Primate mindComplex
social networksIncreased reciprocity
Social mammals
Gregariousmonkeys
ApesIncreased reliance on
Social networksand cooperative
Alliances andIncreased reciprocity
Cultural mind
Humans
Niche constructionVia social complexity
and increased cooperation
Niche construction via increased social complexity,
property of extensive social niche construction and complex cooperation
with reciprocity as core behavioral pattern
Males and immatures participate
extensively in allocare
Immatures contribute to foraging and anti-predator
behavior Extended allocare
Primate mindComplex
social networksIncreased reciprocity
Immatures contribute to social niche
Immatures participate in
group symbolic communication
Extended development
Any evidence for this?
• Fossils
• Humans and primate behavior
• Mirror neurons and endocrine physiology as mechanisms?
Children are integral as part of the human evolution
This means we need to think about past and present intergenerational relationships as part of the human evolutionary trajectory and consider them when modeling what it
means to be human
Thanks to
• Darcia Narvaez
• Participants in this symposium
• College of Arts and Letters, University of Notre Dame
