Full
reference:
Gabora,
L. (2006). The fate of evolutionary archaeology: Survival or extinction? World
Archaeology, 38(4), 690-696.
The
Fate of Evolutionary Archaeology: Survival or Extinction?
Liane
Gabora
Address for correspondence:
L. Gabora
Psychology
University of British Columbia
Okanagan campus, 3333 University Way
Kelowna BC, V1V 1V7, CANADA
Phone: (250) 807-9849
Fax: (250) 470-6001
Abstract
It is important to
be clear as to whether a theory such as evolutionary archaeology pertains to
biological evolution, in which acquired change is obliterated at the end of
each generation, or cultural change, in which acquired change is retained. In
evolutionary archaeology, (1) the population is said to consist of artifacts,
yet (2) artifacts are said to be phenotypic. Neither (1) nor (2) is necessarily
problematic in and of itself, but the two are inconsistent, as the first
pertains to cultural change whereas the second to the biological evolution of
humans. A first step to avoiding this problem is to recognize that there is a
need for a theory of change specific to human culture. Referring to ongoing
work using a related approach to cultural change, it is suggested that the
inconsistencies in evolutionary archaeology, though problematic, are not
insurmountable.
Key Words
acquired
characteristics, evolutionary archaeology, inheritance, lineage, natural
selection, phenotypic trait, unit of replication
Artifacts undeniably exhibit identifiable patterns of change over time,
or Ôdescent withÕ modification, as do biological organisms. The goal behind an
evolutionary approach to archaeology seems reasonable and straightforward: to
develop an overarching framework for analyzing how artifacts are related to one
another, borrowing concepts developed for this purpose in biology such as
lineage, heritability, and drift (changes in the
relative frequencies of different alleles—forms of a gene—as a
statistical byproduct of randomly sampling from a finite population).
This kind of framework would be indeed be of value, and those who have striven
to go beyond their primary area of expertise to build such a framework are to
be commended, for it is easy to underestimate the difficulty of such an
endeavor. However, much of this
literature is riddled with serious conceptual errors. Some have been debated at
length (e.g. Bamforth
2002; Boone and Smith 1998; Kehoe 2000; Loney 2000; Lyman and OÕBrien 1997;
Murray 2002; Neff 2000; OÕBrien 1996a, b, 2005; OÕBrien and Lyman 2004; Preucel
1999; Schiffer 1996; Shennan 2002; Spencer 1997; Wylie 2000). Others, however,
have not been addressed, or require elaboration. The goal of this paper is to
tackle these errors because, as I see it, they are exactly what stands in the
way to a genuine theory of how artifacts evolve.
If Artifacts are the Phenotype
then Humans are the Population
Let us jump right in by addressing a glaring problem that comes to
light when evolutionary archaeologists are charged with not having a clear
answer as to what the unit of replication is in the evolution of artifacts.
Lyman and OÕBrien answer that Darwin did not know what the unit of replication
was when he came up with the theory of how organisms evolve through natural
selection, so they neednÕt be concerned that they donÕt yet know what the unit
of replication is with respect to the evolution of artifacts (1998:619).
However, Darwin did know
what the unit of replication is: the organism. It is the unit of heredity--the gene--that he did not know.
This
lack of clarity as to what is the unit of replication leads quite naturally to
a persistent error as to what is the population. OÕBrien claims Òin
archaeology, not surprisingly, the population consists of artifactsÓ (2005:30).
But this is surprising,
for earlier in the same paper he wrote:
The only defense that Brew could see for
even thinking of using an artifact-classification system Ôbased upon
phylogenetic theory is that the individual objects were made and used by manÕ
(1946:55)--a point that, to Brew at least, was so obvious as to
be trivial. As we shall see, however, that point is the keystone to applying
Darwinism to the archaeological record. (2005:28)
This leads one to believe that OÕBrienÕs position is that it is because
humans evolve through natural selection that Darwinian theory is relevant to
artifacts. But in the evolution of humans through natural selection, the
relevant population consists of humans, not artifacts. Indeed this interpretation of his
position is strengthened a few lines after the statement that the population is
artifacts, where he writes:
Evolutionary archaeology rests on the
premise that objects in the archaeological record, because they were parts of
past phenotypes, were shaped by the same evolutionary processes as were the
somatic (bodily) features of their makers and users. (2005:30)
Here it is unmistakable that OÕBrien is speaking of biological
evolution operating on populations of humans rather than cultural evolution
operating on populations of artifacts. Elsewhere this inconsistency appears even
within a single sentence, for instance
ÒIn evolutionary archaeology, the population is artifacts, which are
viewed as phenotypic featuresÉÓ (Lyman and OÕBrien, 1997: p. 616). To be
consistent with the first part of the sentence, Ôthe population is artifactsÕ,
each artifact must be understood to possess a unique genotype, or something
that plays the role of a genotype, which gets expressed phenotypically. However
the second part claims that artifacts are Ôviewed as phenotypic featuresÕ. How
can something be both (1) an entity with a phenotypically expressed genotype,
and (2) a mere phenotypic feature? One gets the impression that in the second
part of the sentence Lyman and OÕBrien mean that artifacts are phenotypic
features of the human genotype. But then once again the relevant population is
the set of interbreeding humans, not artifacts. It is important to see here
that the problem is not
that they consider artifacts part of the human phenotype. That is not at issue.
The issue is that the framework they are constructing is internally inconsistent.
Why it Matters that Artifacts Inherit Acquired
Characteristics
The confusion regarding the unit of replication and the population are
all the more problematic because the mechanisms underlying the biological
evolution of humans and the cultural evolution of artifacts are different, as
evidenced by the fact that while biological organisms are protected from change
accrued during a lifetime (for example if one cuts off the tail of a rat, its
offspring still have tails of normal length) for artifacts this is not the
case. Once someone made a cup with a handle, cups with handles were here to
stay. Indeed in human culture, inheritance of acquired characteristics is not
just the exception but the rule (though note that here ÔinheritedÕ merely means
transmitted or Ôpassed onÕ without implying genetic mediation). Characteristics
of artifacts actually change faster than the genomes of the individuals who
produce them. The mathematical theory of natural selection developed to
describe biological evolution[1]
is only applicable when there is no inheritance of acquired characteristics (or
at least it must be negligible compared to change due to differential
replication of individuals with heritable variation competing for scarce
resources), a condition clearly not met in the evolution of culture.
Since biology and culture are different (though
intertwined) processes with different underlying mechanisms, it is important to
be clear which of them one is theorizing about: the one where inheritance of
acquired characteristics is prohibited (biology), or the one where it is not
(culture). The EA literature is rampant with passages that reveal a lack of
appreciation of this key point. Recall BrewÕs objection to applying Darwinism to
artifacts merely because they are made by humans. What Brew understood (either
rationally or intuitively), and what OÕBrien missed, is that since artifacts
can change much more rapidly than the genomes of the individuals who make them,
change in artifacts cannot be explained by recourse to the fact that humans are
evolving through natural selection. It is important to emphasize that no one
disputes that humans evolve through natural selection; on this point, OÕBrienÕs
characterization of his critics is distorted. No one ever argued for instance
that Òintelligence and motivation exempt humans from the evolutionary processÓ
(2005:30-31) or that Òthey are not subject to natural selection and driftÓ
(2005:31) or that Òadaptive plasticity shields humans from evolutionary
processesÓ (2005:31) or that Òhumans can dodge natural selection by making
choicesÓ (2005:31). That would indeed be ridiculous. The argument is subtler,
and can perhaps be understood through the following analogy. One can use
knowledge about the wind to make predictions about the speed and position of an
unmanned boat adrift at sea. But if the boat is manned and equipped with oars
or a motor, wind may not be the major causal factor determining its speed and
position. It is not that the boat is no longer affected by wind; it is that
some other causal factor is playing an influential role.
Special Laws for Humans?
EAÕs refusal to accept this appears to stem from the unfounded
presumption that it is incompatible with human behavior as being phenotypic. As
OÕBrien and Lyman (2004) put it:
That artifacts are phenotypic is
nonproblematic to most biologists, who routinely view such things as a birdÕs
next, a beaverÕs dam, or a chimpanzeeÕs twig tools as phenotypic traitsÉ If the
behaviors are phenotypic then the results of the behaviors are phenotypic as
well. But many of us have a problem with viewing human behavior as phenotypic.
We see ourselves as being quantitatively and/or qualitatively so different from the rest
of the natural world that we warrant not only a whole new set of laws but also
a different set of philosophical questions with which to examine ourselves. EA
does not accept that argument. (p. 179)
Their use of the word ÔlawsÕ is misleading, as if a phenomenon has to
attain the status of the Ôlaw of gravityÕ to be worthy of attention. It is
ironic though, in a sense, that they chose this word, because the subject of
law does address an
immense body of questions and issues pertaining solely to humans. The law does
not prescribe rules of conduct for rats or rocks. And of course, law is not
unique in this respect. At least as many disciplines deal exclusively with
human affairs (political science, literature, sociologyÉ) as with affairs not
restricted to the human realm (physics, chemistry, geologyÉ).
OÕBrien and Lyman repeatedly claim that their approach
is more scientific than alternatives, stressing ÒHypotheses derived from
theories must have testable implications (2004, p. 187).Ó In arguing that
natural selection at the biological level provides all the explanatory power we
need, we are led to the hypothesis that we make artifacts like popcorn makers
and Powerpuff dolls because we are genetically predisposed to, and if this is
born out I will have newfound admiration for this approach. However I suspect
that, much as physics does not get us far toward an explanation of, say,
predator-prey relationships, biology will not go far toward an explanation of
the design of cultural artifacts.
The indisputable fact is that we are different from the rest of the natural world, both
qualitatively and quantitatively. Nothing is gained by letting
ideals (concerning the equality of all forms of life) obscure the evidence
before our eyes that we (for better or worse) have abilities other species
lack. Considerable effort has
gone into attempting to explain human functioning and behavior in terms of
theories that have proven successful for explaining the natural world. And
these efforts have been successful to the extent that humans share
characteristics with other aspects of the natural world; for example in
understanding how the eye works or how disease spreads or even aspects of
courtship behavior. But these efforts have not taken us very far when it comes
to explaining characteristics by which we differ from other elements of the natural
world. And what makes us most unique is exactly that aspect of human nature
that is of relevance to archaeology: our propensity to not just generate
novelty but to build on it cumulatively, adapting old ideas to new circumstances
(the Ratchet effect). The upshot, as Renfrew (1982) pointed out
some time ago, is that genetically inherited traits likely play but a minor
role in the form of a human-made artifact.
This does not imply that artifacts do not affect biological
fitness, or that biological constraints do not affect their design. It just
means that even if you had a complete understanding of biology, and in
particular of genes and how they are expressed in different environments, you
would not have enough information to predict or even interpret change in the
archaeological record. Moreover, archaeological data may still give evidence of
phenomena observed in biology such as lineages and drift. But when such
phenomena are observed they need not be attributed to natural selection. Indeed drift and
other population phenomena have been observed in a computer model of cultural
evolution in which neural network based agents (without anything playing the
role of genomes) evolve gestures through a re-iterated non-Darwinian process of
invention and imitation, no natural selection at all (Gabora 1995).
Conclusions
This paper is far from the first to point out flaws with EA. Attacks
have come from multiple directions, and addressed multiple aspects of its
claims. But that does not mean that EA is doomed to extinction. Perhaps
evolutionary theory does have a role to play in a workable theory of artifact
change, and the goal of constructing and analyzing artifact lineages using
concepts from biology need not be forsaken, but it is time for proponents of EA
to cut their losses and rethink their strategy.
A first step is to resolve conceptual inconsistencies
(outlined above) concerning the unit of replication, the population, the
inheritance of acquired characteristics, and so forth. A next step is to forgo
that biological evolution can provide a complete explanation for artifact
change. Moreover, it may be that the cultural process overlying it is quite
different from how it is now conceived. In the scheme I put forth, the unit of
replication in culture is the integrated web of memories, concepts, ideas, and
attitudes that constitute an internal model of the world and how to conduct
oneself in it: a worldview (Gabora 1998, 1999, 2000, 2004; Gabora and Aerts
2005a). Like the autocatalytic sets widely thought to be the earliest forms of
life (Gabora 2006; Kauffman 1993), worldviews replicate through an emergent,
autopoietic process, without a self-assembly code (like the genetic code), and
thus acquired characteristics are inherited. Novelty is introduced not randomly
but through strategic, creative processes (Gabora 2005). Artifacts mediate the
process by which onesÕ worldview is transmitted, in a clumsy, piecemeal manner,
to others. One cannot examine the state of a worldview, but much like
footprints in the snow tell us much about the animal that left them, artifacts
tell us much about the minds that created them.
So is the fate of EA survival or extinction? The
question itself assumes there are only these two possibilities, which is
consistent with the Darwinian perspective espoused by evolutionary
archaeologists, in which only the fittest survive. However, in the alternative
proposed above, where culture evolves through a process more akin to the
evolution of pre-DNA life than post-DNA life¾a process that in fact violates the assumptions that make natural
selection applicable to its description (Gabora 2006; Gabora and Aerts 2005b)¾survival
and extinction are not the only two possible fates. Because uncoded replicators
inherit acquired traits, they may either survive intact or go extinct, or do
something in between these two extremes: transform. EA may have to do considerable
transforming to stay afloat. But if the missing ÔtraitsÕ are ÔacquiredÕ,
vestiges of the enterprise as currently practiced and advocated may linger in
theories that float above it.
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