The ecology of longevity: the relevance of evolutionary theory for digital preservation

Software and data can be considered as digital
organisms that function in a "digital ecosystem"
of computers. The concept of ecology has been
borrowed from biology by other disciplines
for explaining or describing a variety of
phenomena. In some cases ecology and other
concepts from evolutionary theory are only used
as metaphors; in other cases attempts have been
made to apply an adapted version of the theory
to the evolution of non-biological phenomena.
We think it makes sense to borrow the
notions from evolutionary theory in thinking
about digital longevity. In this paper we will
explore the potential of Darwin's theory as an
explanatory framework for digital survival.
The construction of a theoretical foundation
serves to answer questions of why some criteria
or characteristics will guarantee the "survival"
of digital objects better than other ones.
Taking an evolutionary view will also make
clear that there is no such thing as digital
permanence for eternity: some objects only have
better
chances
to survive than other ones. In
computing technology, there is a struggle of
survival of the fittest going on. In this struggle,
new technologies arise as modifications or
adaptations of earlier technologies and the
older ones die out when newer technologies
are stronger or better suited for their tasks.
The digital objects that are already in existence
have to be adapted to the new technological
surroundings, otherwise they become extinct.
Spencer originally coined the phrase "survival of
the fittest" in 1864, drawing parallels between
his ideas of economics and Darwin's theory of
evolution, which is driven by "natural selection".
With respect to digital objects, it is people who
are actively or passively involved in making the
selections, thus deciding which digital objects
survive and which do not.
As electronic digital data can only be understood
using computers and software to "translate"
them into visible or audible form, the media
and data formats that are specific for hard-
and software change according to the same
evolutionary principles. If we accept this
view, we can start to ask ourselves: which
characteristics (comparable to the "genetic
properties" of living organisms) may influence
the chances of digital survival of data? This is
however not unproblematic, as it is typically
with hindsight that we see which (traits
in) a biological species have survived and
how the evolutionary process took place. The
explanatory power of evolution theory is a
posteriori, not a priori. It may therefore be
difficult to predict which traits are good for
survival.
We will explore the possible use of the
concept of evolvability, which is usually
defined as the ability of a population of
organisms to generate genetic diversity, hence
giving a measure of an organism's ability to
evolve. Maybe there is a parallel here with
respect to digital objects. For instance, if we
look at several formats for Microsoft Word
(.doc, .rtf, .html, .xml (2003), .ooxml) then we
see an increase in usability/interchangeability,
and hence probably: evolvability.
We can break down the survival problem to
questions concerning:
-
The physical attributes of the media (tape,
disk, etc.)
-
The media format (density, size, etc.)
-
The data content (integrity of the bits and
bytes)
-
The data format (the structure of the bits and
bytes)
-
The metadata content (the substantial
description of the data)

2
-
The metadata format (the format in which the
metadata is described)
-
The interlinking (the degree to which data is
linked both internally and externally); a web
of interlinked information is an ecosystem of
its own.
We will demonstrate how digital preservation
strategies such as technology preservation,
software emulation, and data migration fit in
an overarching evolutionary framework. The
ecological approach also shows that it makes no
sense to try to express the time horizon for the
preservation of digital objects as a specific or
indefinite period of time, but that we can better
think in terms of "chances of survival".
The evolutionary framework can be used to
argue why certain attributes and formats are
more likely to survive than others. Also,
analogous to natural selection, we will make
clear that there is no single "best" strategy
for survival of digital data. Some factors
simply increase the chances of digital longevity,
whereas other factors reduce these chances.
Good factors for longevity may be bad for other
desired characteristics. For example: stripping
executable information from data improves its
longevity, but hinders its functionality. It may
also be so that some factors are intensely
ambiguous for longevity. We may now think that
"wrapping" text in WordPerfect in the 1990s
was (with hindsight) not so good for survival,
and that packaging it in Microsoft Word seems
acceptable. This is probably related to the
status (or market dominance) of the software
packages. Similarly, packaging data in SGML
in 1990 might have been not so good, while
packaging it in XML in 2009 seems excellent. In
the end, the environment determines what was
good and what was bad for longevity.
So, when the whole "technological ecosystem"
changes, what was well adapted before the
change may appear to be ill suited in the
next technological phase. Digital preservation
strategies can use the principle of digital
selection in order to maximize the adaptation
of digital objects to their environment, thus
increasing their chances of digital longevity.
Whether it makes sense to apply evolution
theory to digital curation can be studied by
looking at a number of parallels in other
scientific domains. We will deal briefly with
attempts to use Darwin's ideas in the social
sciences and in technology. In the social sciences
the idea of a "social ecology" was already applied
and empirically tested in the 1920s by, among
others, Robert Park and Ernest Burgess of the
"Chicago School" of urban ecology. With respect
to man-created systems it is probably better
to use the ideas on evolution by Lamarck.
Lamarckism is the idea that an organism can
pass on characteristics that it acquired during
its lifetime to its offspring (also known as
heritability of acquired characteristics or soft
inheritance).
Several researchers have proposed that
Lamarckian evolution may be accurately applied
to cultural evolution. Human culture can
be looked upon as an ecological niche-like
phenomenon, where the effects of cultural
niche construction are transmissible from one
generation to the next. Ecological notions
on the evolution of software, in which ideas
and characteristics of programming languages
compete with each other, have been formulated
in information science. Inheritance is an
important concept with an evolutionary basis.
The development of open source software has
also been described as evolving in a Lamarckian
fashion. Ensuring free access and enabling
modification at each stage in the process means
that the evolution of software occurs in the fast
Lamarckian mode: each favourable acquired
characteristic of others' work can be directly
inherited.
Kauffman and Dennett point out the parallels
between biological evolution and technological
evolution. They distinguish two stages: (i)
explosion of the number of greatly different
designs when there are still many unoccupied
niches; (ii) microevolution where the existing
designs are optimised for competition in
existing niches.
It is also useful to compare the selection and
survival of digital information with that of
analogue information. In both cases there is
"information selection" and evolution. What
makes the digital world so different from the
analogue world?
Next we will treat a few examples of the
evolution of computing technologies, software,
file formats and data sets, which will illustrate
how well evolutionary theory is suited for