


































v2018i1


Volume 1, Issue 1

Letters and Notes

Implications of Two Opposing
Variations of Neutral Theory
Jonathan Bartlett
DOI: 10.33014/issn.2640-5652.1.1.bartlett.2

In evolutionary biology, neutral theory has been gaining
more and more ground since it was originally proposed by
Motoo Kimura in 1968 (Kimura, 1968). It was originally
proposed as a mathematical way of understanding the re-
lationship between allele variations and population sizes in
population genetics, but was later applied to molecular evo-
lution as well (Dietrich, 1994).

Popular theories sometimes shape the thinking about a sub-
ject far beyond what the technical aspects of the theory
suggest. This is true both for popular and professional au-
diences, as even for professionals, popular principles often-
times fill in the gaps in understandings (see Bartlett (2017)
for a discussion of this).

While selection has previously stood in the gap for these
types of understandings in biology, today neutral theory
has begun to takes its place. Interestingly, in the case of
neutral theory, the theory implied by the data is actually
significantly at odds with the larger interpretation and ap-
plication of it.

The question turns on whether neutral evolution is merely
a description of the peculiar features that are found in the
organisms present in the earth today, or if neutral evolution
is due to general features of evolution itself (i.e., they would
exist no matter how biology was configured). I will call the
first theory “observational neutral theory” and the second
one “comprehensive neutral theory.”

In observational neutral theory, neutral theory merely
points to observations about present mutations in present
organisms. It makes no claims about evolution in general,
evolution past, nor the requirements for neutral evolution
to take place. It merely points out that most mutations we
observe are nearly-neutral or of low effect (Eyre-Walker and
Keightley, 2007), and therefore selection has very little ef-
fect on which mutations survive in the population (Sanford
et al., 2007). Genetic drift therefore becomes the dominant
mode of observable evolution. Selection, when it acts, is

primarily purifying selection (Dietrich, 1994). This type
of neutral theory does not speculate on why this is the
case—more to the point, the reason for why neutral evo-
lution occurs is basically outside of its scope. That is, it
leaves out the specific molecular requirements that would
lend themselves to neutral evolution.

In comprehensive neutral theory, the dominance of neutral
evolution is not only in the observed present, but is also
the key to all of evolution. That is, evolution needs no
guidance from natural selection to do its work (though it
may have some). According to this view, neutral mutations
and genetic drift are all that is needed to get all of the
precise mechanisms available within biology.

The reason that this distinction is important is that I have
found that, in conversation, many biologists free-float be-
tween the two theories. Neutral theorists often start in
the observational theory, beginning by saying that evolu-
tion as we observe it obeys the principles of neutral theory.
Since neutral theory is dominant in the process of evolu-
tion today, many neutral theorists then generalize to the
comprehensive theory and say that because it is dominant
today that neutral theory must have been equally dom-
inant in the past. Therefore, neutral evolution must be
really powerful, because all of biology is the result of neu-
tral evolution. However, one can then point out that the
reason neutral evolution works in the present is because
mutational hot-spots are contained in less-sensitive areas
of the genome. When pressed, the neutral theorist quickly
switches from a comprehensive theory back to an observa-
tional theory, usually citing natural selection as the reason
for such a propitious distribution of hotspots. Recognizing
the distinction between the observational and comprehen-
sive theories of neutral evolution is important for critical
thinking about neutral theory. This is somewhat amusing
because one of the supposed benefits of neutral theory is
getting around problems of selectionism and adaptation-
ism in evolution. However, when pressed on shortcomings
in neutral theory, this is precisely where neutral theorists
often go.

Comprehensive neutral theory is unworkable, because the
machinery in cells and organisms are precise mechanisms.
Therefore, random wanderings in genome space will not
produce them in any amount of time. My own viewpoint



52 Letters and Notes

is that the observational neutral theory is a fairly accurate
representation of what we know about modern evolution,
but it needs to be underpinned by something other than
selectionism for a foundational theory of how it came to be
that evolution has such a neutral focus.

One possibility is that neutral theory works precisely be-
cause organisms contain sufficient information to target mu-
tations in areas that are less likely to be problematic—i.e.,
in areas where modifications are expected to occur and ac-
counted for. However, this presupposes the existence of
information within the cell to do the targeting. Neutral
theory cannot hoist itself up by its own petard to perform
this, and neither can neo-Darwinian selectionism.

Constructive Neutral Evolution (Stoltzfus, 2012), abbrevi-
ated CNE, is an attempt to get around this, but winds
up falling into the same trap. It aims to be more com-
prehensive in the small scale, specifically accounting for
complexity. It is interesting that the models of CNE show
how complexity can form, but leave out how those com-
plexities turned functional—it is merely assumed that they
often do. Interestingly, this mirrors the same process de-
scribed in this paper with earlier forms of neutral evolu-
tion, with researchers passively switching back-and-forth
between whether the theory only describes a process or
whether it is a comprehensive solution to the problem of
complexity.

A better research program for neutral theory is to recog-
nize the limitations of neutral theory’s role in evolution,
and determine the necessary conditions for neutral theory
to work. The most rigorous descriptions of what makes
evolution workable in a general sense focuses on the infor-
mation present in organisms (Marks II et al., 2013; Ewert
and Marks II, 2017; Dembski and Marks II, 2009; Bartlett,
2010; Dembsking and Marks II, 2010). As the Evolutionary
Informatics lab points out, “information makes evolution
possible” (Evolutionary Informatics Lab, 2019).

Ultimately, either neutral theorists need to say that this
introduction of information is beyond the reach of biology
(similar to the stance of Yockey (2000)) or, like Intelligent
Design, propose a valid source or mechanism for such infor-
mation to have been included into organisms (Meyer, 2009).
Eternally punting to mechanisms known not to be able to
produce the effect in question, however, does not make for
an effective research program in the long term.

Bartlett, J (2010). “Irreducible Complexity and Relative Ir-
reducible Complexity: Foundations and Applications”.
In: Occasional Papers of the BSG 15, pp. 1–10.

Bartlett, J (2017). “Evolutionary Teleonomy as a Unifying
Principle for the Extended Evolutionary Synthesis”. In:
Bio-Complexity 2017.2, pp. 1–7.

Dembski, W A and R J Marks II (2009). “Conservation of
Information in Search: Measuring the Cost of Success”.
In: IEEE Transactions on Systems, Man and Cybernet-
ics A, Systems and Humans 5.5, pp. 1051–1061.

Dembsking, W A and R J Marks II (2010). “The Search for
a Search: Measuring the Information Cost of Higher
Level Search”. In: Journal of Advanced Computational
Intelligence and Intelligent Informatics 14.5, pp. 475–
486.

Dietrich, M R (1994). “The Origins of the Neutral Theory
of Molecular Evolution”. In: Journal of the History of
Biology 27.1, pp. 21–59.

Evolutionary Informatics Lab (2019). “Frequently Asked
Questions”. In: Evolutionary Informatics Lab Website.
url: http://evoinfo.org/faq/.

Ewert, W and R J Marks II (2017). “Conservation of
Information in Coevolutionary Searches”. In: Bio-
Complexity 2017 (1), pp. 1–15.

Eyre-Walker, A and P D Keightley (2007). “The distribu-
tion of fitness effects of new mutations”. In: Nature Re-
views Genetics 8.8, pp. 610–618.

Kimura, M (1968). “Evolutionary Rate at the Molecular
Level”. In: Nature 217, pp. 624–626.

Marks II, R J et al. (2013). Biological Information: New
Perspectives. World Scientific.

Meyer, Stephen (2009). Signature in the Cell. HarperOne.
Sanford, J et al. (2007). “Using Computer Simulation to

Understand Mutation Accumulation Dynamics and Ge-
netic Load”. In: Lecture Notes in Computer Science
4488, pp. 386–392.

Stoltzfus, A (2012). “Constructive neutral evolution: explor-
ing evolutionary theorys curious disconnect”. In: Bi-
ology Direct 7.35. doi: 10.1186/1745- 6150- 7- 35.
url: https://biologydirect.biomedcentral.com/
articles/10.1186/1745-6150-7-35.

Yockey, H (2000). “Origin of Life on Earth and Shannon’s
Theory of Communication”. In: Computers and Chem-
istry 24.1, pp. 105–123.


