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Colloquium
Intervening in evolution: Ethics and actions
Paul R. Ehrlich*
Department of Biological Sciences, Stanford University, Stanford, CA 94305
Biologists should help to guide a process of cultural evolution in
which society determines how much effort, if any, is ethically
required to preserve options in biological evolution. Evolutionists,
conservation biologists, and ecologists should be doing more
research to determine actions that would best help to avoid
foreclosing evolutionary options.
There is no question that Homo sapiens, in addition to causing
the sixth major spasm of biotic extinction (1-4), is also
altering the course of evolution for millions of years in the future.
Many of the important issues raised by that alteration have been
beautifully laid out by Norman Myers (5~. Here I explore three
overarching questions. The first is a fundamental hack~ro~,nr1
one: Where do ethics come from? This leads to the second.
Considering that just two or three human generations are
dramatically changing the biotas that will comprise a major
portion of the environment of tens of thousands of future
generations, what ethical obligations might this impose on
scientists to respond in various ways? And the third is: If we are
ethically obligated, what might scientists do to be more effective
in informing society of its options in this area? These are
complex issues; I deal only with the tip of the iceberg here.
The ethical questions about intervention in the evolutionary
process are very similar to questions about the closely related
issue of the preservation of biodiversity (2~. Most of us believe
that people in the future should be able to obtain from biodi-
versity a wide variety of esthetic pleasures, ecosystem goods, and,
especially, ecosystem services (6~. Humanity is now faced with
the prospect of a continuing loss of the populations (7) and
species (8) that supply those values. But, beyond this loss, society
is taking actions that will modify both the rate of evolutionary
regeneration of populations and species and the nature of the
replacements produced. Our acceleration of the rate of extinc-
tions and modification of the evolutionary process immediately
raises an ethical issue long recognized by economists and others
(9) as that of "intergenerational equity." The basic question is:
At what rate, if any, is it moral for the current generation to
discount the future? This question, in turn, leads us to the much
more general questions of the origins and nature of ethical
systems.
Where Do Ethics Come From?
Many people, following (most famously) Plato (10) and Kant
(11), believe that, in essence, there exists a universe of ethics
quite independent of the universe in which we dwell (or,
equivalently, there is a god with all of the answers). To those
holding that belief, answers to questions about the ethics of
redirecting evolution have always been "out there"; our task is
simply to discover them. Others believe that ethics can be derived
directly from the evolutionary process itself that, basically,
whatever behavior has evolved is good because it evolved (for an
overview, see ref. 12~. They contend that one can determine what
ought to be from what is (a contention that is often called by
opponents of this view "the naturalistic fallacy"~. I, and many
~ ~ .
others, take a third view (13~: there is no extrinsic source of
ethics, but human beings have evolved the capacity to hold and
www.pnas.org/cgi/doi/10.1 073/pnas.091 093898
share values. Natural selection has, however, not helped us much
in deciding what values to hold. The content of ethical systems-
the things that a human being believes are right or wrong, moral
or immoral is assumed in this view to be almost entirely a
product of cultural evolution.
Our dilemma of whether or how to change ethical systems so
they can deal with human alteration of evolutionary processes
assumes that cultural evolution is the primary source of values.
After all, if there were an independent ethical universe we could
tap into, it seems unlikely that ethics would differ as much as they
do from culture to culture and time to time. A couple of centuries
ago, slavery was ethically acceptable, as it had been since the
dawn of history. It still is in some subcultures. An example, closer
to the topic of this symposium, of cultural evolution that has
altered ethics over the last few centuries is the widening of the
circle of caring: the attribution of rights first to all human beings
(as opposed to only some group of kin or pseudokin), then to
domestic animals, then to charismatic wild animals, and even-
tually to all organisms and ecosystems. Furthermore, one can
observe ethics evolving all of the time at a rate that cannot be
explained by genetic evolution. It's happening at this meeting.
No one was expressing concern about changing evolutionary
trajectories even two decades ago. One could, of course, argue
that the external ethical universe exists, and it is our communi-
cation with that universe or a deity that is continually culturally
evolving. But that does not seem to be a very informative
approach if we wish to understand the evolution of ethical
systems. On the other hand, I see no sign that the process of
evolution itself has provided many, if any, standards to undergird
a system of ethics, including ethics about the maintenance of that
process.
The evolution of ethics appears to be a product of a complex
brain that evolved for, among other things, dealing with other
smart individuals living in the same social groups. The roots of
ethics seem to trace to the evolution of empathy the ability to
imagine another's viewpoint. Being able to consider the mental
processes of members of one's group and relate emotionally to
their states doubtless had a reproductive payoff and probably was
a predisposition created by natural selection. But much of the
behavior that "evolutionary psychologists" (e.g., refs. 14 and 15)
and others attribute to genetic predispositions clearly can't be
the direct result of biological evolution we haven't the genes to
do the job. Genes cannot incorporate enough instructions into
the brain's structure to program an appropriate reaction to every
conceivable behavioral situation, or even very large numbers of
them. Here is an instance where a little bit of reductionist
analysis suggests the hopelessness of seeking a genetic reduc-
tionist explanation of most of human behavior, including our
ethical behavior related to the course of evolution (13~. There
are something on the order of 30,000 loci in the genome, whereas
there are roughly 100 to 1000 trillion connections (synapses)
between over a trillion nerve cells in our brains. That's at least
This paper was presentecl at the National Acaclemy of Sciences colioqulum, "The Future of
Evolution," held March ~ 6-20, 2000, at the Arnold and Mabel Beckman Center in Irvine, CA.
*E-maii: pre~ieiancl.stanforcl.eclu.
PNAS 1 May 8, 2001 1 vol. 98 1 no. 10 1 5477-5480
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one billion synapses per locus, even if every locus in the genome
contributed to creating a synapse. Clearly, those connections can
be only partially specified by genetic information; the environ-
ment and cultural evolution must play a very large, often
dominant role in establishing the complex neural networks that
modulate human behavior. To put it in shorthand, we could be
said to have a "gene shortage," a point lost on popular writers
in their enthusiasm to find "a gene" for every human behavioral
characteristic (e.g., refs. 16 and 17~.
Scientific Response to Human Modification of Evolutionary
Trajectories
In this symposium, we are starting a dialogue over the ethical
issues of human alteration of the future course of evolution,
which can be viewed as an extension of the dialogue that already
includes decision makers and the general public in discussions
over human responsibility for abating the extinction crisis (18~.
I believe we can't look either to a deity or to evolution itself for
answers. It is up to the human community to decide what the
ethical course is, and to take whatever steps are then deemed
ethically appropriate. Thus the answer to my second broad
question seems to be that it is up to us as scientists to determine
what are our own ethical obligations, and to help society at large
to make its decisions.
Achieving some level of consensus on those obligations will
not be an easy task. At one extreme, some will advise restoring
huge areas of wilderness to provide evolutionary opportunities
for continuation of megavertebrate diversification. That, clearly,
is the view of those involved in the Wildlands Project (e.g., ref.
19) and it's where I would come down emotionally if I could
ignore the practical and ethical complexities of its implementa-
tion in most parts of the world. At the other extreme are the
technological optimists who assume that genetic engineers will
soon be able to produce any needed biodiversity to order and so
see no reason to preserve what is left or worry about future
evolutionary trajectories. They have a very high rate of discount-
ing the future, because they assume that coming generations will
be sufficiently richer and more technologically adept to solve any
problems that altered evolution can present. This latter view will,
of course, appeal to many in our gadget-oriented society, espe-
cially those who believe their financial security will be best
protected under a "business as usual" scenario. And between
those at the extremes (who will at least have considered the
issue) will be the vast majority of humanity, people who simply
see little reason to value most of biodiversity.
In the coming ethical debate, we must be extremely careful to
take a broad view of the "human community" and not subcon-
sciously assume that everyone shares the views of the community
of evolutionary biologists, ecologists, and conservationists from
rich countries. There is, understandably, considerable resent-
ment in developing countries over what they view as a preference
among conservation biologists for locking away land to protect
biodiversity (and presumably future evolutionary options) with-
out considering the present, sometimes dire needs of local
communities or indeed of regions or even entire poor nations
(20, 21~. Choices will often have to be made between protecting
the health and welfare of human beings living today, and risking
those of future generations; evaluating such trade-offs and
deciding on courses of action is likely to be difficult. For instance,
revenue from logging a tropical forest might be used to help poor
people living near the forest today. Would it be worth forgoing
that revenue to preserve the forest as a potential generator of
diversity that might improve the lives of people 2000 or 200,000
generations in the future? How are values to be assigned, and
who should make this sort of decision? Is there any ethical need
to consider the effects of today's actions that far or farther in the
future? Could or should we strive to create such an ethical
imperative? Can we possibly know enough to sensibly fashion an
5478 1 www.pnas.org/cgi/doi/10.1073/pnas.091093898
evolutionary ethic? Is it reasonable to imply an evolutionary
discount rate of zero? Those who, like me, personally believe
attention should be paid to the consequences of our actions for
the long-term future must develop our arguments very carefully
and not assume that there is a self-evident ethical need to do so.
Evolutionists, ecologists, and systematists can begin address-
ing these complex issues in four ways: through public education,
interacting with those in other disciplines and walks of life,
changing our research agendas, and working to find practical
ways of influencing the evolution of ethics. Considering the long
debate over the preservation of biodiversity (e.g., in the United
States, continuing battles over the Endangered Species Act), it
is clear to me that scientists concerned with answering the sorts
of questions posed above and developing an ethics of preserving
evolutionary processes will be caught in one of many mismatches
in rates of cultural evolution (13~. The speed at which society is
changing the evolutionary prospect seems fated to remain much
more rapid than the rate at which society is developing ethics to
deal with the challenges that change may present. In this
situation, the first and most obvious thing that we should do is
alert the public and decision makers to the possible problem. I
hope the colloquium on The Future of Evolution will mark the
beginning of an effort by the concerned scientific community to
do just that. Ecologists have gradually begun to realize that their
responsibilities to society extend far beyond simply doing first-
rate science and reporting the results in the scientific literature
(22, 23~. Evolutionists and systematists have lagged behind
ecologists in awareness and action, but now is the time to start
closing the gap (24~.
Despite the uncertainties that are inherent in science, on issues
of great importance to humanity, scientists must keep the public
apprised of the latest consensus view of the pertinent scientific
community (including recommendations for possible policy
changes). Uncertainties, of course, should be made explicit in
such communications, and when a scientist expresses a personal
opinion diverging from the consensus, it should be clearly
labeled as such. The idea that science should (or can) be
value-free, a view expressed by several researchers recently (e.g.,
23) and widely held in society, simply reflects a failure in the
education of both scientists and members of the general public.
The same can be said for the opinion that scientists should not
make predictions about such things as future evolutionary
trajectories because they may not be accurate, or the idea that
one should wait until "uncertainties are resolved." Scientists, of
course, make value judgments all of the time in their choice of
projects (what is "worthwhile" investigating), choice of methods
(e.g., how much disturbance of an ecosystem or injury to
organisms would be justified by the information gained), and
interpretation of results ("the most important conclusion from
this study is . . A. We cannot avoid such judgments, because
being steeped in values is an important part of being human. The
relative objectivity of science comes primarily not from the
efforts we all make to be objective, but from adherence to rules
(honesty, full disclosure of procedures, attempts to falsify one's
own hypotheses), the adversarial nature of the enterprise (peer
review, replication by others, eventual rewards for showing the
paradigm has no clothes), and the existence of nature (an
assumption) to serve as a final arbiter.
Making predictions is an important part of science, and a
major challenge in the area of evolution is to make the best
possible predictions on what human intervention means to the
evolutionary process. We must seek ways that some of those
predictions can be tested in the relatively short term. When the
predictions are not fulfilled (they frequently will not be), the
reasons for the failure should provide an entree into finding just
what part of the system was inadequately understood. And, of
course, one thing that separates science from other ways of
knowing is that uncertainties are never fully resolved. At best, the
Ehr~ich
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community agrees that the uncertainties are minimal (although
many a paradigm has crashed after such agreement), and
individual scientists will always differ on the degree of trust they
put in a given conclusion. Our credibility should rest on the
openness with which we explain the uncertainties, our readiness
to change conclusions and recommendations as new data come
in, being clear on how our own views relate to the scientific
consensus, and persistence in telling politicians that neither they
nor anyone else can supply absolute certainty on a scientific
issue. Credibility cannot and should not rest on an implicit notion
that "science" in the abstract can be trusted.
A second way that evolutionists, ecologists, and systematists
can contribute fully to the cultural evolution of ethics relating
to future biological evolution is to participate increasingly in
interdisciplinary research and interaction with people with
different backgrounds and attitudes. We will wish to outline
for society the likely consequences of alternative courses of
action (or inaction) and, at least by implication, advocate
certain courses of action. But without input from economists,
political scientists, legal scholars, the business community, and
others, some of the alternatives presented may at best have
little chance of acceptance by society as a whole, or at worst
produce results counter to those intended. Remember, it is not
for us to dictate what society wants, but rather to interact
vigorously with the public in an attempt to achieve ends that
both make sense scientifically and are socially and politically
feasible. As I indicated, in virtually all cases, society will be
faced with increasingly difficult choices among alternate
courses of action. Many will involve trade-offs between
desirable outcomes, and scientists must help to clarify them.
As individuals, not as scientists, we also may advocate our
own preferences. The latter is important; although we can-
not dictate a course of action to the rest of society, neither
should we be disenfranchised when it comes to social decision
making.
Third, beyond improving scientific outreach, we should be
reexamining our research agendas so that they yield as much
information as possible pertinent to evaluating the scale of
anthropogenic impacts on the future course of biotic evolu-
tion, and attempting to find ways to ameliorate those consid-
ered potentially the most serious—as Norman Myers has been
urging for more than a decade. The papers presented in this
colloquium indicate that this process is finally underway, and
much recent work is, perhaps serendipitously, pertinent to
major issues. For instance, the question of whether isolation is
the key to geographic speciation (25-27) or whether differ-
ences in selection pressures are equally or more important (28)
is now being reexamined in some detail (29~. The answer to
that question could be important if society decides that it
wishes to encourage the continued generation of diversity. If
different selection pressures are paramount, then the un-
planned trend toward reducing once-continuous tracts of
habitat into many isolated but similar fragments will not
enhance speciation to the degree that some may hope. In any
I. Myers, N. (1979) The Sinking Ark (Pergamon, New York).
2. Ehrlich, P. R. & Ehrlich, A. H. (1981) Extinction: The Causes and Consequences
of the Disappearance of Species (Random House, New York).
3. Sepkoski, J. J., Jr. (1986) in Patterns and Processes in the History of Life, eds.
Raup, D. M. & Jablonski, D. (Springer, Berlin), pp. 277-295.
4. Leakey, R. & Lewin, R. (1995) The Sixth Extinction: Patterns of Life and the
Future of Humankind (Doubleday, New York).
5. Myers, N. (1996) Environmentalist 16, 37-47.
6. Daily, G. C. (1997) Nature's Services (Island Press, Washington, DC).
7. Hughes, J. B., Daily, G. C. & Ehrlich, P. R. (1997) Science 278, 689-692.
8. Wilson, E. O. (1992) The Diversity of Life (Harvard Univ. Press, Cambridge,
MA).
9. Costanza, R. (1991) Ecological Economics: The Science and Management of
sustainability (Columbia Univ. Press, New York).
Ehrlich
case, we don't know enough to establish with confidence
conservation priorities aimed to influence future evolutionary
effects.
One example of a potentially fruitful research agenda is that
of the new discipline of countryside biogeography (30-32~.
Ecologists and conservation biologists have recently started to
realize that there is no longer such a thing as an undisturbed
habitat no pristine systems to study. They have begun to focus
more attention on the ecology of organisms in the vast areas that
have already experienced substantial anthropogenic distur-
bance. The goals of countryside biogeography include determin-
ing what elements of biodiversity are best able to persist in
altered habitats, establishing the relationship between degree of
intensification of land use and an area's conservation value,
evaluating the importance of remnant habitat to the delivery of
ecosystem services, and finding ways to enhance the conserva-
tion/service-delivery value of human-dominated countrysides.
This work could also provide a foundation for what we might call
"countryside evolution," which could examine the possible
impact of various patterns of habitat alteration on evolutionary
trajectories and seek ways to enhance the evolutionary potential
of communities persisting in areas heavily impacted by human
activities.
It is clear that the activities of Homo sapiens are dramatically
altering the future course of biological evolution, and, if current
trends continue, the degree of alteration is likely to accelerate
and lead to substantial discontinuities. But the possible conse-
quences of this for humanity are much less obvious, so it is hard
to present specific options except self-evident ones such as: "if
society wishes to preserve opportunities for continued diversi-
fication of large animals in groups such as the big cats, horses,
antelopes, and our closest primate relatives, more effort should
be put into the conservation of large tracts of wilderness." More
broadly and more importantly—environmental scientists to-
day can simply recommend that those whose values include a
concern for the options of distant future generations take more
care when meddling in a process billions of years old, which,
when severely perturbed, could change the biosphere dramati-
cally for millions of years in unpredictable ways. We can and
should do better.
Fourth, in addition to adding to the knowledge base that society
will need in its decision-making, scientists should participate in the
hard work of outlining feasible ways of accomplishing changes they
deem advisable. Although the mismatch between the rate at
which society is altering the evolutionary future and the rate at
which it is recognizing, evaluating, and taking action on the
issue is severe, we should not despair. The rate at which our
society evolves new ethics to deal with various aspects of the human ~
predicament, including the evolutionary dilemma, can be acceler- ,
ated. Cultural evolution clearly can be directed (13, 33), but a If
determined effort by a large and diverse sample of people is 0
required. This symposium must be just a beginning.
I thank Gretchen C. Daily, Anne H. Ehrlich, Jessica Hellmann, and
Taylor Ricketts for helpful comments on the manuscript.
10. Honderich, T. (1995) The Oxford Companion to Philosophy (Oxford Univ. Press,
Oxford), pp. 683-686.
11. Kant, I. The Metaphysics of Morals, trans. Mary Gregor (1996) (Cambridge
Univ. Press, Cambridge, U.K.).
12. Nitecki, M. H. & Nitecki, D. V. (1993) Evolutionary Ethics (State Univ. of New
York Press, Albany, NY).
13. Ehrlich, P. R. (2000) Human Natures: Genes, Cultures, and the Human Prospect
(Island Press, Washington, DC).
14. Barkow, J. H., Cosmides, L. & Tooby, J. (1992) The Adapted Mind:
Evolutionary Psychology and the Generation of Culture (Oxford Univ. Press,
New York).
15. Geary, D. C. (2000) Psychol. Bull. 126, 55-57.
16. Hamer, D. & Copeland, P. (1998) Living with Our Genes: Why They Matter More
Than You Think (Doubleday, New York).
PNAS 1 May 8, 2001 1 vol 98 1 no 10 1 5479
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17. Ridley, M. (1999) Genome: The Autobiography of a Species in Twenty-Three
Chapters (HarperCollins, New York).
18. Soule, M. E. & Lease, G. (1995), Reinventing Nautre: Responses to Postmodern
Destruction (Island Press, Washington, DC).
19. Soule, M. E. (1999) Wildlands 9, 38-46.
20. Guha, R. (1989) Environ. Ethics 11, 71-83.
21. Guha, R. (1997) Ecologist 27, 14-21.
22. Bazzaz, F., Ceballos, G., Davis, M., Dirzo, R., Ehrlich, P. R., Eisner, T., Levin,
S., Lawton, J. H., Lubchenco, J., Matson, P. A., et al. (1998) Science 282, 879
(lett.).
23. Kaiser, J. (2000) Science 287, 1188-1192.
24. Ehrlich, P. R. (1997) A World of Wounds: Ecologists and the Human Dilemma
(Ecology Institute, Oldendorf/Luhe, Germany).
5480 1 www.pnas.org/cgi/doi/10.1073/pnas.091093898
25. MacArthur, R. H. & MacArthur, J. W. (1961) Ecology 42, 594-598.
26. Mayr, E. (1942) Systematics and the Origin of Species (Columbia Univ. Press, New York).
27. Mayr, E. (1963) Animal Species and Evolution (Harvard Univ. Press, Cam-
bridge, MA).
28. Ehrlich, P. R. & Raven, P. H. (1969) Science 65,1228-1232.
29. Brown, K. (1999) New Sci. 20, 46-49.
30. Daily, G. C. (2000) in Nature and Human Society: The Quest for a Sustainable
World, ed. Raven, P. H. (Natl. Acad. Press, Washington, DC).
31. Daily, G. C., Ehrlich, P. R. & Sanchez-Azofeifa, A. (2001) Ecol. Appl. 1, 1-13.
32. Ricketts, T., Daily, G. C., Ehrlich, P. R. & Fay, J. P. (2001) Conserv. Biol., in
press.
33. Ornstein, R. & Ehrlich, P. (1989) New World/New Mind: Moving Toward
Conscious Evolution (Doubleday, New York).
Ehrlich
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National Academy of Sciences Colloquium
The Future of Evolution
March ~ 6-1 9, 2000
Program
Friday, March 17, 2000
Session ~
Norman Myers, Oxford University, and Andrew Knoll, Harvard University
Introduction
David Jablonski, University of Chicago
Lessons from the Past: Evolutionary Impacts of Mass Extinctions
Doug Erwin, National Museum of Natural History, Smithsonian Institution
Lessons from the Past: Biotic Recovery from Mass Extinctions
Alan Templeton, Washington University, St. Louis
Disrupting Evolutionary Processes
Michael Gilpin, University of California, San Diego
Metapopulation Dynamics
David Western, Wildlife Conservation Society and African Conservation Centre
Ecosystem Survival in a Human-Dominated World
Session I!
Mike Rosenzweig, University of Arizona
Speciation: Past, Present, and Future
Nancy Knowlton, University of California, San Diego
Reef Ecosystems of the Future
Jeremy Jackson, University of California, San Diego
Biodiversity Decline in the Marine Realm
Fakhri Bazzaz, Harvard University
Plant Biology of the Future
Richard Cowling, University of Cape Town
Rapid Plant Diversification: Planning for an Evolutionary Future
Hal Mooney, Stanford University
Alien Invasions and Mixing of Biotas
David Tilman, University of Minnesota
The Vacant Niches of Human-Dominated Ecosystems
Paul Ehrlich, Stanford University
Intervening in Evolution: Ethics and Actions
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Saturday, March 1S, 2000
Session Il!
Discussion Leader, Peter Kareiva, University of Washington
Panel I: Ecological Modeling of Current and Future Diversity Threats
Discussion Leader, Russ Graham, Denver Museum of Natural History
Panel II: Lessons from the Pleistocene
Discussion Leader, David Woodruff, University of California, San Diego
Panel III: Decline of Biomes and Biotas
Discussion Leader, Michael Novacek, American Museum of Natural History
Panel IV: Scenarios for Recovery
Sunday, March 19, 2000
Session IV
Panel Reports
Session V
Conclusions
Representative terms from entire chapter:
evolutionary trajectories
