Q: Why do we humans have a hard time understanding, and
sometimes accepting, evolution? What, in your opinion, is the
major stumbling block?
A: Deep time is hard to grasp. I don't know that it or
any one thing could be called "the" major stumbling block. The major
stumbling block is that we're not quite ready, because we live in
a veil of tears, and we know that bad things happen to good people.
We're still desperate, many of us, to find factual answers out there
that would make us feel better in a psychological sense about some
of the cruel things that don't make sense in life. And that's a very
hard one to get through, I think. Once you come to terms with the
recognition that the answers to moral questions aren't out there in
nature, and you shouldn't be seeking them there, you have to seek
them inside yourself -- and that is the proper role of religion and
humanities -- then it ceases to worry. But it does worry many people.
And since it does, there are a whole set of issues that then
become very hard to accept, one of which is that most organisms are
bacteria. And there isn't a linear progressive pattern that pervades
evolution leading up to humans. Another is that humans are a tiny
little twig representing one species among so many millions on this
enormous arborescent tree of life. And a third is what we're talking
about now, that this tiny little twig of Homo sapiens represents
an eye blink of geological immensity.
I think they all go together, and they all represent our
unwillingness to give up on the notion that there is meaning out
there expressed in human terms, which is a kind of ultimate hubris.
I don't deny that there's meaning out there that we have to find.
But to think that the meaning of this immense complexity and variety
of life should be framed only in terms of one funny little primate
species … to think that it all exists because of us, or that its
meaning is framed in terms of us, that's an ultimate kind of arrogance
that I think is most unlikely to be correct in any sense.
Q: How does Darwin's theory rank among the great scientific
discoveries of all time?
A: Sigmund Freud made a famous and often repeated comment
that the few truly great revolutions in the history of science all
have the common property that they not only reform our concept of the
physical universe -- which obviously they do or we wouldn't call them
revolutions -- but that they also ironically knock human arrogance
off one pedestal after another of our previous beliefs and our own
self importance. And clearly, that's where Darwin ranks so highly.
Freud said that there were really two great revolutions. The first
that we associate with Copernicus, Newton, and Galileo that taught us
that we weren't living on the central body of a limited universe. And
that Darwin's was the second that taught us that we were not separately
created in the image of a benevolent deity, but were part of a history
of genealogical connectivity of all living things.
Now, in an odd sense, we know how contentious the first revolution
was; we know the story of Galileo. But contrary to popular understanding,
the church made its peace with Galileo. They may not have taken his
books off the index or officially exonerated him until recently. But
a few years after his death it was not a hot issue anymore because
people knew the earth goes around the sun, and that's all there was
to it. And it wasn't going to do much good to try and base a theology
on getting nature backwards.
But the way I like to put it, I don't think that revolution
was as important as Darwin's, because it's about real estate. The
Darwinian revolution is about essence; it's deeper. The Darwinian
revolution is about who we are, it's what we're made of, it's what
our life means insofar as science can answer that question. Science
cannot answer all aspects of that question. It can't tell us what our
life means ethically. It can't tell us what we are meant to do as
moral creatures. But insofar as science can understand what we're
made of, and what we're related to, the Darwinian revolution
completely revised our ideas about who we are, and what we're related
to, and how long we've been here, and why we're on this earth --
again, in limited ways that science can apprehend or comprehend
So it, in many ways, was the singularly deepest and most
discombobulating of all discoveries that science has ever made. And
that it is so factually firm and so well documented merely makes it
all the more salient, because it isn't just a conjecture; it's an
entire reconstruction of our concept of ourselves and who we are that
is as well documented as anything we've ever learned in science. So
that does give the Darwinian revolution a unique status.
But, again, we shouldn't take it too far. Science, as any
enterprise, has a limited frame. Science is an enterprise that deals
with the factual world as we understand it and as we come to understand
it better. And it deals with why the factual world works as it does,
and not some other way in which it might work. That's roughly fact
and theory, but there are many questions about human life and human
nature that science can't answer. Science can't answer ethical
questions. Science can't answer questions about meaning in the
spiritual or theological sense. And we shouldn't pretend that it can.
Q: Can you talk about evolution as an amoral process?
A: I don't think there's moral messages of any kind in
nature. The most you can get out of nature is an understanding of
how the world operates, which is certainly material you want to
factor into any moral debate you're going to have. It's not going
to answer moral questions for you.
All that happens in evolution, at least under Darwinian natural
selection, is that organisms are struggling in some metaphorical
and unconscious sense for differential reproductive success, however
it happens. Some succeed; most fail and die. Some succeed by things
we don't happen to like, like killing others. Some succeed in it by
things we do like, such as cooperation. And others succeed by inflicting
enormous pain and harm upon others, including human beings. So we
don't like it. But it has nothing to do with nature's ways. If
bacterium or a virus gains differential reproduction success by
making us sick and exploiting our bodies, then so be it.
Q: How can chance mutations result in adaptations that seem
to be purposefully designed?
A: It's a common phrase that natural selection is chance
and necessity. It goes back to the title of a book by the great
French biologist Jacques Monod. But it's not really correct, because
the chance part is not natural selection. Natural selection is
actually a locally deterministic force.
If you want to say the Darwinian evolution has a component of
chance, and a component of local necessity, that's quite accurate.
But the basic argument goes like this: Because natural selection
doesn't make anything, natural selection is an eliminative force.
Natural selection can only differentially preserve certain
variations in a spectrum of variation within a species. Now some
other process produces that variation; ultimately it's mutation.
And mutation is spread around through recombination and sexual
But because the causes of genetic mutation are occurring at the
level of the gene, and bear no reference to the adaptive design of
organisms, the variation among the organisms produced by mutation
bears no relationship to what's for the good of organisms. So it's
not random in the mathematical sense of flipping a coin and getting
50-50 [chance]. All we mean is that the variation which provides
the fuel for natural selection occurs without reference to those
characteristics that would be useful for an organism.
For example, if you have a bunch of elephants living in Siberia,
and it's getting cold because there's an ice sheet advancing,
there's going to be another Ice Age, you're going to have elephants
with different amounts of hair on their bodies. But there isn't any
internal force that produces more hair because that would be a good
thing. You just have variation among these different elephants, and
that's what we call random with respect to the direction of natural
selection. And then you have the second force, which is natural
selection, which is not necessity or determinism on a global scale.
Natural selection doesn't make overall more progressive or better
organisms; natural selection makes locally adapted organisms.
If you go back to that analogy, if you have a bunch of elephants
and it's getting colder, on average, -- this is statistical
phenomenon, not every time. After all, the hairiest elephant can
fall into a crevasse and die or be sterile and have no kids. But
it's a statistical phenomenon that elephants with more hair are
going to leave more surviving offspring. And that's natural selection.
Q: Do scientists and the lay public sometimes misunderstand
each other around evolution as conjecture, or around how much is
A: Scientists and the lay public often misunderstand
each other in the same sense that people who have deep technical
knowledge about any subject tend not to talk about it very well
to lay people. They often get into confusions. But I don't know
that it's any worse for science than for others. There is obviously
a particular context, because in the United States -- uniquely in
the Western world, I might add -- there is a politically motivated
bunch of folks out there who have a certain amount of local power,
even though they keep losing court cases, who for their own political
reasons are trying to push anti-evolutionism.
But putting that aside -- which has very little to do with the
content of science, though it's an interesting sociopolitical issue
in American history -- I don't know what to say, except that as a
factual proposition, evolution is about as well-documented as
anything we know very broadly in science; that there is a tree of
life, that all organisms are tied by genealogical connectivity, that
the history of life is, to use Darwin's words, "descent with
modification." I would say that's as well known as that the earth
goes around the sun, and not vice-versa.
Now there are all number of details that we don't know, because
you're dealing with an enormously complex narrative history of life
that often doesn't leave evidence of particular highways and byways.
Just as I can't give you a list of every soldier who fought at the
Battle of Marathon, but I don't doubt there was such a battle, I can't
tell you every species of brachiopod that died out in the Permian
extinction, but I can be pretty confident that large numbers of them
So I think we're very confident about the basic factuality of
evolution. But there's so much we don't know about particulars of
detailed pathways, and there's a lot we need to learn about mechanisms.
But that's true of all science. Science is a continually self-correcting
enterprise that doesn't always move triumphantly forward, but somehow
works its way to a better understanding of a pretty complex factual
reality out there.
Q: How much do we owe who we are today, our bodies and our
beings, to the 4 billion year history of environments and environmental
A: Evolution is the only process behind the construction
of our bodies, in a biological sense. Clearly all the sciences are
involved. The periodic table explains the elements that we're made
out of. Physics gets to the particles. But if you want to talk about
the history of life, that subject is evolution, the distinctive
characteristics of this one funny little primate species that is us,
or a function of that history. So evolutionary biology is the right
subject to consult.
We're basically a pretty ordinary mammal, with one absolutely
stunningly remarkable and powerful invention -- what we call, for
better or worse, "consciousness." But it's important not to mistake
the power of that invention, which is undoubted -- I don't think
anything else has ever happened in the history of evolution that
has so quickly given one funny little species such power over a
planet or over other living things. But you mustn't confuse the
impact of something with its fundamental mystery. It still remains
an aspect of evolutionary history that consciousness enables us
to do all sorts of things that were not anticipated or not part
of the actual reason why it all happened. It just adds to the
interest. But there it is.
Q: How do you help students understand the importance of the
earth's history and changing environments to evolution?
A: The basic theory of natural selection talks not about
predictable universal progress, or any inherent direction of
evolution. It's only a theory of adaptation to changing local
environments. That's really all it is. The parasite that becomes
morphologically simplified, living inside the body of its host,
is as well adapted to its environment as the complex bird flying
through the air. That's all it is: a theory of adaptation to
changing local environments.
Now because the history of the earth, its four-and-a-half
billion years, is a story of environmental change -- a story of
mountains building and seas moving in and out, and ice ages coming
and going -- the story of life history, insofar as it's regulated
by natural history, is a constant interplay and dance back and
forth. Environments change; creatures change to match those
It's not an automatic, mechanical process. Because by
environment we just don't mean it gets colder and an animal
gets hair. Environment is a complex construction that includes
the other organisms that share it with you. When you adapt to
your environment, that environment isn't only the climate and
the mountains and the oceans; it's also the other organisms
in that world.
In the same sense that human history is wonderfully complex
and unpredictable, because you never know when the next river
is going to break through, the next army is going to invade,
the history of life is the same way. It's a constant process
of adaptation by natural selection to changing local
environments. And the vector of those environmental changes
through time is effectively random. That makes the history
of life itself unpredictable, but still eminently documentable.