The GOD Delusion (21 page)

* If
you find that surprising, you may be suffering from northern hemisphere
chauvinism, as described on page 114-15.

Two
main explanations have been offered for our planet's peculiar
friendliness to life. The design theory says that God made the world,
placed it in the Goldilocks zone, and deliberately set up all the
details for our benefit. The anthropic approach is very different, and
it has a faintly Darwinian feel. The great majority of planets in the
universe are not in the Goldilocks zones of their respective stars, and
not suitable for life. None of that majority has life. However small
the minority of planets with just the right conditions for life may be,
we necessarily have to be on one of that minority, because here we are
thinking about it.

It
is a strange fact, incidentally, that religious apologists love the
anthropic principle. For some reason that makes no sense at all, they
think it supports their case. Precisely the opposite is true. The
anthropic principle, like natural selection, is an
alternative
to the design hypothesis. It provides a rational, design-free
explanation for the fact that we find ourselves in a situation
propitious to our existence. I think the confusion arises in the
religious mind because the anthropic principle is only ever mentioned
in the context of the problem that it solves, namely the fact that we
live in a life-friendly place. What the religious mind then fails to
grasp is that two candidate solutions are offered to the problem. God
is one. The anthropic principle is the other. They are
alternatives.

Liquid
water is a necessary condition for life as we know it, but it is far
from sufficient. Life still has to originate in the water, and the
origin of life may have been a highly improbable occurrence. Darwinian
evolution proceeds merrily once life has originated. But how does life
get started? The origin of life was the chemical event, or series of
events, whereby the vital conditions for natural selection first came
about. The major ingredient was heredity, either DNA or (more probably)
something that copies like DNA but less accurately, perhaps the related
molecule RNA. Once the vital ingredient - some kind of genetic molecule
- is in place, true Darwinian natural selection can follow, and complex
life emerges as the eventual consequence. But the spontaneous arising
by chance of the first hereditary molecule strikes many as improbable.
Maybe it is - very very improbable, and I shall dwell on this, for it
is central to this section of the book.

The
origin of life is a flourishing, if speculative, subject for research.
The expertise required for it is chemistry and it is not mine. I watch
from the sidelines with engaged curiosity, and I shall not be surprised
if, within the next few years, chemists report that they have
successfully midwifed a new origin of life in the laboratory.
Nevertheless it hasn't happened yet, and it is still possible to
maintain that the probability of its happening is, and always was,
exceedingly low - although it did happen once!

Just
as we did with the Goldilocks orbits, we can make the point that,
however improbable the origin of life might be, we know it happened on
Earth because we are here. Again as with temperature, there are two
hypotheses to explain what happened - the design hypothesis and the
scientific or 'anthropic' hypothesis. The design approach postulates a
God who wrought a deliberate miracle, struck the prebiotic soup with
divine fire and launched DNA, or something equivalent, on its momentous
career.

Again,
as with Goldilocks, the anthropic alternative to the design hypothesis
is statistical. Scientists invoke the magic of large numbers. It has
been estimated that there are between 1 billion and 30 billion planets
in our galaxy, and about 100 billion galaxies in the universe. Knocking
a few noughts off for reasons of ordinary prudence, a billion billion
is a conservative estimate of the number of available planets in the
universe. Now, suppose the origin of life, the
spontaneous arising of something equivalent to DNA, really was a quite
staggeringly improbable event. Suppose it was so improbable as to occur
on only one in a billion planets. A grant-giving body would laugh at
any chemist who admitted that the chance of his proposed research
succeeding was only one in a hundred. But here we are talking about
odds of one in a billion. And yet . . . even with such absurdly long
odds, life will still have arisen on a billion planets - of which
Earth, of course, is one.
⁶⁹

This
conclusion is so surprising, I'll say it again. If the odds of life
originating spontaneously on a planet were a billion to one against,
nevertheless that stupefyingly improbable event would still happen on a
billion planets. The chance of finding any one of those billion
life-bearing planets recalls the proverbial needle in a haystack. But
we don't have to go out of our way to find a needle because (back to
the anthropic principle) any beings capable of looking must necessarily
be sitting on one of those prodigiously rare needles before they even
start the search.

Any
probability statement is made in the context of a certain level of
ignorance. If we know nothing about a planet, we may postulate the odds
of life's arising on it as, say, one in a billion. But if we now import
some new assumptions into our estimate, things change. A particular
planet may have some peculiar properties, perhaps a special profile of
element abundances in its rocks, which shift the odds in favour of
life's emerging. Some planets, in other words, are more 'Earth-like'
than others. Earth itself, of course, is especially Earth-like! This
should give encouragement to our chemists trying to recreate the event
in the lab, for it could shorten the odds against their success. But my
earlier calculation demonstrated that even a chemical model with odds
of success as low as one in a billion would
still
predict
that life would arise on a billion planets in the universe. And the
beauty of the anthropic principle is that it tells us, against all
intuition, that a chemical model need only predict that life will arise
on
one
planet in a billion billion to give us a
good and entirely satisfying explanation for the presence of life here.
I do not for a moment believe the origin of life was anywhere near so
improbable in practice. I think it is definitely worth spending money
on trying to duplicate the event in the lab and - by the same token, on
SETI, because I think it is likely that there is intelligent life
elsewhere.

Even
accepting the most pessimistic estimate of the probability that life
might spontaneously originate, this statistical argument completely
demolishes any suggestion that we should postulate design to fill the
gap. Of all the apparent gaps in the evolutionary story, the origin of
life gap can seem unbridgeable to brains calibrated to assess
likelihood and risk on an everyday scale: the scale on which
grant-giving bodies assess research proposals submitted by chemists.
Yet even so big a gap as this is easily filled by statistically
informed science, while the very same statistical science rules out a
divine creator on the 'Ultimate 747' grounds we met earlier.

But
now, to return to the interesting point that launched this section.
Suppose somebody tried to explain the general phenomenon of biological
adaptation along the same lines as we have just applied to the origin
of life: appealing to an immense number of available planets. The
observed fact is that every species, and every organ that has ever been
looked at within every species, is good at what it does. The wings of
birds, bees and bats are good at flying. Eyes are good at seeing.
Leaves are good at photo-synthesizing. We live on a planet where we are
surrounded by perhaps ten million species, each one of which
independently displays a powerful illusion of apparent design. Each
species is well fitted to its particular way of life. Could we get away
with the 'huge numbers of planets' argument to explain all these
separate illusions of design? No, we could not, repeat
not.
Don't
even think about it. This is important, for it goes to the heart of the
most serious misunderstanding of Darwinism.

It
doesn't matter how many planets we have to play with, lucky chance
could never be enough to explain the lush diversity of living
complexity on Earth in the same way as we used it to explain the
existence of life here in the first place. The evolution of life is a
completely different case from the origin of life because, to repeat,
the origin of life was (or could have been) a unique event which had to
happen only once. The adaptive fit of species to their separate
environments, on the other hand, is millionfold, and ongoing.

It
is clear that here on Earth we are dealing with a generalized
process
for optimizing biological species, a process that works all
over
the planet, on all continents and islands, and at all times. We can
safely predict that, if we wait another ten million years, a whole new
set of species will be as well adapted to their ways of life as today's
species are to theirs. This is a recurrent, predictable, multiple
phenomenon, not a piece of statistical luck recognized with hindsight.
And, thanks to Darwin, we know how it is brought about: by natural
selection.

The
anthropic principle is impotent to explain the multifarious details of
living creatures. We really need Darwin's powerful crane to account for
the diversity of life on Earth, and especially the persuasive illusion
of design. The origin of life, by contrast, lies outside the reach of
that crane, because natural selection cannot proceed without it. Here
the anthropic principle comes into its own. We can deal with the unique
origin of life by postulating a very large number of planetary
opportunities. Once that initial stroke of luck has been granted - and
the anthropic principle most decisively grants it to us - natural
selection takes over: and natural selection is emphatically not a
matter of luck.

Nevertheless,
it may be that the origin of life is not the only major gap in the
evolutionary story that is bridged by sheer luck, anthropically
justified. For example, my colleague Mark Ridley in
Mendel's
Demon
(gratuitously and confusingly retitled
The
Cooperative Gene
by his American publishers) has suggested
that the origin of the eucaryotic cell (our kind of cell, with a
nucleus and various other complicated features such as mitochondria,
which are not present in bacteria) was an even more momentous,
difficult and statistically improbable step than the origin of life.
The origin of consciousness might be another major gap whose bridging
was of the same order of improbability. One-off events like this might
be explained by the anthropic principle, along the following lines.
There are billions of planets that have developed life at the level of
bacteria, but only a fraction of these life forms ever made it across
the gap to something like the eucaryotic cell. And of these, a yet
smaller fraction managed to cross the later Rubicon to consciousness.
If both of these are one-off events, we are not dealing with a
ubiquitous and all-pervading
process,
as we are
with ordinary, run-of-the-mill biological adaptation. The anthropic
principle states that, since we are alive, eucaryotic and conscious,
our planet has to be one
of the intensely rare planets that has bridged all three gaps.

Natural
selection works because it is a cumulative one-way street to
improvement. It needs some luck to get started, and the 'billions of
planets' anthropic principle grants it that luck. Maybe a few later
gaps in the evolutionary story also need major infusions of luck, with
anthropic justification. But whatever else we may say,
design
certainly does not work as an explanation for life, because
design is ultimately not cumulative and it therefore raises bigger
questions than it answers - it takes us straight back along the
Ultimate 747 infinite regress.

We
live on a planet that is friendly to our kind of life, and we have seen
two reasons why this is so. One is that life has evolved to flourish in
the conditions provided by the planet. This is because of natural
selection. The other reason is the anthropic one. There are billions of
planets in the universe, and, however small the minority of
evolution-friendly planets may be, our planet necessarily has to be one
of them. Now it is time to take the anthropic principle back to an
earlier stage, from biology back to cosmology.

We
live not only on a friendly planet but also in a friendly universe. It
follows from the fact of our existence that the laws of physics must be
friendly enough to allow life to arise. It is no accident that when we
look at the night sky we see stars, for stars are a necessary
prerequisite for the existence of most of the chemical elements, and
without chemistry there could be no life. Physicists have calculated
that, if the laws and constants of physics had been even slightly
different, the universe would have developed in such a way that life
would have been impossible. Different physicists put it in different
ways, but the conclusion is always much the same. Martin Rees, in
Just
Six Numbers,
lists six fundamental constants, which are
believed to hold all around the universe. Each of these six numbers is
finely tuned in the sense that, if it were slightly different, the
universe
would be comprehensively different and presumably unfriendly to life.*

* I
say 'presumably', partly because we don't know how different alien
forms of life might be, and partly because it is possible that we make
a mistake if we consider only the consequences of changing one constant
at a time. Could there be other
combinations
of
values of the six numbers which would turn out to be friendly to life,
in ways that we do not discover if we consider them only one at a time?
Nevertheless, I shall proceed, for simplicity, as though we really do
have a big problem to explain in the apparent fine-tuning of the
fundamental constants.