The Forbidden Universe (33 page)

In the last chapter we saw that advances in cosmological understanding point firmly in the direction of the design interpretation of the anthropic principle, suggesting that the universe was intentionally fine-tuned – by whom or what we have no way of knowing – specifically to make it suitable for intelligent life. But this only concerns the physics, the manufacture of the elements necessary for life and the planets where it can dig in and thrive. What about the next step? How are living things actually made? And do the processes that create life support the designer universe hypothesis?

After all, if life itself turns out to be an incredible fluke, the whole idea of a designer universe would be
undermined
. On the other hand, if the laws of physics have been rigged to produce a universe agog for life, we would expect the rules of biochemistry to be similarly primed to ensure life develops wherever and whenever it can.

Frustratingly, however, matters are not as cut and dried as they are with the physics, since there are enormous gaps in the available data. Charles Darwin wrote to his great friend, the botanist Joseph Dalton Hooker, in 1863, four years after the publication of
On the Origin of Species
, saying: ‘It is mere rubbish, thinking at present of the origin of life; one might as well think of the origin of matter.’
¹
Although
150 years later we know considerably more about the origin of matter itself, our information on the origin of life is still largely ‘rubbish’. Darwin’s foremost modern apostle, Richard Dawkins, writes in
The Greatest Show on Earth: The Evidence for Evolution
(2009) that ‘we have no
evidence
bearing upon the momentous event that was the start of evolution on this planet’.
²
‘
No
evidence …’ None whatsoever.

Since Darwin took the discussion of the evolution of life to a new level in the mid-nineteenth century, biologists’ growing understanding of the conditions necessary for complex life forms could be extrapolated in two
diametrically
opposite directions. Some still consider that the chain of events that led to life on Earth was so dependent on chance that organic life must be an extremely rare phenomenon, cosmically speaking. Some even argue that the odds are so stacked against the development of life that Earth may be unique in the universe. Yes, they claim, we are alone – get used to it. On the other hand, some believe the processes that produce life unfold according to rigid laws. What happened here will happen anywhere given approximately the same conditions. And given the vastness of the universe, even if those conditions were rarer than multiverses with life, there will still be millions of suitable locations for it to exist.

Once upon a time most biologists believed that life was an exceedingly rare phenomenon at best. But new discoveries in the last two or three decades prompted specialists to see it as a common, even inevitable, feature of the universe. A phrase that is often bandied around is that life is a ‘cosmic imperative’: the ordering of the universe means that wherever conditions are such that life
can
evolve, it
will
, just as weeds will seize on the tiniest nooks and crannies to grow and thrive. Life just can’t stop itself.

One of the foremost exponents of this school is Christian
de Duve, the Belgian biochemist and cytologist who won a Nobel Prize in 1974 for his work on cells. In 1995 he published
Vital Dust: Life as a Cosmic Imperative
, a detailed survey of the origin and development of life on Earth, from the first organic molecules to human beings. He writes:

It may be early days yet, and the evidence may be nowhere near as conclusive as that for the fine-tuning that led to the formulation of the anthropic principle, but the very fact that the study of the origins of life, or abiogenesis, is moving in this direction is implicitly designer-universe friendly. This also fits in with the Hermetic principle that the universe is teeming with life – or at least the potential for life. Giordano Bruno took this line of thinking to its logical conclusion, arguing for the existence of other inhabited worlds.

The modern trend towards seeing life as a cosmic inevitability arose largely from the growing recognition that the universe is brimming with the building blocks of life – not just on planets but even in deepest space.

The spring of 1953 was a big time for abiogenesis: two seminal scientific papers appeared within just three weeks, fuelling great excitement in the subject. The first was published in the 23 April edition of the British scientific journal
Nature
, by James D. Watson (a somewhat maverick American biologist) and Francis Crick (British
physicist-turned-biologist
), announcing their discovery of DNA’s
double helix. Then on 15 May the American
Science
carried a paper by Stanley L. Miller on his and Harold Urey’s re-creation at the University of Chicago of some of the fundamental chemical building blocks of life – most significantly certain amino acids – under simulated ‘primitive Earth’ conditions.

At the time, it was Miller who made the bigger splash. Watson and Crick’s paper was about what was then considered a very uninteresting nucleic acid, only hinting cautiously, in its very last sentence, that it might actually be the long-sought medium of genetic inheritance: ‘It has not escaped our notice that the specific pairing we have postulated immediately suggests a copying mechanism for the genetic material.’
⁴
But despite their laid-back comment, the discovery of DNA made the scientific landscape richer, more colourful and intoxicatingly alive with promise.

Miller’s paper, on the other hand, offered much more hope for unlocking the origins of life. It seemed to confirm the prevailing theory that it began in the Earth’s ‘primordial soup’ of biochemicals. The implication was that further research would reveal how the more complicated parts of the system came into being through similar processes – all of them essentially blind.

As we now know, by unravelling the genetic mystery, Watson and Crick’s discovery has had by far the greater impact, not just on science, but on our daily lives – witness, for example, the DNA ‘fingerprinting’ used to catch criminals. Urey and Miller haven’t fared nearly so well, partly because although their experiments showed amino acids and certain other biogenic chemicals could be produced easily in the lab, taking it further and putting the building blocks together in any more complex way remained out of reach. Since 1953 it has also been
discovered
that creating, for example, amino acids doesn’t require terrestrial conditions at all. Many of the building
blocks of life have been found literally floating around in space.

For a long time it was assumed that however life on Earth originated it happened
on
Earth. Even over a century ago this was not without its challengers, however. Great names of the Victorian age such as German physicist Hermann von Helmholtz and British physicist and engineer Lord Kelvin advocated that the seeds of life could be carried between planets by meteors and comets, a theory that was termed ‘panspermia’ in 1907 by the Nobel-prizewinning Swedish chemist Svante Arrhenius. He actually took the term from Athanasius Kircher who wrote of
panspermia rerum
, ‘the universal seed of things’. In turn, he had developed the concept from Bruno’s
spermia rerum
, meaning the basic unit of which everything is made – essentially atoms.
⁵

Panspermia’s most (in)famous recent champions were Sir Fred Hoyle and his long-time collaborator Chandra Wickramasinghe. With a typically robust side-swipe at his peers, Hoyle likened their view that life originated
exclusively
on Earth to the geocentric ideas that prevailed before Copernicus.
⁶
In a way he was right, their ideas effectively make our planet the
biological
centre of the universe.

And the increasingly exciting discoveries of the comparatively new field of astrobiology – developed in the late 1950s – reveal that there is no doubt whatsoever that many of the building blocks of life do have an
extraterrestrial
origin. The only real controversy is how far they were assembled before they arrived on Earth.

Certainly the chemical ingredients for life exist in space. Even the most remote regions of interstellar space are pervaded with gas and a much, much smaller amount of solid material in the form of extremely fine-grained ‘dust’. These cosmic grains are enormously significant. Until the beginning of the 1960s the consensus was that they were simply frozen clumps of gas molecules, but improved
technology has revealed that some were too close to stars to be frozen. So what could they be?

Enter the ever-energetic Hoyle and his newly arrived research student from Sri Lanka, Chandra Wickramasinghe. Their time working at Newton’s alma mater Trinity College, Cambridge marked the beginning of one of the most enduring scientific collaborations, one that continued after Wickramasinghe’s own glittering scientific career took off and only ended with Hoyle’s death in 2001.

It was Wickramasinghe who developed the idea that organic carbon-based chemicals form the major components of cosmic dust. When he and Hoyle first proposed this in 1962 it was, unsurprisingly, highly controversial. But research in the 1960s and 1970s vindicated it, and these days it is simply a given.

Formaldehyde, one of the simplest organic compounds, was detected in interstellar clouds in 1969, and since then a whole host of organic chemicals has been added to the list. By the end of the next decade over thirty complex molecules had been found in interstellar dust, including water vapour, carbon monoxide and ammonia. Organic molecules including methane, acids, alcohols and sugars have now been found. Even molecules of vinegar have been detected in a gas cloud in Sagittarius. Around 20 per cent of interstellar dust is now thought to be made up of organic chemicals. The discovery of so many prompted Hoyle and Wickramasinghe to propose, in the mid-1970s, that even more complex organic molecules could be lurking in the interstellar clouds, and that this was a better candidate for the origin of life than the terrestrial ‘primordial soup’.

One of the most significant discoveries in this field came in 2005 from a NASA team from the Ames Research Center in California, using data from the Spitzer Space Telescope. The team was studying a type of complex organic molecule with the uncatchy name of polycyclic aromatic hydrocarbons
(PAHs), a very common family of chemicals which, in the words of the team’s leader Douglas Hudgins, are found ‘in every nook and cranny’ of the universe. The fact that PAHs are abundant in space had been known for a long time, and few thought they were worth much of a second look. But the NASA team discovered to their great
astonishment
that the PAHs they were looking at – in a distant galaxy designated M81, 12 million light years away – were rich in nitrogen. This is considerably more significant than it might appear.

Without nitrogen PAHs tend to be hostile to the
biochemistry
of life. On Earth they are largely the result of the breakdown of organic material, for example the burning of fossil fuels, making them pollutants and in some cases carcinogenic. But with nitrogen it’s a different story. Without nitrogen-containing PAHs, amino acids, DNA and RNA, as well as a host of other vital molecules (for example haemoglobin, chlorophyll – and even essentials such as chocolate) could not exist. Indeed, one of the theories of how life originated on Earth puts nitrogen-rich PAHs right at the centre. But the big question is how they developed in the first place.

The discovery that nitrogen-bearing PAHs are present in space provides a major piece of the puzzle. The current understanding, based on the NASA Ames team’s work, is that they are formed and ejected into space by the death of stars. As Douglas Hudgins puts it:

Hudgins points out that discovering nitrogen-containing PAHs in interstellar space does not prove that life on Earth came from the stars but that as it is the simplest theory, according to Occam’s Razor, this is the one that science should prefer.

Another way that building blocks can be seeded on planets is via comets. Not through scoring a direct hit on Earth – which would incinerate any ‘seeds’ – but by drifting down with the ‘rain’ that floats into the atmosphere as the planet passes through the debris from the tail of comets.

Most comets are believed to be left over material from the gas and dust clouds that coalesced at the birth of the solar system, now roaming its highways and byways under the influence of the gravity of the heavenly bodies, generally orbiting the sun. The endless process of heating and freezing as the comet approaches and recedes from the sun causes reactions in its basic chemicals, which creates new compounds.