THE CONCEIT OF HINDSIGHT
History has been described as one damn thing after another. The remark can be seen as a warning against a pair of temptations but, duly warned, I shall cautiously ﬂirt with both. First, the historian is tempted to scour the past for patterns that repeat themselves; or at least, following Mark Twain, to seek reason and rhyme for everything. This appetite for pattern affronts those who insist that, as Mark Twain will also be found to have said, ‘History is usually a random, messy affair’, going nowhere and following no rules.
The second connected temptation is the vanity of the present: of seeing the past as aimed at our own time, as though the characters in history’s play had nothing better to do with their lives than foreshadow us.
Under names that need not trouble us, these are live issues in human history and they arise with greater force, and no greater agreement, on the longer timescale of evolution. Evolutionary history can be represented as one damn species after another. But many biologists will join me in ﬁnding this an impoverished view. Look at evolution that way and you miss most of what matters. Evolution rhymes, patterns recur. And this doesn’t just happen to be so. It is so for well-understood reasons: Darwinian reasons mostly, for biology, unlike human history or even physics, already has its grand unifying theory, accepted by all informed practitioners, though in varying versions and interpretations. In writing evolutionary history I do not shrink from seeking patterns and principles, but I try to be careful about it.
What of the second temptation, the conceit of hindsight, the idea that the past works to deliver our particular present? The late Stephen Jay Gould rightly pointed out that a dominant icon of evolution in popular mythology, a caricature almost as ubiquitous as lemmings jumping over cliffs (and that myth is false too), is a shambling ﬁle of simian ancestors, rising progressively in the wake of the erect, striding, majestic ﬁgure of Homo sapiens sapiens: man as evolution’s last word (and in this context it always is man rather than woman); man as what the whole enterprise is pointing towards; man as a magnet, drawing evolution from the past towards his eminence.
There is a physicist’s version which is less obviously vainglorious and which I should mention in passing. This is the ‘anthropic’ notion that the very laws of physics themselves, or the fundamental constants of the universe, are a carefully tuned put-up job, calculated to bring humanity eventually into existence. It is not necessarily founded on vanity. It doesn’t have to mean that the universe was deliberately made in order that we should exist. It need mean only that we are here, and we could not be in a universe that lacked the capability of producing us. As physicists have pointed out, it is no accident that we see stars in our sky, for stars are a necessary part of any universe capable of generating us. Again, this does not imply that stars exist in order to make us. It is just that without stars there would be no atoms heavier than lithium in the periodic table, and a chemistry of only three elements is too impoverished to support life. Seeing is the kind of activity that can go on only in the kind of universe where what you see is stars.
But there is a little more that needs to be said. Granted the trivial fact that our presence requires physical laws and constants capable of producing us, the existence of such potent ground rules may still seem tantalisingly improbable. Depending upon their assumptions, physicists may reckon that the set of possible universes vastly outnumbers that subset whose laws and constants allowed physics to mature, via stars into chemistry and via planets into biology. To some, this means that the laws and constants must have been deliberately premeditated from the start (although it bafﬂes me why anybody regards this as an explanation for anything, given that the problem so swiftly regresses to the larger one of explaining the existence of the equally ﬁne-tuned and improbable Premeditator).
Other physicists are less conﬁdent that the laws and constants were free to vary in the ﬁrst place. When I was little it was not obvious to me why ﬁve times eight had to give the same result as eight times ﬁve. I accepted it as one of those facts that grownups assert. Only later did I understand, perhaps through visualising rectangles, why such pairs of multiplications are not free to vary independently of one another. We understand that the circumference and the diameter of a circle are not independent, otherwise we might feel tempted to postullate a plethora of possible universes, each with a different value of. Perhaps, argue some physicists such as the Nobel Prize-winning theorist StevvenWeinberg, the fundamental constants oooof the universe, which at present we treat as independent of one another, will in some Grand Uniﬁed fullness of time be understood to have fewer degrees of freedom than we now imagine.
Maybe there is only one way for a universe to be. That would undermine the appearance of anthropic coincidence.
Other physicists, including Sir Martin Rees, the present Astronomer Royal, accept that there is a real coincidence in need of explanation, and explain it by postulating many actual universes existing in parallel, mutually incommunicado, each with its own set of laws and constants.* Obviously we, who ﬁnd ourselves reﬂecting upon such things, must be in one of those universes, however rare, whose laws and constants are capable of evolving us.
The theoretical physicist Lee Smolin added an ingenious Darwinian spin which reduces the apparent statistical improbability of our existence.
In Smolin’s model, universes give birth to daughter universes, which vary in their laws and constants. Daughter universes are born in black holes produced by a parent universe, and they inherit its laws and constants but with some possibility of small random change — ‘mutation’.
Those daughter universes that have what it takes to reproduce (last long enough to make black holes, for instance) are, of course, the universes that pass on their laws and constants to their daughters. Stars are precursors to black holes which, in the Smolin model, are the birth events. So universes that have what it takes to make stars are favoured in this cosmic Darwinism. The properties of a universe that furnish this gift to the future are the self-same properties that incidentally lead to the
* This ‘many universes’ idea is not to be confused (though it often is) with Hugh Everett’s ‘many worlds’ interpretation of quantum theory, brilliantly advocated by David Deutsch in The Fabric of Reality. The resemblance between the two theories is superﬁcial and meaningless. Both theories could be true, or neither, or one, or the other. They were proposed to answer completely different problems. In the Everett theory, the different universes don’t differ in their fundamental constants. But it is the entire point of the theory we are here considering that the different universes have different fundamental constants.
manufacture of large atoms, including vital carbon atoms. Not only do we live in a universe that is capable of producing life. Successive generations of universes progressively evolve to become increasingly the sort of universe that, as a by-product, is capable of producing life.
The logic of the Smolin theory is bound to appeal to a Darwinian, indeed to anyone of imagination, but as for the physics I am not qualiﬁed to judge. I cannot ﬁnd a physicist to...