SNOWBRAWLS - Snowball Earth - page 84

W HEN N ICK Christie-Blick, Martin's co-author on the cement paper, heard Paul and Dan's new argu-
ments, he immediately cried foul. Paul and Dan, he said, were simply shifting their goalposts. How
could he and his fellow critics test their theory if they kept changing what it said? Paul and Dan re-
sponded that they were naturally modifying a young theory, making it richer and fuller.
Who's right? Well, science works at its best when somebody puts forward a theory and everyone
else tries to pull it down. Sacrosanct scientific philosophy holds that no theory can ever be proved . A
theory can only be disproved , and the longer it survives the attacks against it, the more confidence you
can place in it— while never knowing for certain if it is right. Following the philosopher of science
Thomas Kuhn, many see science as a procession of revolutions, where a prevailing paradigm holds
sway in researchers' minds until it is finally disproved and a new one takes its place.
The trouble comes in this process of disproving. Scientists often—perhaps usually—find it hard
to let go of a theory that they care about. When some devastating new finding shows it to be wrong,
that's hard for them to accept. There are many theories whose proponents have clung on to them for
too long, rendering them more and more elaborate in a desperate attempt to accommodate the findings
that disprove them and ward off the inevitable end.
But science moves much more in fits and starts than a simple reading of Kuhn's paradigm shifts
would suggest. And it can be hard to decide whether a theory has truly been disproved. Often counter-
arguments can be incorporated into the theory itself until it becomes richer for having adapted and
allowed itself to grow. If a theory comes under attack when it's too young and raw to defend itself, it
can also be destroyed prematurely. Wegener's theory of continental drift is one example of this. And
Alvarez's asteroid hypothesis about the death of the dinosaurs could have encountered the same fate
if someone hadn't found the crater— the “smoking gun”. Even that was lucky. The crater could have
long since been swallowed back up into the Earth's interior, as much of the rest of the Earth's crust has
been since the time of the dinosaurs. Alvarez's theory might have been right, and yet could still have
been killed.
Though Martin's cement paper may not have tripped up the Snowball idea, as he had thought it
would, it had taught Paul one lesson at least: when under attack, try to spread out the target area. The
next time I saw Paul at the beginning of a new lecture tour, the Snowball had become “Kirschvink's
theory”. Every time he mentioned the idea, Paul was reminding his audience that it had come, in much
of its modern incarnation, from the insights of Joe Kirschvink, the Caltech professor who had dreamt
up the volcanic aftermath, and coined the name Snowball Earth.
Paul even described himself as “Kirschvink's bulldog”. That was neat, a direct reference to Tho-
mas Henry Huxley, who earned the nickname “Darwin's bulldog” for his blunt and ferocious defence
of Darwin's ideas on evolution. Darwin shrank from crusading against the disapproving Anglican es-
tablishment on behalf of his worrisome new theory. Huxley, however, had no such qualms. At a debate
in 1860, when Bishop Samuel Wilberforce asked sarcastically whether Huxley would prefer to be des-
cended from an ape on his grandfather's or grandmother's side, Huxley reportedly replied thus:
If the question is put to me, would I rather have a miserable ape for a grandfather, or a man
highly endowed by nature and possessed of great means and influence, and yet who em-
ploys these faculties and that influence for the mere purpose of introducing ridicule into a
grave scientific discussion, I unhesitatingly affirm my preference for the ape. 6
Meanwhile, Martin's paper on the cements had done something else for the Snowball idea. He had
finally focused attention back on to the question of what exactly was alive in the Snowball ocean. This
was something that was beginning to worry many biologists. They knew that certain creatures must