An A–Zbound to survive more readily. What Darwinism adds to this
picture – and the thing that Popper thought of as its greatest
scientifi c achievement – is that the evolution of species will be
gradual; it will occur over long periods of time (though rates of
evolutionary change are typically far from clear).
Here are two striking things over which Darwinism struggles.
A fi rst is the origin of life. It is possible that at some point in the
future scientists who mimic what they take to be a primordial
soup in the laboratory will show that certain complex molecules
can take on some of the properties necessary for life, such as
replication. However, short of an amoeba springing out of the
test tube, this won’t prove life began this way, for life’s origins
seem lost behind the veil of deep time.
A second is the variety of life. This might be thought surpris-
ing. After all, is it not obvious that natural selection produces
an abundance of life, given time? Popper refutes this with a
thought experiment. Say life was discovered on Mars, but only
in the form of one type of primitive bacterium. Would people
say that Darwinism had been refuted? No: they would say
that only one bacterium was well enough adapted to survive.
So natural selection does not predict the variety of the species
we see on earth. Neither does it offer a particularly satisfactory
mechanism to explain it. All sorts of others are routinely pro-
posed. Further, there’s the issue of how separate species evolve,
as opposed to the variations within species. What is not clear is
how natural selection might lead to the discontinuities between
species – the moment when gene transmission stops – if species
themselves are the result of transmitted changes in organisms.
There are other questions. Take, for example, why what might
be called higher functions of living animals evolved – like con-
sciousness. Evolutionary psychologists will say that conscious-
ness evolved because it is adaptive; it has causal effi cacy in
the survival of the species concerned. But what this does not
explain is the experience of consciousness. Why did evolution
allow us not just to detect light that falls across the visible band-
width, but to see vivid colours, as colours, too?