He was refering to natural selection only. here is the beginning of the
text thanks to brian for the whole quote):
Thanks for showing that SJ's interpretation of Popper is not supported by Popper's own comments.
"When speaking here of Darwinism, I shall speak always of
today's theory--that is Darwin's own theory of natural
selection supported by the Mendelian theory of heredity,
by the theory of the mutation and recombination of genes
in a gene pool, and the decoded genetic code. This is an
immensely impressive and powerful theory. The claim that
it completely explains evolution is of course a bold claim,
and very far from being established. All scientific theories
are conjectures, even those that have successfully passed
many and varied tests. The Mendelian underpinning of
modern Darwinism has been well tested, and so has the theory
of evolution which says that all terrestrial life has evolved
from a few primitive unicellular organisms, possibly even
from one single organism."
About natural selection he admits:
"I have in the past
described the theory as "almost tautological", and I have tried
to explain how the theory of natural selection could be untestable
(as is a tautology) and yet of great scientific interest"
But he explains in this paper that he had changed his mind on the
untestability of natural selection:
"Darwin's own most important contribution to the
theory of evolution, his theory of natural selection, is
difficult to test. There are some tests, even some
experimental tests; and in some cases, such as the famous
phenomenon known as "industrial melanism", we can observe
natural selection happening under our very eyes, as it were.
Nevertheless, really severe tests of the theory of natural
selection are hard to come by, much more so than tests of
otherwise comparable theories in physics or chemistry. "
Since Popper clearly says that there are available tests for this theory
(natural selection), showing that this theory is indeed testable, I
don't see how Stephen can interpret the whole paper the way he does.
Desperation?