<"Darwin was shocked, because Thomson's figure for the age of the earth
eliminated the possibility that his theory of evolution could be correct.
There simply would not have been time for the geological processes on which
Darwin's theory was based to have occurred. If Thomson was right, the earth
must have been created with a ready-made geology. Archbishop Ussher's date
of 4004 BC could be right."
MY COMMENT: The Ussher part is ridiculous, and likewise the part about "a
ready-made geology," which is worthy of AD White for its tone. On the other
hand, Darwin was seriously concerned about this. See below.
<He then tells of Darwin's son George verifying Thomson's calculations, and
then tells how those calculations were underestimates because of incorrect
assumptions about how the Sun worked and because he was not aware that heat
was generated in the Earth via radioactivity. The overall picture he paints
is one in which Kelvin had scored what even Darwin perceived as a near
knockout blow against evolution, and that the theory was only saved by the
discovery of radioactivity.
Harvey wants to know:
<Is this characterization anywhere near the truth? Kelvin's age
gave about 100 Myr, a factor of 45 less than the current best number. But
was enough known about the "speed" of evolution in the late 19th century to
say that 100 Myr would not have been enough time for Darwin's postulated
evolution to have happened? Certainly the more time the better for Darwin,
and if Kelvin had come up with 100,000 years that would have been a huge
blow to Darwinism. But was 100 Myr really low enough to discourage Darwin
and temporarily turn scientific opinion against evolution?
ANSWER: Darwin certainly did envision an earth much older than 100MY, the
upper end of Kelvin's calcuations. But (yes) there was no way to get ages
that we would today call reliable, and the absence of knowledge of
radioactivity is a major factor here. Most of Darwin's contemporaries, even
his friends like Huxley, tried to find ways to make evolution go much faster
than Darwin thought it did. They appealed to mutationism, neo-Lamarkianism,
or both; even Darwin himself modified his own theory significantly in later
editions of the Origin. This whole episode is part of what Peter Bowlers
calls "The Eclipse of Darwinism" in his book of that name. I also recommend
"Lord Kelvin and the Age of the Earth," by Joe Burchfield.
OVERALL: Youngson uses mainly facts to draw an absurd conclusion.