Great Geologists | 51
Darwin’s explanation of the formation of coral atolls. Top figure: lower solid line, stage 1, a fringing reef (AB) abuts
the shoreline. Island sinks (because of subsidence) to upper dotted line, stage 2, barrier reef (A’) separated from
sinking island by lagoon (C). Bottom figure: lower solid line, stage 2 barrier reef (as for upper figure). Island sinks
further to upper dotted line, stage 3, an atoll (A’’), enlarged lagoon (C’) marks previous location of sunken island.
From The Structure and Distribution of Coral Reefs (1842).
returning home, Darwin started a new
notebook dedicated to capturing his
developing ideas on evolution, by 1842,
a ‘first-sketch’ of the natural selection
theory was complete.
An important development was
Darwin’s reading of Thomas Malthus’
work on population expansion, an
intellectual concern in the 19th Century.
In his autobiography, Darwin notes, “In
October 1838 … I happened to read for
amusement Malthus on Population, and
being well prepared to appreciate the
struggle for existence that everywhere
goes on from the long-continued
observation of the habits of animals
and plants, it at once struck me that
under these circumstances, favourable
variations would tend to be preserved
and unfavourable ones to be destroyed.
The result of this would be the formation
of new species”. This is the essence of
natural selection! In a given ecological
niche, competition to survive would
favour any characteristic that would
confer an advantage on offspring.
Over time, these characteristics would
increase, resulting in a form that was
distinctly different from its remote
ancestors.
Using his documentation from the
Beagle’s expedition, Darwin established
himself in scientific society in London
with the publication of Journal of
Researches (1839). In 1842, needing
peace and privacy in which to work and
suffering from progressively ill health,
Darwin and his wife Emma Wedgwood
(his first cousin) moved to Down House
in Kent. There, surrounded by a growing
family (ten children, seven of whom
survived to adulthood), he worked for just
two or three hours each day in isolation
from the normal cares of the world,
but in correspondence with scientists
from across the globe on a huge range
of topics. Despite this limited work
schedule, his output was immense.