Geoscience Reference
In-Depth Information
are now known to be coeval or equivalent. In the Harlech Dome in
Wales the Cambrian Garth Hill Beds crop out, and these are correlated
with the uppermost Lonan and Niarbyl Flags of the Isle of Man.
Fortunately this problem was addressed by a commission established
by the International Geological Congress and it arranged for the pub-
lication of the Lexique Stratigraphique International, which provided
information on geological names used in nearly every country in the
world; this resource has proved to be of huge value to stratigraphers
attempting tricky intercountry correlations.
EVOLUTIONARY QUESTIONS AND THE PAUCITY OF TIME
It was inevitable that at some point in the past an interested scientist
would ask questions pertaining to the ancestry of fossil groups and the
sudden appearance and disappearance in the fossil record of certain
plants and animals. Geologists and biologists recognised that strata of
a particular age contained fossils of organisms that appeared to be no
longer extant. What had happened to them? Cuvier in 1801 had asked
this question and speculated that animals might have become extinct,
might have evolved into another species, or might have migrated to
another place. He favoured extinction. Early workers also realised that
some organisms appeared to have linkages, such as the animals with
backbones, the chordates. Here the first fishes were found in the oldest
successions and preceded the amphibians, which in turn were fol-
lowed by reptiles and finally the mammals which were confined to
the younger sediments. Were these groups interrelated, and if so, had
shared morphological characters been passed on? Could supposed
shared features appear independently in different groups? Is the fish
fin related in any way to a human humerus? Could one organism
metamorphose into another similar organism?
These questions, which we would now group into the realm of
evolution, were first tackled in the early 1800s. Jean Baptiste Pierre
Antoine de Monet de Lamarck (1744-1829) was a soldier until he was
wounded in 1726, which resulted in his being invalided out of the
French army. He then turned to the study of natural history and joined
