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Evolution and the Fossil Record
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 A convincing argument for evolution can be made
from the fossilized, extinct life forms found in rock formations, whose
age can be determined. Darwin likened these remains to the dropped, decayed
branches of the great tree of life, which fill the crust of the earth;
these are whole families and genera of which there are now no living representatives.
Meanwhile, the living branches and twigs, or species, continue to branch
out and cover the earth with ever greater ramifications. Although there
were competing theories of evolution in the 19th century, the most successful
of these was launched with the 1859 publication of Charles Darwin's On
the Origin of Species by Means of Natural Selection, or the Preservation
of Favoured Races in the Struggle for Life (the title says it all). Darwin (1809-1882) developed many of his ideas for Origin of Species from observations on a five-year voyage of scientific exploration on the
H.M.S. Beagle. The British stamps above hint at quirks of evolution of
the exotic fauna he encountered in the Galapagos Islands, where isolation
from the mainland and other continents brought forth specialized beaks
in finches, among other developments. |
 Eohippus, a primitive four-toed horse of Europe
and North America, is the oldest fossil record of the evolution of the
horse family. This dog-sized animal dates back to the lower Eocene period,
or 50 million years ago. The German stamp shows a German fossil; the U.S.
stamp, an artist's conception of the animal that roamed this country.
The companion stamp to the little horse shows a fossil bat. |
 Archaeopteryx (above, bottom row, center), the most
ancient type of fossil bird yet discovered, dates from the upper Jurassic
period, or 160 million years ago. The fossil has a reptilian skull and
tail, somewhat like those of the pterodactyl shown at right in the row
above. The ubiquitous trilobite appears on many stamps; it is a common,
small, and easily recognized fossil. |
 Prehistoric life in Canada is depicted on this block: trilobite (Cambrian) sea scorpion (Silurian) fossil algae (Precambrian) soft invertebrate (Cambrian) |
 Dinosaurs have been extinct for the last 60-odd
million years, but they are now all the rage in movies, books, toys, and
also on stamps, as more and more fossils are uncovered. Many countries
have issued stamps featuring skeletons, or startling "true-to-life" artists'
renditions to satisfy the popular interest. These Lesotho stamps retain
some of the mystery surrounding these large beasts and their sudden demise,
perhaps from a earth-meteor collision that caused catastrophic climatic
changes and plunged our world into temporary darkness. Plateosaurus was
a genus of moderate-sized chiefly bipedal Triassic (150 million years
ago) saurischian dinosaurs whose fossilized footprints can be found in
Lesotho, Africa. |
 While most of the fossils we encounter are of now extinct species, there is one which surprisingly turned up alive in the past century. Coelacanth fossils from about 360 million years predate the age of the dinosaurs, and this strange, primitive lobe-finned fish (fins that bring to mind the limbs of terrestrial animals) was thought to have become extinct with the giant reptiles about 80 million years ago. However, a specimen was caught in 1938 off the coast of South Africa and identified as a member of this genus, but it could not be completely preserved for further detailed study. Native fishermen in the area between the coast of East Africa and Madagascar, notably in the Comoro Islands, were alerted and delivered further catches of this rare fish which is virtually unchanged over millions of years. In 1998 a different species of coelacanths was discovered in Indonesia. These "living fossils" are thought to be the ancestors of terrestrial reptiles, or to share a common ancestor, such as the only other (now extinct) lobe-finned fishes, the Rhipidistia. When swimming, the fins of "old four-legs" do not move in unison as do the fins of a modern fish, but alternately, approximating the gait of quadrupeds (left front with right hind, right front with left hind leg). The South African stamp at left shows the rear view of this fish, being studied by a scientist in a small submarine. |
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