| Why is
the Deep Past Important?
The
bones and stones of Inverloch offer us a window into the deep past, back
into the Mesozoic. Our remote ancestors, the mammals, then lived furtive
lives in the shadow of fearsome dinosaurs. To trace the origin and evolution
of mammals is important because it tells us about our own beginnings. It
tells us too, that life is uncertain because our Earth is an ancient, accident
prone rock suspended in the midst of immensity. But for the Alvarez
event that ended the Mesozoic Age in a cataclysm, the dinosaurs might
still rule the world. What of the human race and all its works then?
To study the evolution
of life on Earth is important too because Darwin's discovery of how the
multitude of living things came to be is the most profound revelation that
human thinking has experienced. Humankind has always felt a desire to answer
deep questions about this world, ever since there has been human culture.
We may treasure creation myths and fables as part of our cultural heritage.
But if we would learn the real truth about the history of our world, it
is to science that we turn.
Given the fact of evolution, might one
expect the fossils to document a slow, incremental change from ancestral
forms into descendants? This is not what the stones reveal. The discovery
of an unbroken chain of ancestors changing gradually into descendants is
a rare thing. Indeed the fossil book is a record of of discontinuities,
of seeming jumps (saltations) from one type of organism to
another, different type. Why is this so?
All his life Darwin held that the gaps
in the story of life on Earth are due to the unimaginable incompleteness
of the fossil book. Only the tiniest, tiniest fraction of all the
creatures that once lived and breathed are preserved in stone. The Earth's
surface is geologically dynamic : tectonic plates are subducted and dissolved,
strata are folded, compressed and metamorphosed, surface rocks are eroded
and obliterated. Only a tiny percent of fossil bearing rocks are exposed
at the surface anyway. Even the process of fossilisation is itself a rarity.
However,
against all odds, a very, very few, fossil lineages are surprisingly complete.
One such lineage is the succession of creatures that begins with therapsid
reptiles of the late Triassic and merges into the mammals of the Jurassic
and Cretaceous periods. Some members of the sequence are so intermediate
between mammals and reptiles it seems arbitrary where to draw the line
between mammal or reptile. These fossils indeed show us Evolution as it
happened. Questers are referred to Ridley's standard work (M. Ridley,
Evolution, 1993, Blackwell Scientific) for more info.
Science is like a gigantic jig saw puzzle
: each piece may be small but, piece by patient piece, the big picture
slowly reveals itself. For 10 years past the Inverloch dig has opened a
window into the evolution of mammals during the Mesozoic Era. It
puts Australian science on an international stage. It deserves to be supported.
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