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Laetoli footsteps

• three and a half million years (my) old hominid footprints in fresh volcanic ash (Laetoli, East Africa).
The volcanic eruption is an example of inorganic interference; the footprints of life interfering.
Is the fact that the hominids went straight north proof of mental interference? Migrating birds and butterflies can also orient themselves.
For more information on Laetoli, see Mac Gillavry 2004, p. 89 (bibliography).












































































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(website version 2.30 - august 2007)


interference (continued)

     1. continuity
     2. discontinuity



discontinuity

The photograph at the left shows the famous Laetoli footprints, left by a pair of early bipedal hominids on a fresh layer of volcanic ash.
The entire set of preserved footprints of these two extends much further than shown. Of great interest is the fact that this pair went straight towards the north.
There is also a trail of a small predator (near the top) and of two hipparions. They all survived the calamity, but are now extinct.
It would seem at first sight that what happened on top of this ash-layer, once it was there, would not be relevant to my discussion. Only the nature and extent of land-surface it blanketed, would be of relevance. If this layer is just one on top of a stack of such ash layers, one on top of the other, it might seem that there was continuity. The evidence, however, suggests that each time there were animals going around, animals that suddenly were deprived of their means of existence.
Each time there would be discontinuity, interference in the normal goings on of things.

large area interference
The situation of the Permian Coconino sandstone has been discussed before
in 4.1 groundwork - preview.
This band of sandstone stretches over an enormous area. At the time of its formation (and of the underlying Hermite shales) the sea withdrew and all marine life was replaced by a terrestrial community, migrated from far away.
When the sea came back, terrestrial life was in return replaced by marine plants and fauna, that had been developing in the global ocean around the American continent.
Each break in the continuity of life in the entire area was revolutionary.
As will be seen below, these changes are a foreshadowing of the still greater changes going to take place at the end of the Permian period.

global interference
That there need be no connection at all between a new sediment layer, with what went on before, is shown by the case of the sudden impact of the Yucatan asteroid. This event is completely unconnected with the past situation.
At Stevns Klint in Denmark, on the other side of the world, deposition of chalky limestone suddenly stops and almost an entire thriving community of calcareous testproducing algae (Coccoliths) and animals is wiped out.

The top of this chalk is overlain by a thin bed of shale, dated 65 my old, and named fiskeler by the Danes because it contains some fish remains.
Surprisingly soon the deposition of calcium carbonate in the form of massive limestone is resumed, but with a different community of calcareous-test producing organisms (see figure previous page). This is the beginning of the Tertiary, the Danian.

This change of marine fauna all over the world meant:
    • no more ammonites
    • no more rudistids (gigantic Mollusc shells)
    • no more relatively large micro-Foraminifera
       (Globotruncanas and Heterohelicidae) of the upper Cretaceous
    • no more dinosaurs on land.

Life is resumed with new forms, that now develop from the species that managed to survive this catastrophe.
Though the local impact of this break was enormous, it happened unnoticed by the rest of the universe. The same applies to the Shoemaker - Levy comet; when it fell in broken pieces on planet Jupiter, nothing noticeable happened on earth.

Permian extinction
An even more serious mass extinction occurred at the end of the Permian (250 my ago). Then 90% of marine species became extinct, 60% of reptile and amphibian families, 30% of insect species, and most land plants. 23
Opinions on the reasons for this differ.
In the Grand Canyon section we are then at the top of the Kaibab limestone. The sea withdrew again and this catastrophe was here not followed by renewed sedimentation. The Kaibab surface, then not far above sea level and peopled by the survivors of the calamity, may have looked quite similar to the surface now, 250 my later, raised to an altitude of 2.000 meters and peopled with a recent fauna of chipmunks, porcupines, mules, guides and tourists.

In those 250 million years much has happened: mammals appeared, dinosaurs, pterodactyls, bats and birds. And in the world of plants: palms, grasses and flowers.

Mass extinctions, sudden changes of the circulation of the ocean, reversions of the magnetism, etc., nowadays form the basis for the new geological event approach to the study of the geological calendar of earth.
They mark changes in the composition of oceanic communities, that before the event were in equilibrium.

In the universe at large similar events may have played a role: novas, super-novas, gamma ray bursts, etc., may also have interrupted the normal goings-on in the development of nearby star clusters.

On our planet a new source of interference, greatly disturbing the normal goings on, made its appearance in the form of life.

continued


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