I have found a site that argues the fact that our concept of early earth may be slightly off.
It states that the levels of oxigen may have been higher than previously anticipated and that in fact may have been enough to sustain plant life, as
such that oxygen that was presumed to almost inexistant (two thousand five hundred million years ago) shows viable evidence of its presence. It also
states that the theory of a reducing or neutral atmosphere in early earth history in some instances lacks viable supporting evidence. by taking rock
sediment and measuring the amount of iron in trace water one can extrapulate the amount of oxygen present at its formation. The concept is that
"the lower the level of oxygen ions in water (and the greater the level of hydrogen ions), the more iron can go into solution. However, the rates of
dissolution have to be assessed experimentally. It is found that the reactions for Fe3+ compounds proceed very slowly. The prediction is that Fe2+
will be lost more readily than Fe3+. Using Titanium as a `standard' immobile element, the prediction is that a "reduced"-type (R- type) paleosol
will have significant reductions in the ratio Fe2+/Ti but little or no decrease in Fe3+/Ti. According to Ohmoto(resercher in mentioned page), none of
the paleosol sections examined yielded this characteristic. Thus, there are no paleosols that support the idea that the earth's early atmosphere was
reducing (or neutral, for the same reasons). "
If our measurments' available result in an erroniouse interpretation of available oxigen for the entirety of prehistoric history, then a
re-examination of our understanding of prehistroic life is called for. In fact the available oxygen for those lifeforms durring their existance is
greater than anticipated. showing a dramatic reduction up into our own times.
"minimum pressure of atmospheric oxygen consistent with the data is greater than 1.5% of Present Atmospheric Levels. for the entire period of 3.0 -
1.8 Ga. " (300,000 million years-100,000million years),contrary to the accepted notion of they're being that or far less.
If life forms that grew so large and vegetaion that grew so dense and large as well, had greater oxygen levels than we thought present as they
developed, it would be an obviouse reason as to why their size changed as these levels toped off to present day conditions. Imagine now the changes
humans have undergone as a result of this ruducing atmosphere.
It might be argued then that since there is a definite pattern to the reducion in size of reptiles, progresivley, as we look at history
chronologically, we could corelate it then to the progresively reducing oxygen in the atmosphere that eventually brings us to our present atmospheric
conditions. Bearing in mind that there was greater oxygen present at the start of this "count down", we may attribute the great size of things to a
oxygen rich environment. I think the problem is that previously we measured the earths atmosphere realtive to our own atmospheric conditions as being
"optimal" for sustaining life.
We lack any fossil record from that time of anything beyond single celled organisms.(3.0 - 1.8 Ga) It might be noted that that does not mean there was
no complex life. Just that we have no record of it. This means we do not know the average life spans of living creatures of that time..since we think
there were none. I argue now that if compared to life spans of living creatures are enjoying now, we might find a progressive change. Using
reptiles' almost unrestricted growth as an anchor and their presence on earth now in vastly reduced sizes, I see a direct link between environmental
conditions being more favorable to life in times past than now. If not there would be some form of large reptile in existance, comparable to