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The so-called “hard parts” first appeared in rocks deposited during the “Cambrian explosion,” around 530 million years ago. These 'hard parts', like shells and bones, are found in most metazoan organisms, but not all - like sponges.
"The seemingly sudden appearance of diverse, complex animals, many with hard parts, implies that there was a preceding interval during which early soft-bodied animals with no hard parts evolved from simpler animals. Unfortunately, until now, possible evidence of fossil animals in the interval of “hidden” evolution has been very rare and difficult to understand leaving the timing and nature of evolutionary events unclear"
Artist's' impression of Cambrian checking more realistic
Thanks to Humbold NHM Oregon
This conundrum, known as 'Darwin’s dilemma' (Morris, 2006) remains tantalizing and unresolved 160 years after the publication of 'On the Origin of Species'. Perhaps the soil can solve the puzzle. 0.5 Billion
Marine
Marine
The Cambrian Age explodes with marine life. Darwin had wondered where all that hard bodies life forms had come from. Since then, we have found loads of early life forms of unicellular and multicellar organisms going back 2 or 3 billion years previously.
It is all in the seas – trilobites - and in sands and silts lying there. The explosion was predominantly aquatic. There may have been silt but not soil. The Cambrian is unique in its unusually high proportion of lagerstätte sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells and other hard parts. As a result, our understanding of Cambrian biology surpasses that of some later periods.
Fungi
Fungi
Fungi became distinct from plants and animals around 1.5 billion years ago (Wang 1999). The 'glomaleans' branchied from the "higher fungi" (Dikaryans) (Hibbett 2007) at around 570 mya according to DNA analysis. (Schüssler et al., 2001). Fungi probably colonized the land during this Cambrain period (Taylor & Osborn, 1996), and possibly 635 million years ago during the Ediacaran period. We shall see how their presence influenced soil development in the Devonian period, later
Biofilms full of bacteria were spreading across the plains, where lichens and fungi were starting to grow.
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