On Darwin's Lost World - Part II

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So what do we (did Darwin) know by now (then) ?

• That living creatures from the very very ancient past (we're talking in terms of millions of years) were often found preserved in the rock record.
• That we could make out some things about the past environments from these fossils.
• Fossils showed specific associations: you saw only certain types and groups of fossils in certain suites of rocks (belonging to different periods of geological time).
• There came a dead end at the base of the Cambrian.

Scientists like to call this the Cambrian Explosion today, but back then, many of them were more inclined to dismiss this either as a figment of the imagination of relatively smaller body of researchers, or simply, incomplete/inaccurate science. That the Creator had made us all, was the popular view.

3 theories emerged to explain why we see the Cambrian Explosion (if it even is a real thing!):

Charles Lyell

Interestingly, it is said that Lyell wasn't entirely theologically happy with dismissing the idea of the Creator. Ironically, he did support uniformitarianism vs. catastrophism (simply put, you explain geological phenomena in terms of processes you still see today, rather than invoking incredible "special" events like the Noah's Ark). But thank God for his scientific and unbiased head. Lyell was a friend of Darwin, and when the world asked Darwin how he could be so sure there was an evolutionary root to all of us in this world when he couldn't see any evidence of it backwards from the Cambrian, Lyell came forth and said, because we haven't looked enough.

Back in the 19th century, Geology relied mostly on field observations. Marine expeditions were extremely rare, and technology was pretty basic. Lyell was smart to point out that possibly (probably) we hadn't found evidence, not because it wasn't there but simply...because we hadn't yet found it. One of Lyell's ideas was that the oceans could contain this evidence.

Reginald Daly

Brasier tells us that it all began with Abraham Werner. Werner was of the (incorrect) opinion that igneous rocks were precipitated out of evaporating oceans. But more interestingly, he also thought that pre-Cambrian oceans were a bad place for organisms to live in. It was Daly who resurrected this idea of a somewhat corrosive ocean, and tried to explain Darwin's quandary by saying that the environmental factors were trumping biological factors. The subtlety invoked was that the oceans simply did not have the necessary raw materials (in this case, calcium carbonate) for organisms to develop hard shells and thus be preserved.

William Sollas

Somewhat called Edgeworth David has mapped rocks down to pre-Cambrian levels. He was pretty sure there's enough calcium carbonate in the rocks to have warranted fossils. He also thought he saw a gradual thinning of shells when he went deeper in the rock record. Perhaps pre-Cambrian animals had existed, but simply did not have preservable parts.

(If you notice a hint of suspicion in my tone, it's because I'm not entirely sure if this thinning of shells is to be believed. There's a ton of literature about this already, I simply haven't found the time to peruse it. But I did not want to halt this post for lack of clarity on a certain nuance.)

Sollas picked up from David's ideas and proposed that the Cambrian Explosion was a result of the (evolutionary) event of organisms learning to build durable shells around themselves.

(On a side note, Wikipedia tells me that Sollas died on the 20th of October, which might not have qualified as my birthday back in 1936, but does still deeply grieve me. He died in office. Double blow.)

..to be continued.

Psst...like such posts?

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