Darwin considered the Cambrian fossils to be a problem for evolution because of their sudden appearance of complexity rather than slow and gradual. One of which that could disprove evolution entirely. But it was widely believed that eventually answers would come with future science which is a common theme in various explanations of evolution. Well, with future science many more Cambrian fossils have been discovered!
And has it answered questions that plagued Darwin? No! There are attempted explanations of the data (like hyper-evolution) but the pattern of sudden appearance of complex remains. Animals that have complex digestive systems, eyes, and nervous systems. Precambrian fossils were thought to be the answer to the problem, but the ones discovered there so far have no relationships with animals.
In the Deadwood Formation where it was thought to have formed very slowly, a group of scientists from different countries had discovered exquisitely-preserved crustaceans which they said had a ” surprisingly modern aspect” in the mudstone!
PNAS described it this way…
“The early history of crustaceans is obscured by strong biases in fossil preservation, but a previously overlooked taphonomic mode yields important complementary insights. Here we describe diverse crustacean appendages of Middle and Late Cambrian age from shallow marine mudstones of the Deadwood Formation in western Canada. The fossils occur as flattened and fragmentary carbonaceous cuticles but provide a suite of phylogenetic and ecological data by virtue of their detailed preservation. In addition to an unprecedented range of complex, largely articulated filtering limbs, we identify at least four distinct types of mandible.”
“Together, these fossils provide the earliest evidence for crown-group branchiopods and total-group copepods and ostracods, extending the respective ranges of these clades back from the Devonian, Pennsylvanian, and Ordovician. Detailed similarities with living forms demonstrate the early origins and subsequent conservation of various complex food-handling adaptations, including a directional mandibular asymmetry that has persisted through half a billion years of evolution.”
“At the same time, the Deadwood fossils indicate profound secular changes in crustacean ecology in terms of body size and environmental distribution. The earliest radiation of crustaceans is largely cryptic in the fossil record, but “small carbonaceous fossils” reveal organisms of surprisingly modern aspect operating in an unfamiliar biosphere.”
There were other crustaceans that had been discovered in the Cambrian. Since the fossil record disagrees with the evolutionary timeline of slow and gradual, these scientists pushed back the timeline for example, branchiopods were pushed back 80-100 million years. With the problem of complexity so early in the fossil record, these scientist tried their best to explain differences between modern ones but nevertheless, “direct evidence for sophisticated particle-handling” and represent “the acme of Cambrian differentiation within appendages…”
In order to reconcile fossil copepods which are larger than modern ones. They suggested that there was a presence of fish with predatory eyes which drove the crustacean size down. But perhaps they overlooked something, fish fossils were discovered by the Chinese back in 2002-03, in the early Cambrian!
There biggest problem with these amazing fossils of animals is the fact that with all those complex body parts represented in an early part of the fossil record is how a gradual, unguided evolutionary process would lead to such complex levels of function in such a short period of time, abruptly, with no fossil pathway on how it got there, much earlier than expected.
In a more recent discovery, a new species of filter-feeding marine animal that resembles a tulip was discovered on Mt. Stephen in British Columbia.
Phys.org describes this way…
“Officially named Siphusauctum gregarium, fossils reveal a tulip-shaped creature that is about the length of a dinner knife (approximately 20 centimetres or eight inches) and has a unique filter feeding system.”
“Siphusauctum has a long stem, with a calyx – a bulbous cup-like structure – near the top which encloses an unusual filter feeding system and a gut. The animal is thought to have fed by filtering particles from water actively pumped into its calyx through small holes. The stem ends with a small disc which anchored the animal to the seafloor. Siphusauctum lived in large clusters, as indicated by slabs containing over 65 individual specimens.”
This amazing fully-formed animal, which includes a gut, foot anchor and pump to drive water through its complex and “unusual filter-feeding system” implies a very short time period between the Precambrian and its abrupt appearance.
This is why the Cambrian explosion has been and will continue to be quite amazing. Its data confirms creationism, while evolution the data continues to make predictions and expectations on what the explanation of evolution is supposed to do rather than the other way around which generally is common with “theories” in science.