Have you ever wondered why biologists don't consider this to be an argument against evolution at all?
They do. Why you think they don’t, it’s a mystery that was never resolved.
The Cambrian explosion is known among scientists as “Darwin's dilemma”. It’s a dilemma that Darwin acknowledged as a problem that defies explanation, simply because it disproves gradualism. As Stephen Jay Gould put it: “Nothing distressed Darwin more than the Cambrian explosion.”
In a moment of geological time, enormous diversification/radiation of life appeared in the exquisitely preserved fossils of the Cambrian period without any evolutionary history.
The geologically sudden appearance of all major complex animal phyla during this period without any trace of the gradual transitional steps is a mystery that was never resolved. Within the vast bulk of the Precambrian (about 3.5 billion years), there were no animals or any transitional steps to explain the Cambrian life. The development of these new animal types required a
massive increase in genetic information. “The big question that the Cambrian Explosion poses is where does all that new information come from?
Stephen J. Gould, acknowledged this problem. He said, “The Cambrian explosion was the most remarkable and puzzling event in the history of life”. He also said,
“The absence of fossil evidence for intermediary stages between major transitions in organic design, indeed our inability, even in our imagination, to construct functional intermediates in many cases, has been a persistent and nagging problem for gradualistic accounts of evolution”
2013, Dr. Mark McMenamin said, “It is hard for us paleontologists, steeped as we are in a tradition of Darwinian analysis, to admit that
neo-Darwinian explanations for the Cambrian explosion have failed miserably. New data acquired in recent years, instead of solving Darwin’s dilemma, have rather made it worse.”
Not acknowledging the Cambrian dilemma is a stance based on ignorant bias or mere wishful thinking not the evidence of the real world.
Here are some considerations/challenges to the ToE/Gradualism posed by the Cambrian explosion:
a) One of the most popular explanations for the missing Precambrian fossils is that the Precambrian animals were too soft and too small to have been preserved. Evidence showed very fragile and soft microscopic remnants of Precambrian life preserved in lower strata, which poses the question “why the larger ancestral forms that supposedly evolved into the Cambrian animals couldn’t be preserved”. IOW, if you can pursue something that fragile, why couldn't you in the same strata of rock preserve the immediate ancestor of a hard-shell trilobite?
b) The organisms that we know today fall into one or another of those major body plans first appeared in the Cambrian explosion, which deepens the Cambrian mystery since the major differences were present right at the beginning, it’s not a gradually increasing curve of the number of phyla growing over time as speculated by the ToE.
c) Neo-Darwinism proposes that new proteins are constructed by the dual mechanisms of genetic mutations and natural selection as the genetic instructions for building proteins are copied, an occasional error can alter their contents, if these accidental revisions prove beneficial to survival, they are selected or preserved and passed on to future generations over eons of time, these small changes accumulate and new proteins cell types and even Cambrian carnivores gradually evolved into existence,
which proved to totally contradict the evidence of the Cambrian life.
The biological structure of a Cambrian trilobite was as complex and sophisticated as a modern crab, its organs included a brain, gut, heart and compound eyes, each organ was constructed from specific types of cells each cell type was made from dozens of specialized protein molecules and each protein was assembled from DNA genetic codes, now for the evolutionary process to transform a simple Precambrian organism like a sponge with four or five cell types into a Cambrian trilobite, that's a huge leap in complexity that requires a vast amount of new genetic information, where does that information come from that's the central challenge to the ToE imposed by the Cambrian explosion.
d) The odds among all the possible amino acid combinations that mutations would stumble upon a combination of a
single new short functioning three-dimensional protein molecule/chain is roughly 1 in 10 to the 74th power or one chance in a hundred trillion trillion trillion trillion trillion trillion. So, on the question of something like the Cambrian explosion, it’s not possible that unguided random mutations and natural selection can accomplish what needs to be accomplished to explain new numerous functional proteins of all forms of life that appeared within that period.
But the inability of random mutations to generate genes and proteins is only part of the problem since the Cambrian body plans demanded more than new DNA genetic information, the body plan does not reside at the DNA level, while DNA carries the instructions to manufacture proteins
it cannot alone assemble them into cell types or arrange cell types into new "tissues and organs" or "tissues and organs" into body plans, instead
the formation of body plans ultimately requires another level of information/instructions that direct the development of complex animals from fertilized eggs to control the division, alignment and migration of cells toward targeted areas into patterns that will form the tissues and organs through a process of cell specification and differentiation to perform particular roles to be an eye, heart, limb, etc.
The process to build different kinds of organisms depends on the instruction set through the flow of info of a magnitude beyond anything that we can conceive.
The cell machinery does not just read the genome. It imposes extensive patterns of marking and expression on the genome. Without purposeful interpretation of DNA towards meaningful functions, the DNA is nothing more than storage of coded info.
The higher-level information that's required for building new tissues and organs and body plans isn't found in DNA, that means that you can mutate DNA indefinitely without respect to probabilistic limits, without respect to time and number of trials and you're never going to get the kind of form and structure you need to build a new organism. The DNA is simply the wrong tool for the job and no amount of time is going to overcome that limitation. That has a devastating implication for the Neo-Darwinian mechanism of random mutation and natural selection because it also fails to explain the origin of the huge volume of complex information that controls the development of the body plans of the Cambrian life.