More than half a billion years ago most of the major animal groups appeared abruptly in what is known as the Cambrian Explosion. It initiated virtually all the major designs of multicellular life with barely a trace of evolutionary history. In a geological moment, the fossil species went from small worm-like creatures and the like to a tremendous diversity of complex life forms.

Evolutionists have had little success explaining this onetime event. Thomas H. Huxley likened it to a barrel that is filled rapidly with apples. Then it takes longer to fill the remaining spaces with pebbles, sand and finally water. Today’s explanations are more technical-sounding but no less reliant on speculation as opposed to direct description. Steven Stanley compared it to the introduction of bacteria croppers which prey on dominant species which previously had suppressed diversity. J. J. Sepkoski compared it to rapid growth of bacterial populations in a virgin petry dish. Were the Precambrian oceans a virgin ecosystem with the raw materials of oxygen and food supplied by ancient bacteria? Steve Jones wondered if the Cambrian explosion reflects some crucial change in DNA—life’s genetic material. "Might a great burst of genetic creativity," asks Jones, "have driven a Cambrian Genesis and given birth to the modern world?"

Now, thanks to new research, we have yet another explanation: calcium. Evolutionists are now saying that a rise in ocean calcium levels may have triggered the assembly of unicellular organisms into multicellular organisms and the rest, as evolutionists say, is history. As one report explained:

the question of what was the trigger for the single cell microorganisms to assemble and organize into multicellular organisms has remained unanswered until now.

What is astonishing is that there is anyone left out there who questions evolution. Can't they see that these guys are doing the heavy lifting? This is just rock solid investigative research, the kind we've come to expect from evolutionists.

Evolutionist Richard Lenski explains that evolution is both a fact and a theory. Lenski's reasoning is typical of evolutionary thinking and therefore useful in understanding this genre of thought. Lenski begins by defining evolution as biological change over time. Since such change is not controversial, it follows that evolution is a fact:

It is an incontrovertible fact that organisms have changed, or evolved, during the history of life on Earth.

Readers who first encounter such passages in the evolution literature may be surprised. Is this not a radical broadening of the very definition of evolution? How can mere change over time, which even the Genesis account calls for, be counted as evolution? This may seem to be a concession. Have evolutionists dropped the claim that strictly naturalistic explanations are sufficient to account for the origin of species?

No, evolutionists have made no such concession. It is typical to find in the evolution genre apparent logical disconnects such as this. In his article, Lenski explains evolution as the usual unguided biological variation coupled with natural selection (along with dozens of other occasional mechanisms, as needed).

So how should the reader understand and interpret the apparent disconnect. How can Lenski define evolution as mere change over time, but then swap back to the traditional understanding of evolution as strict naturalism? Is this an equivocation—a cheap ploy to prove evolution while bypassing its massive scientific problems?

No, this is not an equivocation. To understand the evolution genre one must understand the history of thought behind it. Even evolutionists are often not completely aware of this history, but the equating of evolution with mere change over time is shorthand for a centuries old metaphysical claim that underwrites evolution. The claim is that if God created the species they would be fixed. Indeed, divine creation would produce a static, unchanging world.

This thinking is often associated with the great eighteenth century Swedish botanist Carl Von Linne, or Linnaeus. At one time he advocated the fixity of species concept and later was troubled when he discovered hybrids—species that are produced by the crossing of two related species.

Linnaeus softened his doctrine of fixity of species, but this was inconsequential. His system with its conception of species became deeply rooted, and the nineteenth century began with the notion of species as immutable still strongly in place. This notion was increasingly being challenged but it was nonetheless a major obstacle for Darwin to overcome.

It was therefore highly significant when Darwin became persuaded that related populations of birds he saw at the Galapagos were actually different species. If there was the slightest foundation for this idea, Darwin had anticipated in a famous notebook entry, it "would undermine the stability of species."

Today's readers often fail to understand the significance. After all, what can be so important about some different birds on some islands? Certainly the birds did not suddenly reveal to Darwin how fishes could change to amphibians, or how amphibians could change to reptiles, or how reptiles could change to mammals. Rather, the revelation was that the idea of divine creation was suddenly becoming untenable. The crucible for Darwin was not an abundance of positive evidence for evolution but rather negative evidence against creation.

Evolutionist Ernst Mayr has pointed out that Darwin's conversion from creationist to materialist was due to three key scientific findings and later reinforced by several additional findings. These scientific findings were all findings against creation. In other words, the key evidence that swayed Darwin was not direct evidence for evolution but rather evidence against creation that indirectly argued for evolution.

And as Mayr further points out, the doctrine of fixity of species was a key barrier to overcome in order if the concept of evolution was to flourish:

Darwin called his great work On the Origin of Species, for he was fully conscious of the fact that the change from one species into another was the most fundamental problem of evolution. The fixed, essentialistic species was the fortress to be stormed and destroyed; once this had been accomplished, evolutionary thinking rushed through the breach like a flood through a break in a dike.

The pre-Darwinian metaphysic was that species were fixed and essentialistic. Evidence for small-scale change argued against the old view and in so doing became an important proof text for evolution.

This is the story between the lines when evolutionists casually associate their theory with change over time. It is shorthand for a long-held tradition in the history of thought. If there is change, then divine creation is false, and if creation is false then evolution, in one form or another, is true.

Metaphysical claims such as these mandate evolution. They underwrite the fact of evolution. The rest is just research problems on how evolution occurred—the theory of evolution. As Lenski explains, evolution is both fact and theory. Religion drives science, and it matters.