Evolution is a word that refers to many different processes (chemical evolution, microevolution, microbial evolution, speciation, and macroevolution) with different underlying mechanisms. And as with any word with multiple meanings, one has to be careful not to equivocate when speaking about evolution—so I periodically speak on the topic of “Unequivocating Evolution” at various RTB events.
Species is another word that has multiple referents, and it too is frequently equivocated during discussions of evolution. The ambiguous and confusing nature of the term species actually has a recognized name—it’s referred to as the “species problem.”
The Species Problem
The species problem results from the wide range of approaches that can define how species are identified and how species function in nature. Each approach is known as a “species concept.” The number and types of species concepts that exist are constantly changing, but there are at least 26 recognized species concepts today.
That’s phenomenal! So when we’re talking about evolution and speciation, we have to ask, What do we mean by species? Unless we can clarify that, we can’t communicate. We know speciesrefers to a taxonomic level—species, genus, family, order, class, phylum, kingdom—but we don’t always mean the taxonomic definition when we use the word species. What the word speciesindicates is dependent upon which type of organism we’re talking about. When we talk about speciation, it’s critical that we realize the equivocation around the word species.
Speciation refers to adaptive changes in multicellular organisms that reproduce sexually. It refers to the process in which a given species becomes a genetically, phenotypically, and behaviorally distinct species, typically due to geographical isolation and resulting in reproductively independent populations.
During speciation, radiation events occur when a single starting species is split into various ecological niches where they encounter variable environmental pressures. In relative isolation, the organisms undergo different types of environmental stresses and pressures that affect the organism at a microevolutionary level and also at a genetic-drift level. These variable stresses and environmental pressures can also result in epigenetic changes that can affect a species’ phenotype and behavior.
Over time, each niche will mold and support a species that will be genetically, phenotypically, and behaviorally distinct from the starting species and from one another. These groups reproduce within themselves as a new population. And they may become so distinct genetically, phenotypically, and/or behaviorally that they no longer reproduce cross-species—either going back to the originating species or with the other species that are radiating from the same event. A recent article in Science highlights one aspect of the species problem.1
Rethinking the North American Wolf
Recently, genomic analyses indicate that North American wolves seem to be hybrids of various canids. Red and eastern wolves are geographically, phenotypically, and behaviorally distinct canids protected as endangered species in the United States and Canada. But recent genomic studies indicate that these “different” species are genetic hybrids of coyotes and grey wolves. The new data threatens their protected classification and status and highlights the species problem in regard to evolution.
Much like selective breeding resulting in a wide range of dog breeds, wolves, coyotes, and dogs seem to be the result of variations over time within an ongoing species-radiation event. No doubt populations are isolated now due to phenotypic and behavioral changes, as well as geographic localization. But there is no indication that the various “species” are genetically isolated from crossbreeding.
Another study late last year claimed the evolution of three new wasp species.2 But careful reading of the actual journal publication indicates that this could be a species problem as well as another example of equivocation of both the words evolution and species.3
Coadaptation of Wasps, Flies, and Plants
Speciation events can actually occur in ecologically linked coadapting species. In November 2015, a report touted the evolution of three new species of wasps.4 However, the referenced publication didn’t show that at all. If you actually read what was reported, what you would see is that there was a change in plants that affected flies that fed on the plants—which, in turn, affected wasps that fed on the flies.
Environmental changes triggered changes to the existing plants in a given ecological niche. As a result, the change in plants led to a change in feeding behaviors of various flies. The changes in the behaviors of the flies, in turn, led to changes in the behaviors of wasps, which fed on the flies. The wasps had significant behavioral changes, some phenotypic changes, and some genetic changes. But the researchers started with three species of wasps and ended with three species of wasps that were, to a certain extent, genetically, phenotypically, and behaviorally altered. The researchers did not examine whether the wasps were reproductively isolated following these changes.
This research shows a connection of species within an ecological web, where various species coadapt when driven by environmental changes. But it has no significance for macroevolution, the changing of a particular species to an utterly different taxonomical classification. And as the North American canid study shows, even if you called the new species something entirely different (e.g., wolf, coyote, or dog), it does not mean that one kind (canid—a derivative of their family-level classification, Canidae) has given rise to anything other than a varietal of canid. Darwin’s finches were all finches. Stephen J. Gould’s snails—all snails. Wasps and flies still remain wasps and flies.
Homo sapiens sapiens
Finally, consider speciation in the context of what we believe as Christians—that there was a primordial human pair, Adam and Eve, created in the image of God. In his image he created them, male and female. And if you believe the scientific data that traces mitochondrial Eve to roughly 150,000 years ago and Y-chromosomal Adam to about the same time frame (plus or minus the range of error), then you believe that God created man and woman as a primordial pair. Yet if you look around today, you see immense diversity in the human population. Consider the differences of the major races and ethnicities. Compare some of the Australian island groups to Asian, Middle Eastern, European, or Native American peoples. Consider dwarfs or extremely tall people. Regardless of our extreme diversity, we are all human. We are all Homo sapiens sapiens.
I, for one, rejoice in the diversity of God’s creation—even the diversity within various species! The rich capacity for diversification and adaptation built into all living things so we might thrive under various environmental stresses gives me added impetus for praising our great Creator.