Species Diversification Still an Evolutionary Puzzle
A look at another failed attempt
by evolutionists to explain
the origin of species
by Jerry Bergman, PhD
One of the main difficulties evolution encounters is explaining how species diversify. Ironically, that was the very question Darwin’s theory tried to explain: the origin of species by natural means.
For six thousand years, Bible believers have explained species diversity by creation as outlined in Genesis. God created all life kinds on Earth, they say, including the diversity of marine life, terrestrial life and atmospheric life. Each kind of life formed for life in the water, land, or air was created to reproduce after its kind. Bible believers do not teach fixity of species, but allow for variation within created kinds.
Environmental Speciation
A paper in Nature Ecology & Evolution by Laura A. van Holstein and Robert A. Foley on April 17, reviewed below, highlights the difficulties evolutionists face trying to explain species diversification within a Darwinian framework. Evolutionists limit themselves to explanations involving environmental influences.[1] Van Holstein and Foley attempt to answer the question, “What environmental factors explain species diversity?” First, they review theories for the origin of diversity of humans. These include:
Wolpoff’s ‘single species hypothesis’ which suggested that there can be no speciation in the hominin lineage, as its niche is ‘culture’. Culture, in Wolpoff’s view, is uniquely human and prevents boundaries between populations from occurring; hence, speciation was prohibited in hominins, but not in other clades.[2]
Wolpoff’s hypothesis sought to explain why only one species of humans exists (which, of course, is what the book of Genesis presents). Wolpoff’s theory implies that, because only one species exists, no inferior or superior races exist, because culture spreads throughout the hominin population. His view was very successful in addressing a major embarrassment in evolutionary theory: its use to promote racism—the most extreme example being the racism promoted by the Nazis which Hitler supported by appeals to the survival of the fittest.[3]
Other theories of speciation include
interpretations that emphasize commonalities between patterns of hominin speciation and extinction and those of other clades. Within this group, research interest has primarily been devoted to examining the role of climate in shaping hominin diversification.[4]
Climate has been useful to invoke as a politically-convenient causal force these days for explaining many things in evolution.
Competition-Based Speciation
The approach that species diversity is caused by climate, however, is obviously very limited in explaining the enormous numbers of species existing today. Therefore, van Holstein and Foley propose another hypothesis that they claim has, unfortunately, “received far less attention as a potential driver of hominin diversification than climate.”[5] This theory is that competition drives the exploration of ecological opportunities, leading to variability and speciation.
They argue that “Competition has probably had a major role in animal diversification … leaving signals in correlations between species diversity, on the one hand, and speciation and extinction on the other.”[6, italics added]. ‘Competition, also known as Positive Diversity’ is defined as speciation that is
a function of the novel evolutionary opportunities and interactions created by other species. This pattern is exceptionally rare among all life forms, having been reported only in island-dwelling beetles, plants and arthropods, and this latter case is contentious.[7]
Positive Diversity Examined
Positive diversity focuses on species formation that fills ecological niches. A primary illustration involves Darwin’s finches. In this longstanding, well-publicized example of environmental speciation, Darwinians point out that some finches developed large beaks to facilitate nut-cracking to obtain the nutrients inside of the nut, while other finches evolved small beaks to facilitate feeding on insects.[8]
Many problems face this approach to explaining species diversity. The finch-beak story gets repeated scores of times in the scientific literature because, as van Holstein and Foley admit, it is an iconic example. But, on the other hand, they admit that it is “exceptionally rare” to find illustrations like this in nature. One study from 2010 agreed, stating that
‘Darwin’s finches’ are a poster example of adaptive radiation…. most lineages that arrived at the islands did not radiate…. The ecological diversity of the Galápagos in part explains that radiation, but the fact is that other founder species did not radiate.[9]
This statement suggests that the finch example is abnormal, not really useful as an evolutionary icon.
Darwin’s finches. Note the beak differences and how tiny they are. From Wiki Commons.
Peter and Rosemary Grant, a husband and wife team, have studied Galápagos finch populations every year since 1976. What they found was not evidence of speciation due to Darwinian selection, but only changes in ratios of finch varieties. Darwin’s finches are part of the finch-sparrow supergroup of approximately 1,000 species. The 13 Galápagos finch species have different beak designs adapted to different diets. The Grant team observed that when the weather changed in Galápagos, the ratio of large-to-small beaks adjusted. When the weather reverted to previous conditions, the ratio of large-to-small beaks also reverted to its previous state.
The Grants watched the ratios change during the 1977 season. In that dry year, small seeds were exceedingly rare but large seeds with thick husks were still widely available. Thus the finches with larger, stronger beaks that could break open the large seeds increased in number. In contrast, during the 1985 drought, smaller seeds were more abundant, giving birds with smaller beaks a competitive advantage, resulting in them surviving better, and their offspring had smaller beaks. Generations later the ratio went back to the original beak size ratio. This is not an example of evolution, but of the relative frequency of certain traits. When conditions changed to what they were before, frequencies went back to the previous levels.
Did Humans Diversify Through Competition?
The second step van Holstein and Foley took in support of the competition hypothesis was to use Bayesian modeling and phylogenetic analyses to see if most hominin species originated when competition for resources or space was low. They acknowledged that “the relationship between extinction and diversity has received less explicit empirical attention than” the positive diversity hypothesis, wherein species rise to fill new ecological niches, as was illustrated by the Darwin’s finches example discussed above.
Next, Van Holstein and Foley tested the diversity-dependent macroevolution hypothesis using a database of hominin fossils to infer origin and extinction evidence using birth-death models.
The main problem with their analysis was a dubious assumption. They assumed all of the fossils listed in their chart were uncontroversial. The fact is, they are all very controversial, as is well-documented in the extensive, peer-reviewed, paleontological literature.[10] Furthermore, van Holstein and Foley assumed that all of the 17 examples used were valid examples of separate pre-human species. They ignored the large well-documented literature challenging all of the examples that used, as documented in our book, Apes as Ancestors.[11] Their conclusions, therefore, are not trustworthy.
The pattern we see across many early hominins is similar to all other mammals. Speciation rates increase and then flatline, at which point extinction rates start to increase. This suggests that interspecies competition was a major evolutionary factor [that furthered speciation].
Wrong assumptions can lead to anomalies and surprises. For example, when van Holstein and Foley analyzed the presumed evolutionary trajectory of the genus Homo according to their hypothesis, their results looked ‘bizarre’. Specifically, for the Homo lineage (which includes modern humans), resulting evolutionary patterns contradicted their expectations. According to the model, competition between species resulted in the appearance of even more new species – a complete reversal of the trend seen in almost all other vertebrates.
The more species of Homo that existed, the higher the speciation rate. So when those niches got filled, something drove even more species to emerge. This is almost unparalleled in evolutionary science.[12]
Something was clearly wrong with the competition hypothesis, just like with the climate hypothesis. One important observation they made was that fossils can be an unreliable measure of species’ lifetimes: “The earliest fossil we find will not be the earliest members of a species.”[13]
Summary
What this new model reveals is that the issue Darwin spent much of his life working on—the origin of species—continues to evade an evolutionary solution after 160 years of research and hypothesizing. The van Holstein and Foley research discussed above only attempted to determine what environments are conducive to speciation, but they ignored internal genetic factors involved. The attempt to support one hypothesis (i.e., that species diversity arises through competition for ecological niches) produced results in the Homo lineage that were ‘bizarre’—the opposite of their expectations. One possible reason for this anomaly involved wrong assumptions about classification. They should have considered the possibility that some of these human or hominid fossils were varieties within the same species, or represented totally different lineages outside the human family, such as the great apes. Because of this oversight, their conclusions cannot be deemed any more reliable than any of the other failed explanations for the origin of species.
References
[1] van Holstein, L.A., and R.A. Foley. “Diversity-dependent speciation and extinction in hominins.” Nature Ecology & Evolution; https://doi.org/10.1038/s41559-024-02390-z, 17 April 2024.
[2] van Holstein and Foley, 2024.
[3] Cornwell, J. Hitler’s Scientists. Viking Press, New York, NY, 2003.
[4] van Holstein and Foley, 2024.
[5] van Holstein and Foley, 2024.
[6] van Holstein and Foley, 2024.
[7] van Holstein and Foley, 2024.
[8] van Holstein and Foley, 2024.
[9] Tebbich, S., et al. “The tale of the finch: Adaptive radiation and behavioral flexibility.” Philosophical Transactions of the Royal Society of London B: Biology Science 365(1543):1099–1109, 12 April 2010.
[10] Bergman, J., P. Line, and J. Tomkins. Apes as Ancestors: Examining the Claims About Human Evolution. Bartlett Publishing, Tulsa, OK, 2021.
[11] Bergman et al., 2021.
[12] van Holstein and Foley, 2024; emphasis added.
[13] Lewsey, F. “Competition between species played a major role in the rise and fall of hominins, and produced a “bizarre” evolutionary pattern for the Homo lineage.” https://www.cam.ac.uk/research/news/interspecies-competition-led-to-even-more-forms-of-ancient-human-defying-evolutionary-trends-in.
Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,900 publications in 14 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.