What is Sympatric speciation?
National Geographic says, “Speciation is how a new kind of plant or animal species is created. Speciation occurs when a group within a species separates from other members of its species and develops its own unique characteristics.” Sympatric speciation is the “development of many similar species in a single habitat, each with a different specialization.” [1]
A) What is a Species?
The term “species” is tough to define. Evolutionary biologists mostly use the “biological species concept,” according to which species are groups of interbreeding natural populations that are isolated from reproducing with other such groups, i.e. when two creatures can breed and produce offspring, they are of the same species, but also of the same kind of animal.
B) Darwin and Incipient Species
Darwin used the term incipient species to refer to a variety of one species he thought was in the process of becoming a new species: “I believe a well-marked variety may be justly called an incipient species.” [2] Take note, he looked at a current organism of a species and predicted that it was busy evolving into a new species that would become apparent in the future.
In 1940, geneticist Richard Goldschmidt argued that “the facts of microevolution do not suffice for an understanding of macroevolution.” He concluded, “Microevolution does not lead beyond the confines of the species, and the typical products of microevolution, the geographic races, are not incipient species.” [3]
This means that minute changes only occur within a species (genetic diversity where finches developing thicker stronger beaks still stay finches.) These small variations cannot be used to explain how the finches are slowly evolving into toucans and will eventually lose their feathers, grow teeth and develop into huge bats… We have an article explaining the different types of evolution here to help clarify what macroevolution is, but note that the term “microevolution” should more accurately be called “genetic diversity” within a species.
But how can we possibly know whether an animal with varieties is in the process of becoming separate species? It should be obvious that Darwin’s term incipient species is a theoretical prediction and can’t be counted as evidence.
C) Origin of a New Species?
We sometimes see that scientists have “finally observed the origin of a new species” in the media. Such cases, however, are invariably either examples of incipient speciation [remember, not evidence but theoretical prediction], or cases in which scientists have inferred from already-existing species how they might have split in the past. Observational evidence for primary speciation is still missing.
In 1996, biologists Scott Gilbert, John Opitz, and Rudolf Raff wrote:
“Genetics might be adequate for explaining microevolution, but microevolutionary changes in gene frequency were not seen as able to turn a reptile into a mammal or to convert a fish into an amphibian. Microevolution looks at adaptations that concern the survival of the fittest, not the arrival of the fittest.” “The origin of species — Darwin’s problem — remains unsolved.” [4]
D) Is there Evidence of Primary Speciation?
Alan Linton is an English bacteriologist who was determined to find evidence of primary speciation and finally concluded in 2001:
“None exists in the literature claiming that one species has been shown to evolve into another. Bacteria, the simplest form of independent life, are ideal for this kind of study, with generation times of twenty to thirty minutes, and populations achieved after eighteen hours. But throughout 150 years of the science of bacteriology, there is no evidence that one species of bacteria has changed into another… Since there is no evidence for species changes between the simplest forms of unicellular life, it is not surprising that there is no evidence for evolution from prokaryotic [e.g. bacterial] to eukaryotic [e.g. plant and animal] cells, let alone throughout the whole array of higher multicellular organisms.” [5]
In 2002, evolutionary biologists Lynn Margulis and Dorion Sagan wrote,
“Speciation, whether in the remote Galápagos, in the laboratory cages of the drosophilosophers [those who study fruit flies], or in the crowded sediments of the palaeontologists, still has never been directly traced.” [6]
Concerns within some published works:
A paper on Science Direct says:
“Sympatric speciation is the evolutionary divergence and reproductive isolation of sister species arising from a single ancestral species in the absence of any barriers to gene flow. As such, this apparently rare phenomenon offers important insights into the role of selection in driving speciation.” [7]
What insights did they gain from this rare phenomenon that has not been observed?
Some articles tend to oversell any potential new evidence for this topic. For example, in an article from Wikipedia, they have written the following sentence: “And even more recently, concrete examples of sympatric divergence have been empirically studied.” Their references were only two articles – one on types of palms (plants) on an island [8], and the other about an infection “possibly” causing unequal hybrid fitness in fruit flies [9]. When someone reads “concrete examples of sympatric divergence”, they will not think about palm trees and infected fruit flies. In the corporate world, this would count as false advertising.
Conclusion
After hearing from geneticist Richard Goldschmidt, biologists Scott Gilbert, John Opitz, and Rudolf Raff, bacteriologist Alan Linton, and evolutionary biologists Lynn Margulis and Dorion Sagan, is it not obvious that Darwin’s term “incipient species” is a theoretical prediction, and not evidence? There has been no evidence found in nature or observed in a lab that one kind of animal is evolving into another kind by gradual, minute changes (mutations).
Douglas J. Futuyma himself said,
“…there is still no evidence that single mutations are responsible for the multiple character differences that typify most genera or other higher taxa.” [10]
A core belief in Darwinian Evolution is that animals evolved to adapt to their environment, and those that adapted the best, survived to reproduce; this is the lynchpin of mutation and natural selection. See what the previously mentioned article on National Geographic says:
“The demands of a different environment or the characteristics of the members of the new group will differentiate the new species from their ancestors.” [1]
However, when several near-identical species occupy the same geographical area at the same time, the question becomes why they evolved differently within the same environmental pressures. Why, indeed. Perhaps they didn’t evolve at all and were designed exactly as they are.
References:
[1] https://education.nationalgeographic.org/resource/speciation/
[2] Darwin’s Origin of Species: second British edition (1860), page 52
[3] Goldschmidt R (1940) The material basis of evolution. Yale University Press, New Haven, Connecticut
[4] Scott F. Gilbert, John M. Opitz, and Rudolf A. Raff, “Resynthesizing Evolutionary and Developmental Biology,” Developmental Biology 173 (1996), 357-372.
[5] Alan H. Linton, “Scant Search for the Maker,” The Times Higher Education Supplement (April 20, 2001), Book Section, 29.
[6] Lynn Margulis and Dorion Sagan, Acquiring Genomes: A Theory of the Origins of Species (New York: Basic Books, 2002), 32.
[7] Sympatric Speciation in the Genomic Era. https://www.sciencedirect.com/science/article/abs/pii/S0169534717302859
[8] Sympatric speciation in palms on an oceanic island – https://www.nature.com/articles/nature04566
[9] Asymmetrical Reinforcement and Wolbachia Infection in Drosophila https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0040325
[10] Douglas J. Futuyma, 2017. “Evolutionary biology today and the call for an extended synthesis”, Article section 2. https://royalsocietypublishing.org/doi/full/10.1098/rsfs.2016.0145
