Convergent Evolution: A Better Explanation

 

The Major Convergent Evolution Obstacle: Can an Event Acknowledged as Improbable Occur Many Times?

by Jerry Bergman, PhD

An international team of scientists working with a certain kind of butterfly in Panama was faced with a question: How could “pairs of clearly unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?”[1] Typically, evolutionists explain this phenomenon away with an empty phrase: “butterflies can evolve along separate and different paths to arrive at the same color pattern, a process called convergent evolution.”[2] This answer requires a suspension of disbelief. How can different species take two very different genetic paths – which would require many major genetic differences – and yet arrive at the same end result?

The “convergent evolution” solution fell apart in a study on Heliconius butterflies published in Current Biology. The Smithsonian Tropical Research Institute remarked that the discovery “forever changes the way evolution is understood.”[3] The finding that motivated this remark is as follows:

although natural selection channeled phenotypic convergence [i.e., outward appearances were similar], divergent developmental contexts between the two major Heliconius lineages opened different developmental routes to evolve resemblance. Consequently, even under very deterministic evolutionary scenarios, our results underscore a surprising unpredictability in the developmental paths underlying convergence in a recent radiation.[4]

Natural selection can, in other words, cause two animals to converge so they look alike (the process called “convergent evolution” noted above), but it can take very different genetic paths to reach that goal. It’s as if two balloons can leave Detroit at the same time, moved by the same wind, but one goes east, the other northwest and they both end up in Paris at the same time. How can this be considered possible? The review uses word salad to basically restate their faith in natural selection’s ability to work miracles.

Evolution is often viewed as a highly contingent process, where chance mutations and random genetic drift affect future outcomes. Nonetheless, there are many cases across branches of the tree of life where different species have evolved remarkably similar solutions to common environmental challenges. Such convergence provides some of the most compelling evidence of the power of natural selection to shape phenotypic diversity in highly deterministic ways. Over the past several decades, numerous studies have examined how convergent change is achieved.[5]

The article concludes, “The broad consensus emerging from these studies is that the path taken by evolution is often repeatable among closely related species but becomes more unpredictable when species are deeply divergent.” In other words, neither natural selection, nor convergent evolution, can explain the final results the study found. This study has eloquently shown that classical evolution theory has a major problem. My conclusion is that convergent evolution, although widely accepted, is wrong.

Professor Doolittle once said that convergence claims are confusing for several reasons, one of which is that often “not enough care is taken to state exactly what kind of convergence one has in mind.” He adds that evidence of “genuine [genetic] sequence convergence has yet to be made.”[6] Genetic sequence convergence is where genetic comparisons show close similarity. What was found in the butterfly study was major genetic differences although the genes for wing color patterns were close to identical.

The authors of the Current Biology paper compared genes between unrelated Heliconius butterflies that nevertheless ended up looking uncannily similar. This undermines the whole convergence argument. There was no genetic convergence and, as we do more genetic comparisons, we will no doubt find many more examples of lack of evidence for genetic convergence in cases where “convergent evolution” has been the consensus explanation. Although claims of convergent evolution are common, even ubiquitous, their identification, interpretation, and explanation are controversial. This line of research will make them even more controversial.[7] Genetic comparisons may well falsify the general theory of convergence.

Why Convergent Evolution Does Not Explain Similarities

Darwinists face a clear and formidable question: how can two animals, with very different ancestries, evolve to become almost identical? It is no small problem. Evolutionists waved it away with the hands of the clock, by claiming gradual evolution takes a long time. Convergence moves slowly as the two species move towards the same goal of becoming more alike as time flows forward. Wikipedia lists over 300 examples of convergent evolution.[8]

An amazing example of unrelated similarity is the marsupial Tasmanian wolf (Thylacinus cynocephalus) which strongly resembles the placental wolf (Canis). Evolutionists claim that the Tasmanian “wolf” is believed to have evolved in Australia, and the placental wolf in North America. They evolved separately along different paths from very different ancestors to coincidentally end up very similar.

The Tasmanian wolf is sometimes called the Tasmanian tiger. It looks much like a dog, but has stripes on its back like a tiger, and resembles a large cat, a fox, or a wolf. It was once thought extinct, but some recent sightings have been reported in the news. This animal complicates the convergent evolution narrative because of its similarities to three animals.[9]  Like the platypus, another Australian marsupial, it seems like a mosaic of multiple animals.

Thylacinus cynocephalus means “pouched animal with a dog’s head.” The main issue involves their reproductive styles, which are totally different. One is a placental mammal, the other a marsupial. And yet this marsupial’s head and the placental dog’s head have very similar skull morphology. Their resemblances in overall shape, locomotory mode, feeding and foraging are also all very similar. Both also have large canines and grinding molars. The behavior and lifestyles of the North American wolf and the Tasmanian wolf are very similar. The only answer evolutionists can give is “convergent evolution,” an empty phrase masquerading as an explanation.

The placental wolf and the marsupial Tasmanian wolf are actually more similar to each other morphologically than a St. Bernard is to a chihuahua. When the Placental wolf and Tasmanian wolf are examined side by side by experts, differences can be seen, but most of the major skull traits and their overall shape are almost identical. “Convergence” attempts to explain away a serious dilemma for Darwinism, namely, how could two animals that are so far apart on the evolutionary tree, and must have diverged from a common ancestor eons ago, end up so similar in so many critical aspects today?

Unhappy Evolutionists

Some biologists have effectively argued against the convergent evolution theory for very good reasons. A major complaint is that it acts as like a post-hoc armchair explanation. Another is that it lacks a mechanism. Another is that it lacks historical evidence. We have no fossil record showing the evolution of the placental wolf from some hypothetical ancient ancestor animal in North America. Nor do we have evidence of the evolution of the Tasmanian wolf from some hypothetical ancient ancestor in Australia. We just know from the evidence that lots of placental wolves live in North America and lots of Tasmanian wolves live in Australia and, in general, no fossils of marsupial wolves are found in North America and no fossils of the placental wolves are found in Australia.

If large numbers of Tasmanian wolf fossils were found in North America beside living placental wolves, evolutionists would be ready with a different story. They could say both evolved here and split off recently, with the former having migrated to Australia. No matter what the facts show, evolution is always the answer.

A Time Bomb

Another major difficulty with convergent evolution as an explanation for the placental wolf and the Tasmanian wolf is that their common traits are far too similar to have evolved separately from different ancient common ancestors way back in the early Cretaceous, as evolutionists believe. Such a huge time span should have produced far more differences than observed. Many other examples of convergence also show commonalities in so many ways that only experts can see the distinctions.[10]  Evolutionary paleontologists often have difficulty determining

whether organisms shared a characteristic because they inherited it from a common ancestor, or because they evolved it separately by convergence. This sometimes makes reconstructing fossil history difficult. Sometimes in the fossil record a species appears to have become extinct then reappears. Is it because the species was rare for a long time, then reappeared in greater abundance (what paleontologist David Jablonski calls Lazarus taxa, because they appeared to rise from the dead), or because another lineage evolved similar features by convergence, and it just looked like a reappearance (what paleontologist Douglas Erwin calls Elvis taxa)?[11]

The theory of convergence has additional problems. “Natural selection” is the Darwinians’ magic wand to explain everything, including convergence, but science should be open to other theories that can explain things. The major difficulty by far with convergence is how random mutations and natural selection could repeatedly generate the same complex designs requiring many genes, sometimes several scores of times. If Darwinists were not so antagonistic to skeptics of their theory, they might be open to evidence of an intelligent Creator using the same design in different contexts.

Convergence Theory Hinders Science

Svante Pääbo, after decades of research, wrote that convergence makes taxonomy difficult. He wrote that the many “examples of convergent evolution was to me a strong message that morphology is often an unreliable indicator of relatedness among organisms.”[12] Professor Lima-de-Faria, in an extensive study of convergent evolution, concluded that the striking similarities in very different life-forms is a “puzzling fact” not explained by Darwinism. Indeed, he believes, similarities between unrelated organisms are a major obstacle for evolution theory.[13] The esteemed evolutionist George Gaylord Simpson stressed that “the phenomenon of evolutionary convergence… is a source of disquiet and precaution to paleontologists and other biologists.”[14]

Some evolutionists try this angle: living in similar environments and experiencing similar selection pressures can produce convergence, they argue.[15] This is called the “adaptationist” theory of convergence. Comparing the adaptationist and constraint perspectives on convergent evolution, evolutionists considered

the more fundamental question about the predictability of evolutionary change. More generally, convergent evolution has long been taken as evidence of adaptation, but some recent workers have questioned the ability of evolutionary biologists to infer the operation of natural selection from the phylogenetic pattern.[16]

Mindless Environments Cannot Force Convergence

There is no necessary connection between the environment and convergence. Environments of “convergent” animals are often very different. Except for opossums and their relatives, marsupials are now found only in Australia and New Zealand. The environments of North America and Australia are very different in climate, terrain, and, especially, in the life-forms inhabiting the land, and yet both America and Australia have opossums.[17]

Conversely, environments of unlike animals are often quite similar. No reason exists to believe similar environmental demands could evolve two very different precursor animals to converge into animals with similar traits. Nor does any direct evidence exist that even very similar environments will evolve different animals to increasingly resemble each other until they become, not just superficially identical, but in many ways, close to physiologically identical. In conclusion, convergence theory has launched many disputes in the past between evolutionists, and new research has only added to their headaches.

Sharing: A Much Better Explanation

Possibly due to the inadequacy of convergent evolution, another (and much better) explanation has been offered for convergence: shared information. Animals can pass genes back and forth in a process known as introgression, defined as “the introduction of genes from one species into the gene pool of another species, occurring when matings between the two produce fertile hybrids.” In the case of the Heliconius butterflies, the researchers are claiming that rampant introgression has occurred.[18]

Another example shows up in the human gene pool. Geneticists writing in a preprint in bioRxiv on November 15 found that “Neanderthal introgression reintroduced functional ancestral alleles lost in Eurasian populations.” Nothing new evolved; the information was “reintroduced” to Eurasions through introgression.

Even so, explaining the variety by the exchange of genes due to interbreeding between genetically divergent individuals does not solve the evolutionary origins problem. What needs to be explained is the origin of the functional genes that are passed around by introgression. As any dog breeder knows, the exchange of genes produces an enormous amount of variety. Hollingshead opined: “On a grand scale, the findings provide evidence that the model of an evolutionary tree first famously drawn by Darwin may need some adjusting.”[19]

The Creation Explanation

Actually, this is what creationists have been saying for decades: a great deal of the variety in the natural world is the result of sharing of genetic information, not emergence of new genetic information by random mutation and natural selection. Sharing of pre-existing genetic information can occur by several methods, including horizontal gene transfer, retrovirus insertions, hybridization, interbreeding and introgression. Creation taxonomists organize life by “created kinds” (baramin), within which a good deal of horizontal diversification and genetic sharing can occur. For example, the cat kind includes lions, cheetahs, domestic cats, etc. – a total of 30+ living species and a number of extinct ones. These all came from the original pair of cats, Purdom and Hodge argued in a 2008 paper.[20]

With evolution a theory in crisis, particularly when it comes to convergence, openness to alternative explanations is in order.

 

References

[1] Is Evolution Predictable? Butterflies take different paths to arrive at the same color pattern. Smithsonian Tropical Research Institute, 14 November 2019. https://stri.si.edu

[2] Ref. 1.

[3] Ref. 1.

[4] Carolina Concha, et al., 2019. Interplay between Developmental Flexibility and Determinism in the Evolution of Mimetic Heliconius Wing Patterns. Current Biology, 29: 1-14, December 2; DOI: 10.1016/j.cub.2019.10.010.

[5] Ref. 1.

[6] Doolittle, R. 1994. “Convergent Evolution: The Need to be Explicit.” Trends in Biochemical Sciences, 19(1):15-18, p. 15.

[7] Losos, J. B. 2011. “Convergence, Adaptation, and Constraint.” Evolution, 65(7):1827-1840.

[8] Wikipedia: List of examples of convergent evolution. https://en.wikipedia.org/wiki/List_of_examples_of_convergent_evolution.

[9]  Woodward, Aylin. The Tasmanian tiger is thought to have gone extinct in 1936, but mysterious sightings suggest the creature might still be out there. https://www.businessinsider.com/tasmanian-tiger-may-not-be-extinct-sightings-pictures-2019-11.

[10] Simpson, George. 1980. Splendid Isolation: The Curious History of South American Mammals. New Haven, CT: Yale University Press.

[11] Rice, Stanley. 2007. “Convergence,” pp. 89-93 in: Encyclopedia of Evolution. New York, NY: Facts on File, p. 93.

[12] Pääbo, Svante. 2014. Neanderthal Man: In Search of Lost Genomes. New York, NY: Basic Books, p. 66.

[13] Lima-de-Faria, A. 1988. Evolution without Selection: Form and Function by Autoevolution. Amsterdam, Holland: Elsevier, p. 271.

[14] Losos, J. B. 2011; Simpson, 1980, pp. 12-13.

[15] Milner, R. 1990. The Encyclopedia of Evolution. New York, NY: Facts on File.

[16] Rice, 2007; Losos,  2011, p. 1872.)

[17] Johnson, D. H. 1955. “The Incredible Kangaroo: Australia’s Famous Marsupial Sits on Its Tail, Fights Like a Man, Bounces Like a Steel Spring, and Graces a Coat of Arms.” The National Geographic Magazine, 108(4):487-500, p. 489.

[18]  Reuell, Peter. 2019. A Clue to Biodiversity. https://news.harvard.edu/gazette/story/2019/10/gene-flow-between-butterfly-species-offers-clue-to-biodiversity/; Nathaniel B. Edelman. 2019. Genomic architecture and introgression shape a butterfly radiation. Science. Science  01 Nov 2019. 366 (6465): 594-599. Online at https://science.sciencemag.org/content/366/6465/594.full.

[19]  Hollingshead, Todd. 2019 Analysis of butterfly genomes reveals answers to complex evolutionary history questions. https://lifesciences.byu.edu/researchers-break-down-20-whole-genomes-of-perplexing-butterfly-to-find. October 31.

[20] Purdom, Georgia and Bodie Hodge, 2008. “Zonkeys, Ligers, and Wolphins, Oh My!” Answers in Depth, Vol.3, pp.71–73. https://assets.answersingenesis.org/doc/articles/aid/v3/zonkeys-ligers-wolphins.pdf .

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Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology at several colleges and universities including for over 40 years at 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 1,300 publications in 12 languages and 40 books and monographs. His books and textbooks that include chapters that he authored, are in over 1,500 college libraries in 27 countries. So far over 80,000 copies of the 40 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.