This is Part 1 of a three-part series about the mule, the hybrid problem in science, and ways in which Darwinism and the Jewish Bible illuminate each other. You can find the other parts here:
- Part 2: Anah’s Mule and Torah’s Darwinian Experiment
- Part 3: A Fertile Hybrid: Torah’s Quantum Theo-biological Solution to Darwin’s Problem
“Evolutionary theory coincides with the lofty doctrines of Kabbalah more than any other philosophical doctrine.” – R. Avraham I. Kook (1921)1
“[We may bring proof] from natural scientists for it is permissible to learn from them, for God’s spirit speaks through them. ” – R. Israel Lifschitz (1842)2
” [Man cannot] search too far or be too well studied in the book of God’s word, or in the book of God’s works; divinity or philosophy; but rather let men endeavour an endless progress or proficience in both.” – Francis Bacon, Advancement of Learning, (1605) quoted as an epigraph to Darwin’s Origin of the Species
““The modern synthesis is remarkably good at modeling the survival of the fittest, but not good at modeling the arrival of the fittest.”3
Torah and Darwin share a mule problem.
Darwin admired mules in general and his own mule in particular, but as hybrids between horses and donkeys, like all other animal hybrids, they’re sterile. The apparently universal sterility of hybrids posed a fundamental challenge to his theory of how new species arise. Darwin stated the problem succinctly:
“How can we account for species, when crossed, being sterile and producing sterile offspring, whereas, when varieties are crossed, their fertility is unimpaired?4
If only two individual varieties of the same species can reproduce but two individuals from different species never can, then how does a new species ever arise? Combined with the other great paradox – that no “transitional” species had ever been observed – Darwin saw nearly-fatal gaps in his theory that even today continue to present insoluble paradoxes for evolutionary biology.5
Surprisingly, the Jewish Bible also struggles with the mule in remarkably similar ways. Though only one mention is made of mules in the Five Books of Moses, that single instance challenges its sense of cosmic order. The mere existence of the mule violates categories of order and acquires surprisingly powerful – and negative – transcendental significance. The Torah abhors mixing species and has several injunctions against it, including some that carry the death penalty. The very fact of the existence of the mule is so transgressive that later commentators in the Talmud tell the story that just at sundown before the very first Shabbat, in the very last moments of Creation, God considers showing Adam the idea of mule breeding along with other scientific secrets, but decides not to. The implication of the sages is that it is too abhorrent.
For both Darwinian science and traditional Jewish theology, the mule stands on the border between two versions of cosmic order. If God created all the different species and constrained them to be fertile only within their type (for good metaphysical reasons of His own), then the mule is a violation of this order. If, on the other hand, species emerge and proliferate over time on their own, interbreeding and evolving in order to create new ones without divine intervention, then how come hybrids like the mule are always infertile?6 Though the proliferation of species from earlier forms is obvious, evolutionary biology seems to stop at a wall erected by some force beyond what its current paradigm can explain.
As Darwin and Torah wrestle with their mule problem, they have some profound things to say to each other. After all, Torah and science share the same world and both are good faith attempts to explain it, and though they serve different premises about how that world exists and why. it should not be surprising that they have mutually illuminating things to say to each other.7
In what follows, I am not refuting or questioning evolution or its general picture of the evolution and proliferation of species. But I do focus on frailties and important unanswered questions about how, precisely, speciation occurs that leave the door open to considering an alternative model, one I address in Part 3 of this series of blogs.
The Mule Paradox in Darwinian theory
In the first paragraph of the Origin of Species (1859), Darwin says the inspiration for his scientific quest was to “throw some light on… that mystery of mysteries.”8 He was quoting his teacher, the genius John Herschel, who was amazed that no one in all history had ever observed the first appearance of new beings on earth.9 If we could ever observe and explain the mechanics of how new species arise and replace extinct ones, Herschel said, nature would be caught in the act of creation on its own without intervention from a supernatural Power working miracles. Furthermore, it would answer what he thought was the simpleminded religious notion that all species were fixed at the beginning, boarded Noah’s ark, and populated the Earth with the splendid variety we now clearly see. Yet, to his dismay, science had never yet witnessed the rise of a new species, nor explained in an empirically provable way how it might happen, nor even been able to identify an example of a fertile “transitional species.”
From 1826-1846, Darwin journeyed three times on the HMS Beagle to isolated lands like Australia and the Galapagos islands. At first, his goal was geological survey, but along the way he also catalogued all sorts of exotic animals, including the rat-kangaroo, new beetles, plants, turtles, marine animals, and most famously what he described as fourteen new “species” of finches that arose from a common ancestor. In Origin of the Species, Darwin then speculated – elaborately, logically, brilliantly and thoroughly – the biological mechanisms that could have produced this astounding variety of lifeforms.
Darwin’s solution, evolution by natural selection, is now scientific gospel. It makes perfect sense: when the environment changes, it puts new pressures on an organism. Individuals that can’t survive in these new conditions die. New species emerge because they start showing or developing traits that give them an advantage to survive. These traits may have been minor or old, long-hidden ones that come into play in new conditions. Other traits may arise by accident (what we now call mutation). When a short-beaked finch flies to an island where it first finds long-needled cactuses are a major food source, a longer beak enables it to eat. More fit than their peers, a fractionally longer-beaked finch live in greater numbers to pass their advantages to a new generation, which in turn may amplify their success, while their disadvantaged siblings die out. Over vast stretches of time, these individual variations of an old species become so sufficiently different that they form a new species.
However, one of the most serious challenges to his own scheme was the sterility of all known hybrids, exemplified in the mule: “[A] cross between two forms … produce hybrids which are almost always in some degree sterile.” He was at a loss to explain how to solve this mulish conundrum, though he offers various interesting and rational hypotheses. He postulated that new species were likely to arise in remote, protected places, in “reproductive isolation” like the Galapagos. He even prophetically speculates that some sort of microscopic particle might be involved in transmitting new features from generation to generation, even though knowledge of DNA and genetic mutation wouldn’t come for another century
Darwin devoted a whole chapter (Chapter XIII in the first edition; IX in later editions) to hybrids, though never explicitly states the paradox their sterility implies. I will try to do so here:
Classically, a new species is defined by the fact that they cannot successfully mate with other species, even ones they are closely related to or descended from.10 But if an old species (imagine a wolf) on the road to evolving into a new species (call it a dog) gives rise to a wolfdog, and that wolfdog cannot mate with other hybrid wolfdogs productively, then how do new species ever start? It doesn’t matter that the new species offers advantages for survival of her offspring to her betrothed of the old species – like the superior vigor and stamina of Darwin’s own mule. There always is some other mysterious genetic barrier that prevents the success of their new line. This is still evolutionary theory’s Catch-22.
Evolutionary science today still struggles with the Mule Paradox
Today, 150 years after Darwin first published his theory, the mule continues to bedevil evolutionary biology on questions so fundamental and essential that we can fairly say that Herschel’s original mystery of mysteries remains unsolved. There are excellent full-fledged reviews of these issues from both sides,11a but I will summarize them here within the frame of the mule problem to establish the terms of a dialogue between Darwinian science and Torah.
Lack of conclusive examples: The second greatest challenge to Darwin is that in the intervening century and a half, conclusive observation and definition of a new, fertile species as opposed to an exotic offshoot of a common ancestor is still hard to find. Though there are many fertile plant and fruit hybrids, but no discussion of whether they are backwards interfertile enough to be called a new species, and biology has failed to find clearly convincing examples in the animal world. The few examples of robust animal hybrids seem to lie in an ambiguous zone between hybrids and vastly different expressions of the same species (like chihuahuas and mastiffs). Darwin, by the way, had the same issue with the definition – taxonomy – of exactly how much difference a creature needed to show before it constituted a distinct species. In his first edition of 1853 he writes, “I was much struck how entirely vague and arbitrary is the distinction between species and varieties” and in later editions he devotes a whole chapter to the problem.12
Lack of a clear-cut definition of what a new species is as opposed to an exotic variety of the same species: Modern biology and zoology continue to have the same problem Darwin did.13[xiii] There is no universal, precise, stable definition of speciation that sticks. For instance, Darwin induced that the fourteen different varieties of finches he observed on Galapagos islands were probably derived from a common ancestor that flew to the islands from the mainland long ago. But as we recently discovered, these new species can interbreed and even mate with their ancestral variety productively. Technically, they’re just distantly related varieties of the same aboriginal species. They don’t generally interbreed because of a cascade of behaviors that creates a tendency to prefer their own – they develop their own tribal mating songs, tend to occupy distinct territories, etc. In human terms we might call this intimacy or familiarity or tribalism. An anthropologist might call it “endogamy” (the taboo against marrying outside your tribe).14
We don’t understand even at the genetic level why all animal hybrids are infertile: Genetic research to define and confirm evolution of new species is very far advanced. Geneticists have sequenced the DNA of thousands of species and compared them in order to map the overlap between species and within them. By this means they then trace changes or mutations in specific sequences of DNA, correlate them to specific traits, and define what made a new species diverge from its parent or brother species. Yet even at the level of genetic research and theory, it remains a mystery as to why hybrids are infertile. In the two million catalogued species of organisms, only a few of these hypothetically fertile hybrids have been identified, and even scientists hedge their bets, calling them “putative” (i.e. “so-called” or alleged).15
Do fertile hybrids exist at all, even in the vegetable kingdom? While no certain example of fertile animal hybrids are known, biologists have agreed to recognize certain fertile hybrid plant varieties as genuinely new species. Nonetheless, even these new species are spurious, since the mechanism, genetic stability, and even the definition of these plants as new species are still in doubt. As the title of one recent article in Evolutionary Applications (2016) asks, “What, if anything, are hybrids?”16
Even if fertile hybrids exist, how they constitute proof of evolution is in doubt: Further, researchers admit that even if examples of fertile hybrid species can be found, the importance of hybridization as a way to produce new species is still widely debated (ironically because at first classical evolution science discarded it as essential proof), and we lack a general understanding of the conditions most likely to generate them.17
Potentially, a good measure of speciation exists, but scientists can’t agree on that measure and no examples can be found that satisfies any measure: In the absence of other empirical measures of speciation, genetics offers a sensible, empirical solution: establish a quantitative measure of genetic “distance” or “divergence” between organisms – some quotient of the load of DNA molecules and number of discrete genes where such mutations occur – that would define a new species. However, agreeing to any such exact number runs up against the same definitional mule problem: no examples have yet to be found of animal species that are sufficiently genetically different and are also interfertile.18 More fundamentally, any threshold of genetic divergence relies on a clear definition of what makes two species different. As one theorist puts it, “genetic divergence is not free of assumptions about the nature of species or speciation.”19
Finally, purported new species have a bad habit of regressing to old new ones by backwards or cross-species interbreeding: To make the picture even muddier, nature isn’t cooperating with speciation. As time goes on grow, alleged new species have a bad habit of reverting to older forms or worse, dying out when human intervention (“domestication”) is withdrawn. This disturbing new trend is called “speciation reversal.20 Darwin was well aware of this problem and flagged it in Chapter I of his first edition of Origin of the Species (1859). In the intervening century and a half, biologists have concluded that a new variety of creature is so different from its cousins or ancestors that it constitutes a new species. However, over time they have had to walk back their declaration in almost every single important case.
- Wolves are the ancestors of dogs. Dogs are the result of a hundred thousand years of human breeding and selection of more domesticated desirable wolfish traits, mimicking and speeding up the process of “natural” selection. Traditionally, they were labeled as two different species. However, dogs and wolves interbreed quite well, to the point that science now counts them as relatives within the same species family.21
- Ravens, which supposedly split into two different species over a million years ago, have the same problem.22
- Polar bears and grizzlies, also once thought to be two distinct species, are interfertile and show signs of de-speciating.23
- Alpine whitefish, too, are getting smoked.24
- Even Darwin’s major original examples of the hypothetical new species he found arising in isolation in the Galapagos islands, like his famous tortoises and finches, have both been found to undergo species reversal, or “de-speciation” in recent studies.25
These reversals are not isolated examples but constitute the rule rather than the exception. Kevin Omland, who has studied the problem for twenty years, claims, “It’s probably happened in hundreds or almost certainly thousands of lineages all over the planet.”2627They are further disappointing because species that were touted as proof of the Darwinian model now constitute counter-proof. Together they suggest that there’s a fundamental uncertainty not only in definitions of what constitutes a new species but whether speciation is even possible through hybridization, despite what our senses tell us is obvious about biodiversity.
All these problems with Darwinian theory, even at the molecular level, resolve into the Mule Paradox: by definition, two species are distinguished from each other because they’re unable to breed. Yet, any attempt to breed two different species leads to sterile progeny or false examples. Any other examples we thought we observed in nature of the result of such hybrid breeding, absent understanding or witnessing the process, turn out to be relatives of the same form by reverting to their common ancestral form.
Evolution powerfully explains the obvious diversity of species on Earth, but it has yet to find a fertile mule – or a genetic model of hybrid fertility – that would explain how they actually arise. As John Whitfield quips in his article about “Postmodern evolution” in the science journal Nature, ““The modern synthesis [of Darwinism] is remarkably good at modeling the survival of the fittest, but not good at modeling the arrival of the fittest.”28
Science is always a dance between what we’ve explained and what we’ve yet to explain, the known and the not-yet-known, not to mention all those unknown unknowns we haven’t even discovered. We can hope that the combination of genetics and patient observation of nature’s changes over vast scales of time will finally fill in these gaps in our understanding and perhaps even confirm Darwin’s theory.
But it may also be true, as the evidence above suggests, that Darwin’s particular theory of speciation is also a mule, epistemologically speaking. Science is supposed to work not as dogma but as skepticism even about its own most dearly held beliefs. And science also proceeds by sudden paradigm shifts that come from imagining new ways to frame our view of the cosmos. Very occasionally, science has to reframe its entire model of the world, the epistemological equivalent of punctuated evolution. Before I suggest a way that the Hebrew Bible may offer such a re-framing in Part 3, I’d like to prepare the way by showing how a Darwinian perspective on hybrids and mules helps frame what I call the Bible’s own version of the “Mule Problem,” the Torah’s aversion to interbreeding species, especially human species in Part 2: Anah’s Mule and Torah’s Darwinian Experiment. Part 3 (to come) takes the intractable problem of the mule, of hybrid sterility, as an invitation to think towards a different paradigm of evolution involving variation within fixed categories. I suggest that Torah’s view of breeding and evolution points to a possible solution to biology’s problem, a new paradigm, by taking a not-completely unscientific bio-metaphysical approach.29
David’s personal note:
I got my undergraduate degree long ago (1973) in molecular biology from MIT. I spent hours pipetting and centrifuging beta-tagged thymine DNA as an undegrad research assistant to Prof. Joel Huberman, looking at the Okazaki Fragment Theory. Okazaki Fragments are smaller pieces of DNA that enable replication to proceed from both ends of smaller fragments (3′ and 5′ ends), making it more efficient than replicating whole long strands in one direction only and though for a time before I left the lab, I thought the fragments were more the result of how I was mishandling the samples, in the decades since, Okazaki Fragment have become an important way of understanding how genetic replication happens so efficiently.
I mention these bona fides to convince you that I am not trying to wade into a tiresome debate on the side of creationism, nor am I trying to refute evolution, nor deny the empirical or epistemological power of healthy science. I am sure the fact that I both challenge evolutionary gospel and try to talk meaningfully about Jewish belief will make me appear to some to be just another anti-science postmodernist. On the other hand, I fear that literalists will recruit this blog for the religious side anyway, even though it will also simultaneously be rejected by many traditional Jews.
I believe in both the God revealed to us by Torah and science. If I am accused of misrepresenting either or both legitimately and not on ideological grounds, I apologize in advance. Like several prominent Orthodox Jewish thinkers (Maimonides, Soloveitchik, Kook) I see science as potential fulfillment of Torah.
I also note we have been living for about two centuries in an aberrant parentheses. In all of human history, ours is the only time when the reigning episteme of our culture desacralizes the picture of the cosmos – takes God out of the picture – as a matter of fundamental belief.
In these blogs, I point out problems with evolutionary theory, but these are serious problems described and acknowledged by science itself. I also unabashedly believe the Torah is a source of great truths, but I believe our understanding of the Torah’s description of the creation of the cosmos is unfolding, like nature itself. In my quantum cosmological view, Nature requires God’s sustained and intimate attention to every quantum event in order for reality to unfold or blossom into being. Similarly, human understanding of what the Torah says about the cosmos is revealed in fertile interaction with God’s Mind as transcribed (written) and transmitted (orally) in the Torah. The Hebrew Bible describes a God that encourages science and the ongoing deepening of our knowledge about the cosmos. It also encourages the ethical exploitation of nature through technology to improve the human condition.
It’s tragic that Darwin’s theory has become the center of a divisive debate at all between religion and science. Darwin wrote his magnificent books On the Origin of the Species and The Descent of Man when the distance and separation between natural philosophy and theology were not as great as they are today. Darwin meditates on the relationships between humans, the rest of nature, and the Divine, even though he himself was probably an agnostic, at best, when he wrote them. Consider this passage from Origin of the Species (Chap VIII):
“He who believes that each equine species was independently created, will, I presume, assert that each species has been created with a tendency to vary, both under nature and under domestication, in this particular manner, so as often to become striped like the other species of the genus; and that each has been created with a strong tendency, when crossed with species inhabiting distant quarters of the world, to produce hybrids resembling in their stripes, not their own parents, but other species of the genus. To admit this view is, as it seems to me, to reject a real for an unreal, or at least for an unknown cause. It makes the works of God a mere mockery and deception; I would almost as soon believe with the old and ignorant cosmogonists, that fossil shells had never lived, but had been created in stone so as to mock the shells now living on the sea-shore.”
Darwin is critical of simplistic traditional creationist thinking about the species, but also points at a higher, more sophisticated idea of God’s artistry in the world.
1.Oret Ha-Kodesh 2:557 (Jerusalem: Mossad HaRav Kook, 1985)
2.Derech Or HaChaim, “A Theological Reflection on Death, Resurrection and The Age of the Universe”), transl. by Yaacov Elman  in Aryeh Kaplan, Immortality, Resurrection and the Age of the Universe: A Kabbalistic View (p. 110) [Hoboken: KTAV. 1993]
3.John Whitfield, “Biological theory: Postmodern evolution?” Nature, 455: 281-284 (September 17, 2008).
4.Origin of the Species (1859) p, 172.
5. See “Interspecies Hybrids Play a Vital Role in Evolution,” (Aug 24, 2017) Quanta Magazine [see https://www.quantamagazine.org/interspecies-hybrids-play-a-vital-role-in-evolution-20170824/ ]
6.Safran, R. J. & Nosil, P. (2012) Speciation: The Origin of New Species. Nature Education Knowledge 3(10):17 https://www.nature.com/scitable/knowledge/library/speciation-the-origin-of-new-species-26230527
7. Both the sages of the Talmud and Darwin described nature and tried to understand the physical characteristics of the mule in very similar discourses. This passage from the Talmud tries to formulate a scientific law based on empirical observations of how breeding of mules work:
- Our sages have said in Bereshit Rabbah 82,14 that any mule, i.e. an animal resembling it traces its ancestry by means of the size of its ears. If the ears are short it has been sired by a donkey and born by a horse, whereas if it has long ears it has been sired by a horse having been born by an ass.
9. In a letter to Charles Lyell as recounted in Tony Vogel Carey, “That Mystery of Mysteries,” Philosophy Now (https://philosophynow.org/issues/105/That_Mystery_of_Mysteries)
10.Although, even this test has serious issues. The Wikipedia entry on “species” gives a good sense of the depth of the problem: “In biology, a species is the basic unit of classification and a taxonomic rank as well as a unit of biodiversity, but it has proven difficult to find a satisfactory definition.” https://en.wikipedia.org/wiki/SpeciesA.
11a. Good places to start are:
A. Ernst Mayr, The growth of biological thought. Diversity, evolution, and inheritance. (Cambridge, MA: Belknap, 1982)
B. Casey Luskin, “The Top Ten Scientific Problems with Biological and Chemical Evolution,” in the volume More than Myth, edited by Paul Brown and Robert Stackpole (Chartwell Press, 2014). Available online here https://evolutionnews.org/2015/01/the_top_ten_sci/.
C. For a very good definition of the entire problem of speciation in Darwin and contemporary evolutionary theory, as well as a counter-argument to this line of reasoning, see James Mallett, “Mayr’s view of Darwin: was Darwin wrong about speciation?” (2008).]
12.“On the origin of species by means of natural selection” . And see the section “Character of Domestic Varieties; difficulty of distinguishing between Varieties and Species; origin of Domestic Varieties from one or more Species” in the sixth edition . He writes in the same chapter, “there are hardly any domestic races, either amongst animals or plants, which have not been ranked by some competent judges as mere varieties, and by other competent judges as the descendants of aboriginally distinct species. If any marked distinction existed between domestic races and species, this source of doubt could not so perpetually recur.’ https://en.wikisource.org/wiki/The_Origin_of_Species_(1872)/Chapter_I, p.12
13. “Baker RJ, Bradley RD, “Speciation in Mammals and the Genetic Speciation Series Concept,” J Mammal. 2006 Aug 1;87(4):643-662. https://www.ncbi.nlm.nih.gov/pubmed/19890476 “… We define a genetic species as a group of genetically compatible interbreeding natural populations that is genetically isolated from other such groups.”
14. Brandon Kim, “How Darwin’s Finches Keep Their Species Separate,” WIRED (Nov 11, 2010) https://www.wired.com/2010/11/darwin-finch-speciation/
15. “Hybridization can promote speciation, and examples of putative hybrid species (emphasis mine) have now been identified across the tree of life.” Aaron A. Comeault and Daniel R. Matute, “Genetic divergence and the number of hybridizing species affect the path to homoploid hybrid speciation, “PNAS September 25, 2018 115 (39) 9761-9766; https://doi.org/10.1073/pnas.1809685115
16. Zachariah Gompert and C. Alex Buerkle, “What, if anything, are hybrids? Enduring truths and challenges associated with population structure and gene flow.” Evol Appl. 2016 Aug; 9(7): 909–923. (Published online 2016 Apr 26. doi: 10.1111/eva.12380)
17.Tina Hesman Saey, “Hybrids reveal the barriers to successful mating between species, Science News (Oct 31, 2017) https://www.sciencenews.org/article/hybrids-reveal-barriers-successful-mating-between-species,
For evidence for successful hybridization leading to speciation in plants, see Daniel Matute, Daniel Ortiz Barrientos, “Speciation: The Strength of Natural Selection Driving Reinforcement,” Current Biology, 24:19 (Oct 6, 2014) https://doi.org/10.1016/j.cub.2014.08.033.
18. See Robert J. Baker and Robert D. Bradley, “Speciation in Mammals and the Genetic Species Concept,” J Mammal. 2006 Aug 1; 87(4): 643–662. See also Payseur, B. A. & Rieseberg, L. H. A genomic perspective on hybridization and speciation. Mol. Ecol. 25, 2337–2360 (2016).
19. J. Willem H. Ferguson, “On the use of genetic divergence for identifying species,” Biological Journal of the Linnean Society, Volume 75, Issue 4, 1 April 2002, (509–516) ,https://doi.org/10.1046/j.1095-8312.2002.00042.x He writes more fully in the abstract: “genetic distance as a species criterion is … not free of assumptions about the nature of species or of speciation … is not parsimonious, its theoretical foundations are not well understood, and it cannot be applied over a wide range of plants and animals.
20. Kip Hansen, “Darwin — We’ve Got a Problem,” WhattsUpWithThat (March 18, 2018) https://wattsupwiththat.com/2018/03/18/darwin-weve-got-a-problem/
21. B. M., onHoldt, Kays, R., Pollinger, J. P. & Wayne, R. K. Admixture mapping identifies introgressed genomic regions in North American canids. Mol. Ecol. 25, 2443–2453 (2016). v.
22. Anna M. Kearns, Marco Restani, Ildiko Szabo, Audun Schrøder-Nielsen, et al. “Genomic evidence of speciation reversal in ravens” Nature Communications v 9 906 (2018) https://www.nature.com/articles/s41467-018-03294-w
23. Miller, W. et al. Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change. Proc. Natl Acad. Sci. USA 109, E2382–E2390 (2012).
24. Vonlanthen, P. et al. Eutrophication causes speciation reversal in whitefish adaptive radiations. Nature 482, 357–362 (2013).
25. Kleindorfer, S. et al. “Species collapse via hybridization in Darwin’s tree finches.” Am. Nat. 183, 325–341 (2014).
26. Garrick, R. C. et al. Lineage fusion in Galápagos giant tortoises. Mol. Ecol. 23, 5276–5290 (2014).
27. Kevin Omland, a professor of biological sciences at University of Maryland, Baltimore County, said this of the phenomenon of species reversal in a news release. https://www.upi.com/When-two-species-become-one-New-study-examines-speciation-reversal/5061520012637/#ixzz5a5CYwkM3. See also his scientific article, Jacobsen, F. & Omland, K. E. Perspective: increasing evidence of the role of gene flow in animal evolution: hybrid speciation in the yellow-rumped warbler complex. Mol. Ecol. 20, 2236–2239 (2011).
“… hybridisation can result in the collapse of formerly distinct lineages or species into a single hybrid lineage with an admixed mosaic genome. This reticulate [divided into a network] pathway is most often referred to as speciation reversal or lineage fusion, and it can occur at all stages of the speciation continuum, effectively ‘reversing speciation’ or causing ‘despeciation’
28. John Whitfield, “Biological theory: Postmodern evolution?” Nature, 455: 281-284 (September 17, 2008).
29. The purpose of this exercise is not to invoke the same old fundamental religious beliefs about the fixity of Creation (creationism), but rather to expose a much deeper pathway to approaching and finding solutions to “the mule problem.” Instead of evolutionary epistemology, call it “scriptural” (or “metaphysical”) epistemology. This is a fancy way of saying that the Torah, has as an obviously non-scientific (although in some ways surprisingly orderly and rational) style of thinking about the order of the cosmos and a way to reconcile contradictions that arise between experience and knowledge. Armed with Torah’s alternative epistemology, we can “think differently” about evolution. Ultimately, this different approach actually may have scientific merit, as certain hints in burgeoning research and theory from quantum biology suggest.“Evolutionary epistemology” is actually a potent school of the philosophy of knowledge. Its assumptions and approaches have profound relationships to the discussion in this essay, especially as contrasted with Torah or the kind of metaphysical epistemology I invoke here, but a full discussion of it would involve more complexity than this essay can treat. See the Stanford Encyclopedia of Philosophy entry on “Evolutionary Epistemology” [https://plato.stanford.edu/entries/epistemology-evolutionary/]