I have no formal post secondary education of note, but I have remained interested in science all my life. I have been lucky enough at times to have been able to work as a professional in scientific and technical fields, although I settled on carpentry when I moved to a rural area to raise children.
In my occasional bouts of research into biology and evolutionary issues, I ran across Stabilization Theory, proposed by Dr. Eugene McCarthy. His book is available online, and is written for laymen, containing well presented and lucid prose laying out how Stabilization Theory explains evolution as the fossil record reveals it.
Darwinian evolution is monophyletelic, or linearly progressing. A founding species evolves into it's posterity via many small changes that add up over time to changes sufficiently large to result in new species. The fossil record is now widely recognized by evolutionary biologists as not supporting this theory.
What the fossil record shows is that species arise suddenly, persist for however long in a stable form, and either remain extant, or go extinct. The gradual, minute changes predicted by Darwinian theory are simply not observed in the fossil record. This is not to say that there are no forms intermediate between other forms at all, but that those intermediate forms do not seem to arise gradually, nor to slowly morph into subsequent species.
Stephen J. Gould proposed the punctuated equilibrium modification of Darwinian evolutionary theory, and that had more support from the record, as it proposed that when species undertook evolutionary change, they did so rapidly under conditions that swiftly encouraged such changes.
One argument that has been made to try to explain why the fossil record does not show gradual evolution of species, is the artifact hypothesis. This hypothesis points out that fossilization is uncommon, and the vast majority of creatures are not preserved as fossils. Since only very few fossils exist compared to how many organisms have not been preserved, and the fact that only a small fraction of fossils are found when they are exposed, the record is incomplete.
No doubt that is true on both counts, and that the fossil record is generally incomplete. But there are extraordinary places where conditions highly conducive to fossilization persisted for long periods of time, and in these places, if the artifact hypothesis is correct, we should expect to find better evidence of gradual morphology.
Again, this is not what the fossil record shows, even where it is orders of magnitude more complete than generally. Both punctuated equilibrium and the artifact hypothesis appear not to be supported by the fossil record. The best and finest fossil beds, some that preserve soft tissues for million of years, and details so fine microscopes are required to see them, continue to show that species arise fully differentiated from their kin, persist over time unchanged, and either expire or are still around.
Well, let's look at living species. There should be examples of species changing right now from one form to another, gradually and observably on the time scale of modern scientific methods. Surprise! There are some.
Particularly where geographically isolated, some species do show ongoing transformations via gradual accumulations of random mutations that preferentially induce survival in the individuals having those traits. In his book "The Beak of the Finch" Jonathan Weiner shows how random variations in the beak morphology of Galapagos Finches cause succeeding generations to inherit beaks different than those of their preceding generations.
Drought causes seed production to cease, and the store of seeds is depleted by the bird populations feeding on them, starting with the softest, tastiest, and most nutritious. As the seeds that are left become more difficult to eat and harder to crack, Finches surviving to produce offspring pass down beaks that are more robust and better suited to using such food. Case closed?
No. When the rains come, seed production springs back into action, and those birds best able to capitalize on the highest value foods turn out to be those most challenged during drought - those with smaller, less robust beaks. The strong beaked Finches are outproduced by more gracile beaked Finches, and Galapagos Finch beaks trend back towards where they came.
This is not speciation. This is stasis over time. Despite the fact that it proves the Darwinian mechanism does in fact exist, and could result in gradual accumulation of morphological changes over time, it does not show that this is actually creating new species. The size of Finch beaks remains within a stable range, and a fossil record would show the species remaining the same over time.
However, there are other ways creatures become morphologically distinct. Dr. Eugene McCarthy has spent his career studying hybridization, and has published the exhaustive "Handbook of Avian Hybrids of the World", considered to be the 'Bible' for avian hybridization, with over 4000 examples. He has also extensively studied mammalian hybrids.
Furthermore, recently a team has found that the Platypus, which looks like a cross between a duck and an otter, and exhibits traits of both families, laying eggs and giving milk, has avian DNA in it's genome. It does not have DNA similar to avian DNA. It has actual genes otherwise known only from birds. Just as it looks to be, the Platypus is a bird x mammal cross. It is a hybrid of a very distant set of parent species.
There are many known naturally hybridizing species around the world, and many of these hybrids occupy stable territories between the parent populations, and have since observations began. Hybrids generally suffer reduced fertility, have a morphology that is a compromise between the parent species, and usually are the product of species relatively similar.
Many people know the mule is a hybrid, and know mules are sterile. While this is largely true, it is not completely true that all mules are sterile. Some have produced offspring, albeit rarely. Most hybrids are more fertile than mules, although some hybrids are even less fertile than mules.
There are many species whose origins are now known to be hybridization events. There are whole genus' of species that are infertile yet continue to reproduce asexually, including lizards, and not only plants. Some hybrids are partially fertile when back crossed to one or both parent species. Some species are, in fact, a range of hybrids and back crosses of broad morphological forms.
In fact, the term species is probably not really very useful, scientifically speaking, because of hybridization, which blurs the lines between species hopelessly. A more useful way to describe organisms is in terms of their DNA. A population that has a given genetic type can be termed a chromoset. Individuals that hybridize with parents of that chromoset are not members of that chromoset, because they have a different complement of genes, a different set of chromosomes.
Stabilization Theory proposed by Dr. McCarthy says that species arise through hybridization, and we have many, many examples of such hybrids today. Such species are morphologically different from the parent species right from the get go, and do not gradually evolve over time. This matches the fossil record very well.
Evolution is not monophyletelic, but polyphyletelic. Instead of species diverging from a common ancestor, species create new hybrid forms, that link two ancestries, and create a totally new form from scratch. Instead of a tree of life, branching off as species evolve from common ancestors, evolution should be represented by a kind of web, where branches are joined when new hybrids arise. According to Stabilization Theory, Darwinian evolution is not how species usually form, although it is not impossible for species to form that way.
There are just no known examples of species forming that way, and no evidence in the fossil record for it. There are many examples of hybridization forming species, and the fossil record seems to show exactly that kind of evolution. Species arise fully distinct from their parent species, persist unchanged for a while, and then go extinct. That's what the fossil record shows, and that's what Stabilization Theory proposes, with lots of living examples.
Why isn't this theory widely accepted, taught in schools, or even discussed by most biologists? The answer is the evolution of Homo sapiens.
Human evolution is a political minefield. Atheists, various religionists, and all sorts of groups have a lot of skin in the game, basing their world views on certain explanations of why we are how we are. You may not be utterly dependent on a given explanation for human origins, but you surely know people who are, and whose world views are a matter of faith, not logic or scientific study.
Some people will fight to the death rather than change their minds, their religious views are so important to them. No matter what evidence you show them, or how convincing you think it is, they are immune to it. This includes atheists. Atheism is a religion, and atheists are amongst the most strident of proselytizers. Their faith in no God is so unshakable that they will make all kinds of ridiculous statements that show no amount of reason or evidence would ever change their minds.
This is true for most religions, amongst the more faithful of their adherents. So the study of human evolution is politically dangerous, and Dr. McCarthy's theories have offended almost every type and form of religion that exists, including atheists, Muslims, Catholics, and Protestants, and almost every other religion you can think of. He has received death threats, had his funding yanked, and eventually left his post at the University of Georgia.
Why? Because H. sapiens according to Stabilization Theory is a hybrid, like all species. Dr. McCarthy examined candidate parent species and found a reasonable pair of species that explained certain unique traits H. sapiens exhibits: Pan paniscus x Sus scrofa, the chimpanzee and the pig.
I am sure you can see immediately why Dr. McCarthy not only has suffered an insane amount of harassment and abuse, violent objections and derision, as well as his hypothesis on human origins, but Stabilization Theory, tainted by the human origins hypothesis, has been smeared and derided as well.
Despite the fact that we have hundreds of known examples of species that have arisen via hybridization naturally, and are still alive today, and that the theory very well explains the fossil record, hardly anyone can stomach being the offspring of a pig and chimp, and so anything he says has to be dismissed by those whose worldviews cannot even withstand the idea of being descended from common ancestors shared with chimps.
Nonetheless, Stabilization Theory is the best explanation for evolution that exists today, and the hypothesis of human hybrid origins also best explains many human traits that are otherwise nonsensical. Dr. McCarthy does not mention one human behavioral trait that is very rare, our hypersexuality, a trait shared by only three mammals, humans, Bonobos, and Dolphins.
He says there is no need to incite any more outrage over his work. I am sure he is correct, but the subspecies of Chimpanzee known as Bonobo uses sex very much like humans do, to establish status, form social bonds, and defuse tension, as well as procreate, and I find this to be strong evidence that his hypothesis is correct.
During the Cambrian explosion, almost all known phyla, or morphologically distinct body plans, sprang almost instantly out of nothing in as few as 2 million years. Most estimates are around 10 million years. This is utterly impossible in Darwinian evolutionary theory, punctuated or not, particularly as all these phyla arose at once, not sequentially.
Prior to the Cambrian almost none of the phyla we know today existed. Some few that are known from the Pre-Cambrian are Cnidaria, Ctenophora, Annelida, Coelenterata, and perhaps Arthropoda. However there are other data than fossils, and there are claims that the divergence of vertebrates and invertebrates occurred about a billion years ago, almost twice as old as the Cambrian.
The spectacular radiation of phyla in the Cambrian is strong evidence for hybridization, as the various body plans seem to be combinations of traits or new traits. Since there are no precursors, these must have been created out of combining features of the parent species, as hybrids tend to do, and compromises between those forms producing novel intermediate forms.
Something dramatically changed life during the Cambrian, and I believe it was hybridization. As to why hybridization so suddenly and radically changed life then, and not before, it is unclear. Oddly, since that remarkable period, almost no phyla have arisen.
Certainly hybridization continues to occur, yet new phyla fail to be introduced into the fossil record except for a very few. There seems to have been a concurrence of certain unknown factors that enabled hybridization to occur between extremely divergent species which resulted in novel phyla, which wasn't happening before, and hasn't happened since.
Research continues to extend our knowledge of evolution and life deeper and further into the past. Perhaps we will be able to arrive at sound theses regarding that unique era of diversification of living forms which explains why such basic reformulations of phyla no longer occur.
I know I will be interested when someone comes up with a something as important as Stabilization Theory again.
