A branching pattern of variation was central to Darwin's concept of speciation. As one population of organisms follows one trajectory, another population may spin off in a different direction. When they are sufficiently far apart, they are considered to be separate species. The Galapagos finches have been regarded as exemplars of Darwinian transformation, even leading to the claim that one newly developed population is "behaving as a separate species". However, the most recent study, from one of the smaller islands (Floreana), concludes that the most likely cause of the disappearance of one of these species is hybridization.
"The authors suggest that hybridization may have been responsible for the disappearance of the large tree finch from Floreana, and that it may now be causing the remaining two species to fuse into one: speciation in reverse." (p.179)
Small Tree Finch (C. parvulus) from Floreana, about 4 years old. (Credit: Jeremy Robertson, source here)
Until recently, three species of tree finch were known from Floreana Island. Morphological differences noted were limited to body size and beak dimensions. Their names are the small tree finch, the medium tree finch, and the large tree finch. They are found living together in several other Galapagos islands. Now Kleindorfer and colleagues report that the large tree finch has disappeared from Floreana. The remaining two species are affected by hybridization.
"The analyses also revealed that individuals that do not fit into either population show intermediate characteristics, suggesting that they are hybrids. Consistent with the hypothesis of ongoing hybridization on the island, the authors observed females of the morphologically larger group (the medium tree finch) pairing with males of the smaller group, and they identified 15% of yearling males in 2010 as hybrids." (p.170)
Most of the researchers appear to think that their studies are probing the essence of speciation, and are providing the empirical evidence that supports the Darwinist claim that natural selection acting on inheritable variation is the key to understanding the origin of species. Peter and Rosemary Grant say that these studies are "Uniquely valuable in showing how speciation is done" (p.179). Kleindorfer et al. say that research programmes over "the past 2 decades have transformed our understanding of the ecological context of processes that underpin speciation" (p.325). With specific reference to the new findings, they write:
"The results presented here go to the heart of evolutionary biology: by what criteria do we denote species, and by what criteria do new species form or collapse? Here we present evidence that three sympatric species of Darwin's tree finches in the 1900s have collapsed, under conditions of hybridization, into two species by the 2000s. The proportion of yearling hybrid birds increased from 0% in 2005 to 14.6% in 2010, indicating a potential for elevated hybrid fitness in this system. [. . .] There is widespread agreement that the benefits of hybridization include increased genetic variance that facilitates novel evolutionary trajectories in changing environments." (p.334)
Whilst the new research is a useful contribution to knowledge, the results do not go to "the heart of evolutionary biology". The reason is that the important questions to do with diversity in the living world relate to the origin of biological information. What factors and processes are relevant to building novelty and complexity? The finches of Floreana Island are distinguished by very minor morphological differences, and the observed changes tell us nothing about the origin of new biological information.
Please can we have some realism from researchers adhering to the Darwinian paradigm. In the main, their research findings cast light on ecology but they are failing to touch the real challenges facing evolutionary biology. This assessment of their work is now appearing in mainstream peer-reviewed literature and in articles written by influential scientists. Here is a comment from Professor John Dupre, who is Director of the ESRC Center for Genomics in Society, University of Exeter.
"Further destabilizing evolutionary theory is the growing realization that many factors, not just the genome, determine an individual organism's development. Ironically, as the discovery of DNA's structure - initially lauded as the final act in the triumph of the new synthesis - led to a better understanding of genomes' functioning, it ended up weakening belief in their unique role in directing biological development. Those who long deplored the omission of development from evolutionary models - a decades-old critique made under the scientific banner of evolutionary developmental biology ("evo-devo") - together with the insistence that organisms' development draws on a wide variety of resources, have been vindicated.
"Recent developments in molecular biology have put the final nail in the coffin of traditional genetic determinism. For example, epigenetics - the study of heritable modifications of the genome that do not involve alterations to the genetic code - is on the rise. And the many kinds of small RNA molecules are increasingly recognized as forming a regulatory layer above the genome.
"Beyond undermining the gene-centered theories of evolution that have dominated public consciousness for several decades, these developments call for new philosophical frameworks. Traditional reductionist views of science, with their focus on "bottom-up" mechanisms, do not suffice in the quest to understand top-down and circular causality and a world of nested processes." (Source here. Related comments are here)
Of the greatest urgency is attention to educational textbooks. For too long, the Darwinists have maintained a hegemony that resists all critiques of their arguments. Typically, they present any questioning of their interpretation of the evidence as religiously motivated and anti-science. For the good of science, this situation has to change.
Species Collapse via Hybridization in Darwin's Tree Finches
Sonia Kleindorfer, Jody A. O'Connor, Rachael Y. Dudaniec, Steven A. Myers, Jeremy Robertson, and Frank J. Sulloway
The American Naturalist, Vol. 183, No. 3, March 2014, 325-341.
Abstract: Species hybridization can lead to fitness costs, species collapse, and novel evolutionary trajectories in changing environments. Hybridization is predicted to be more common when environmental conditions change rapidly. Here, we test patterns of hybridization in three sympatric tree finch species (small tree finch Camarhynchus parvulus, medium tree finch Camarhynchus pauper, and large tree finch: Camarhynchus psittacula) that are currently recognized on Floreana Island, Galapagos Archipelago. Genetic analysis of microsatellite data from contemporary samples showed two genetic populations and one hybrid cluster in both 2005 and 2010; hybrid individuals were derived from genetic population 1 (small morph) and genetic population 2 (large morph). Females of the large and rare species were more likely to pair with males of the small common species. Finch populations differed in morphology in 1852?1906 compared with 2005/2010. An unsupervised clustering method showed (a) support for three morphological clusters in the historical tree finch sample (1852?1906), which is consistent with current species recognition; (b) support for two or three morphological clusters in 2005 with some (19%) hybridization; and (c) support for just two morphological clusters in 2010 with frequent (41%) hybridization. We discuss these findings in relation to species demarcations of Camarhynchus tree finches on Floreana Island.
Peter R. Grant & B. Rosemary Grant
Nature, 507, 178-179 (13 March 2014) | doi:10.1038/507178b
Hybridization can cause two species to fuse into a single population. New observations suggest that two species of Darwin's finches are hybridizing on a Galapagos island, and that a third one has disappeared through interbreeding.
What Can You Do About Cosmos? Support the Summer Seminar on Intelligent Design in the Natural Sciences, of Course
At ENV, there will be more to say about Seth MacFarlane's revival of the Carl Sagan vehicle for scientific materialism after we've seen it. In the meantime, you may wish to have access to the antidote handy before grappling with the ailment itself.
For that, you couldn't do better than Illustra Media's series of stunning video documentaries on the theme of intelligent design in cosmology and biology. Most of these are actually viewable immediately as Amazon instant videos. The single most relevant film is The Privileged Planet, but don't forget The Case for a Creator, Darwin's Dilemma, Unlocking the Mystery of Life, Flight and Metamorphosis. Find them on the Illustra website or, on Amazon.
In an Evolution News & Views...In case you had any uncertainty about the upcoming 13-part Cosmos series, a revival of the Carl Sagan franchise, executive producer Seth MacFarlane has Darwin skeptics and alternatives to Darwinian evolution very much in his crosshairs. This is a major and costly project, though Fox won't say how costly - so it's flattering in a way. In an interview in the Los Angeles Times, MacFarlane says:
We've had a resurgence of creationism and intelligent design quote-unquote theory. There's been a real vacuum when it comes to science education. The nice thing about this show is that I think that it does what the original "Cosmos" did and presents it in such a flashy, entertaining way that, as Carl Sagan put it in 1980, even people who have no interest in science will watch just because it's a spectacle. People who watched the original "Cosmos" will sit down and watch with their kids.