finch

Finch Varieties in New Guinea Undercut Iconic Galápagos Finch Story

Look at these photos of colorful finches found in New Guinea via Boston University. What amazing variability we see: coloration patterns so different, a taxonomist would readily categorize them into different species. Now read this from Michael Sorenson, who with Katie Stryjewski catalogued 301 finch species in New Guinea:

Sorenson discovered that the entire group of New Guinea finch species was more genetically similar than is typical for the birds within a single African finch species. [Emphasis added.]

It may take a re-reading of that sentence for its significance to sink in. Ever since Darwin, evolutionists have made a fuss about the 13 or so species of finches on the Galápagos Islands, which vary only slightly by millimeter-size differences in their beaks. Numerous books, papers, and seminars have been held about “Darwin’s Finches” as demonstrations of natural selection and the origin of species. Peter and Rosemary Grant have spent decades deciphering their significance. We were told that those small variations took millions of years for natural selection to create.

And now, all of a sudden, we have an even greater population of finches in another island community that tells a whopping different story. Does Sorenson’s research advance the Darwin finch story, or fly in its face?

Michael Sorenson, a professor of biology, explains that the birds are an evolutionary anomaly: Despite their striking coloration differences, all 11 species are extremely closely related, suggesting that they evolved quickly and recently (evolutionarily speaking), even faster than the famous Darwin’s finches of the Galapagos.

This points to an “extraordinarily recent and rapid radiation” occurring over tens or hundreds of thousands of years (compared to millions of years for most bird species).

Something is going on here that could change the whole evolutionary spiel. If you can get morevariability in less time by non-selection processes, then Darwin’s finch icons may be going out of style. Biologists should flock to New Guinea for better insight into biological change.

But how and why did these close relatives end up looking so different? And how did they evolve so quickly into different species? Biologists have long wondered exactly how new species form, but generally assume that new genetic mutations account for the changes in form and function that ultimately make each species unique. However, that may not always be the case, and studying unusual groups like the finches of New Guinea helps biologists better understand other ways new species emerge, revealing more about evolution as a whole.

They have just abandoned the classical neo-Darwinian mutation/selection mechanism to explain these finch varieties. By extension, they could repudiate it for the Galápagos finches as well, seeing as how those finches show even less variability. So what is their new explanation? First, Sorenson feels it necessary to pledge allegiance to evolution, lest he become suspect:

Speciation is the process by which the incredible diversity of life on earth came into being — including humans,” Sorenson says. “It is not only one of the most fundamental processes in evolutionary biology, but is central to understanding the history of life on earth.”

Sorenson just saluted the talking points of Darwinism: evolution is a fact, it accounts for the origin of species, and nothing in biology makes sense except in the light of evolution. No creationism to see here. No intelligent design. Having blown the all-clear whistle, he can say what he really thinks.

First, he and Stryjewski establish their credentials as empirical scientists. They showed impressive rigor in bird collection and genetic sequencing.

To understand how this extraordinary group of finches evolved, Katie Stryjewski… collected birds throughout New Guinea and carefully preserved blood, feather, and tissue samples, with Sorenson joining her on the last of four trips. Then Stryjewski used genome sequencing to peer deep inside the birds’ genetic codes.

Photos of some of Stryjewski’s carefully written data cards and notebooks leave no doubt. Sorenson, too, having sampled many finches in natural history museums, polishes his credentials:

My career has been a somewhat less-than-coherent series of studies on out-of-the-ordinary examples of behavior and evolution in birds,” he says. “The unifying theme, however, is an interest in understanding not only the evolution of new species, but also the diversity of behavior and morphology observed in different species.”

If he wanted out out-of-the-ordinary examples of evolution in birds, he clearly has that on his hands. As he said, these New Guinea finches, despite their diverse color patterns, have more genetic similarity than individuals within a single African finch species! Some birds from overlapping regions maintain distinct plumage patterns.

Sorenson was intrigued. “Which genes are involved? And how many genes does it take to build this species versus that species?” he says. “The profound genetic similarity of these species provided the perfect opportunity to answer these questions.”

Their field work was impressive: trips to remote regions by river, living with villagers, setting up mist nets, taking samples and making taxidermy specimens, and keeping diligent notes. It’s like the grand voyages of discovery, using some of the old methods of Darwin himself on the Beagle. But this time, the two had a new tool to add to the mix: genetic sequencing. And therein lays a new emerging picture. Comparing genes of different finches revealed a new mode of speciation:

Stryjewski and Sorenson identified about 20 genes that differed among finch species, half a dozen of which are known to control coloration in other organisms, including humans. Different combinations of genes were mixed and matched among species, “as opposed to new mutations cropping up,”Stryjewski says. “Each version of a gene is like a different little thing you could put on a Mr. Potato Head doll, and each bird is collecting a different set of them, and so they all end up looking different.”

A startling conclusion! Very different from the typical evolutionary story. The new scenario shows finches shuffling existing traits, as if playing Mr. Potato Head together.

Sorenson adds that “the birds’ genes likely interact with each other in complex ways, making the plumage that results from a particular combination of genes something more than the sum of the parts.” Sorenson thinks that occasional interbreeding between species that live in the same area … likely how different versions of genes moved from population to population over time.

The result of this mixing of already-present genetic information? Profound differences in appearance. Look at the 11 species of finches shown in their paper in Nature Ecology & Evolution: the vastly different color patterns are astonishing. There are beak size differences, too.

Darren Irwin, a zoologist at the University of British Columbia, praises the research for its “elegant analysis of a particularly interesting recent and rapid avian radiation.” He adds that scientists usually think of new species as arising from a single species splitting into two, but “this study provides a great example of how new forms arise in part through mixing genes from other populations.”

If Sorenson’s goal was “to advance general understanding of how evolution works,” he has advanced it in a very un-Darwinian direction! In the paper, Sorenson and Stryjewski call it “collateral evolution” and compare it to the Galápagos case:

The precise history of allelic variants at individual outlier loci is also difficult to reconstruct, but differential selection on retained ancestral polymorphisms and/or lateral transfer of adaptive alleles via introgression must have been involved in generating the mosaic patterns we observed. These processes comprise two forms of ‘collateral evolution’, defined as the parallel evolution of ancestral genetic variants in independent lineages and recognized as an important mechanism for convergent evolution. In Darwin’s finches, for example, ancestral alleles at two loci are associated with changes in bill morphology across multiple species. Likewise in the munias [New Guinea finches] ancestral alleles may underlie convergent components of each species’ unique phenotype, but we suggest that collateral evolution also contributed to phenotypic diversification by generating new combinations of alleles across a relatively small set of potentially interacting colour genes and other functionally relevant loci. The role of ancestral variation and collateral evolution in producing phenotypic novelty and diversity may be under-appreciated.

The variations do not require mutations culled by natural selection over millions of years. They can arise quickly by recombining already-existing genes in complex ways. Intelligent design theory can handle that. In addition, because of epistasis, pleiotropy and recombination, and possibly epigenetics, even more heritable variations on the theme can be generated from the information bank. Variations would tend to radiate outward, but not upward.

To be clear, the authors affirm neo-Darwinism: “Natural selection and recombination combine to produce heterogeneous patterns of genomic divergence between nascent and recently evolved species,” they say. But their own work does not require mutation and selection. All these colorful birds came about by recombining genes in different ways — genes that already existed, and still exist in humans.

Our results suggest that differential selection on ancestral genetic variation and lateral transfer of alleles via introgression have contributed to the phenotypic diversification of the Lonchura munias by generating unique combinations of alleles across a relatively small set of phenotypically relevant genes.

These scientists did not observe “ancestral genetic variation.” They observed different combinations of genes. Might this shed light on other cases of so-called “adaptive radiation” like Caribbean anole lizards, South American Heliconius butterflies, and even human beings? After all, we humans inhabit vastly different environments around the world, many of them overlapping. No biologist would dare classify us as different “species” based on hair color, or skin color, or body build, which can differ dramatically. We share pre-existing genes by lateral gene transfer, too. Often groups tend to isolate themselves by social preferences — not by mutation and selection. The differences in Homo sapiens are arguably as pronounced as those in the finch study. What’s Darwinism got to do with it? We’re all just playing Mr. Potato Head and having fun. Even Neanderthals played the game, because we all have Neanderthal genes.

Despite the authors’ pledge of allegiance to Darwinian evolution, the new finch study puts a very different spin on biological change. “Collateral evolution” looks more like a bush than a tree. The bush grows out from the center, as different combinations of existing genes create variations, but Mr. Potato Head does not evolve into something completely different. The authors had very little to say about mutation and natural selection in their paper: certainly nothing about its ability to create novelty from scratch.

Nobody would claim that “collateral evolution” can account for all the variability in the living world, but the new work on finches opens up possibilities for explaining a great deal of variability within groups, apart from neo-Darwinian mechanisms. It certainly casts doubt on neo-Darwinism as a progressive, creative force leading to a great branching tree of common ancestry. As Darwin stands over there scratching his head, those Galápagos finches don’t look so good anymore as icons of evolution. And neither do peppered moths, horses, or hominids.

By the way, in his update to the Darwin’s finches story in Zombie Science, pp. 67-70, Jonathan Wells makes a similar case for the varieties on the Galápagos. He cites evidence of extensive interbreeding and hybridization between the supposed 13 “species” of finches, noting that it is “far from obvious why we should consider them separate species at all.”

Photo credit: Katie Stryjewski, via Boston University.

Source: Evolution News

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