Birds and Micro-Evolution

I devoted a substantial part of Genesis and Genes to a discussion of macro-evolution and micro-evolution. The difference is crucial. Micro-evolutionary changes are intra-species events; they are common and uncontroversial. Macro-evolutionary changes are needed to drive real biological innovation – they supposedly lead to new organs and new body plans. Macro-evolutionary changes are the stuff of common descent. If all life on Earth today arose from one or a few one-celled organisms, there had to have been untold millions of macro-evolutionary changes along the way.

The earliest references to the terms micro- and macro-evolution that I could find were made by one of the architects of Neo-Darwinism, Theodosius Dobzhansky. As I wrote,

In 1937, Dobzhansky noted that there was no hard evidence to connect small-scale changes within existing species (which he called microevolution) to the origin of new species and fundamentally-new structures (an eye or a wing where there hadn’t been one before) and body plans that are recorded in the fossil record (which he called macroevolution).[1]

 According to Dobzhansky,

There is no way toward an understanding of the mechanisms of macroevolutionary changes, which require time on a geological scale, other than through a full comprehension of the microevolutionary processes observable within the span of a human lifetime. For this reason we are compelled at the present level of knowledge reluctantly to put a sign of equality between the mechanisms of macro- and microevolution, and proceeding on this assumption, to push our investigations as far ahead as this working hypothesis will permit.

Dobzhansky clearly acknowledged that it is nothing but an assumption and a working hypothesis that the accumulation of micro-evolutionary changes can account for macro-evolution. This has been controversial right from the beginning. In 1940, Berkeley geneticist Richard Goldschmidt argued that “the facts of microevolution do not suffice for an understanding of macroevolution.”[2] Goldschmidt added that “Microevolution does not lead beyond the confines of the species, and the typical products of microevolution, the geographic races, are not incipient species.”[3] At the other end of the century, evolutionary biologists Scott Gilbert, John Opitz and Rudolf Raff wrote in 1996 that:[4]

Genetics might be adequate for explaining microevolution, but microevolutionary changes in gene frequency were not seen as able to turn a reptile into a mammal or to convert a fish into an amphibian. Microevolution looks at adaptations that concern the survival of the fittest, not the arrival of the fittest.

 Gilbert et. al concluded that, “The origin of species – Darwin’s problem – remains unsolved.”

Unfortunately, most members of the public are not aware of the enormous difference between micro- and macro-evolution. This ignorance is exploited by the evolution establishment. Numerous examples of micro-evolution are provided in newspapers, documentaries, and websites, and are then conflated with macro-evolution to foster the impression that macro-evolution has been established.

I discussed a number of examples of this phenomenon in Genesis and Genes. Readers will recall the less-than-thrilling discovery, discussed in Nature’s “evolutionary gems” online resource, regarding small birds in Southern England. Nature promised readers that they would see “marked evolutionary differentiation” at “small spatial and temporal scales.” The journal informs its readers that over a span of about 35 years, the birds known as great tits from the eastern part of the Wytham woodland saw a decrease in adult body size that amounted to a net average change of about 1 gram (less than 10 percent of total body mass). Fledgling birds likewise saw a small change in body mass. Birds in the northern part of the wood did not experience such a change.[5] Needless to say, this is hardly evidence for the grandiose claims of evolutionary biology regarding the ability of natural selection acting on random mutations to produce birds in the first place.

Here are two more recent examples of this phenomenon, both from the sphere of avian life.

A rather prosaic discovery was reported last month in Current Biology[6] and was summarised in Science Now:[7]

Cliff swallows that build nests that dangle precariously from highway overpasses have a lower chance of becoming roadkill than in years past thanks to a shorter wingspan that lets them dodge oncoming traffic. That’s the conclusion of a new study based on 3 decades of data collected on one population of the birds. The results suggest that shorter wingspan has been selected for over this time period because of the evolutionary pressure put on the population by cars.

It seems clear that shorter wings give birds better manoeuvrability:

“Probably the most important effect of a shorter wing is that it allows the birds to turn more quickly,” says [ecologist] Charles Brown [of the University of Tulsa in Oklahoma, who conducted the new study with wife Mary Bomberger Brown, an ornithologist at the University of Nebraska, Lincoln.] Previous studies on the dynamics of flight have illustrated the benefits of short wings for birds that perform many pivots and rolls during flying and shown that shorter wings also may allow the birds to take off faster from the ground, he adds.

So what’s the significance of this data-acquisition exercise?

“This is a clear example of how you can observe natural selection over short time periods,” says Brown. “Over 30 years, you can see these birds being selected for their ability to avoid cars.”

But how significant are these changes in the grand scheme of things? The report tells us that,

When the researchers analyzed the average wing length of the living birds in the population, they discovered that it had become shorter over time, from 111 millimeters in 1982 to the 106 millimeter average in 2012. The data suggested to the Browns that roadkill deaths were a major force driving this selection. Birds with longer wings would be more likely to be killed by vehicles and less likely to reproduce…

So, over 30 years, the average length of the swallows’ wings became shorter by about 5 mm, or 4.5%. Must we, um, swallow the claim that this example of natural selection, together with non-teleological mutations, is convincing evidence for the origin of birds, as well as all life-forms on earth?

***

Nature recently reported on research published in Science. The study in question was led by University of Utah biologist Michael Shapiro and offers “insight into the genetics of both ‘fancy’ domestic breeds and plain street pigeons and supports their common origin from the wild rock dove (Columba livia).”[8] The report begins with some background:

Humans have shaped the domestic pigeon into hundreds of breeds of various shapes, colours and attributes — a diversity that captivated Charles Darwin, who even conducted breeding experiments on his own pigeons. Now, a number of domestic and feral pigeon genomes have been sequenced for the first time, giving scientists a resource for studying the genetics of how these traits evolved.

 Here is what the research involved:

 The Utah team… sequenced a complete ‘reference’ genome from a breed called the Danish tumbler. The researchers also sequenced the genomes of 36 different fancy breeds and of two feral birds from different regions of the US.

 And the results:

 The study fills in knowledge about the relationships between breeds, many of which are centuries old with origins in the Middle East. Darwin argued that all domestic pigeon breeds descended from the wild rock dove. Shapiro says this study puts data behind that argument, as all the breeds sequenced are more similar genetically to one another than to another, closely related, species of pigeon, C. rupestris. It also found that street pigeons are genetically similar to racing homing pigeons, which frequently escape into the wild.

 So the wild rock dove is ancestral to many varieties of pigeons today. Now, the rock dove is just the rock pigeon, also known as the common or garden pigeon – the kind that soils your patio. So the claim being made here is that pigeons are descended from pigeons.

 But the humdrum nature of the research is obscured by the electric title of the report: Pigeon DNA proves Darwin right. Yeah, right; it also proves right every common peasant in Darwin’s time who knew that you could breed cows, dogs, cats, tulips and hundreds of other organisms and obtain modest results. These results always demonstrate micro-evolution: a slightly faster dog, a new breed of cow, a slightly brighter tulip.

 Darwin called his book On the Origin of Species. Neither before its publication nor thereafter has anyone been able to discover or demonstrate genuine macro-evolutionary changes. As I put it in Genesis and Genes,

But there is no reason at all to believe, at the outset, that there must be a seamless progression from micro to macro. If you have seen people walking in New York and you know that people have walked on the Moon, that doesn’t justify the conclusion that it must be possible to walk from New York to the Moon. Small processes – walking around your home, in our analogy – cannot necessarily be extrapolated to big processes – like walking in space. This notion is expressed in Dobzhansky’s reluctant admission that, as an assumption and a working hypothesis, biologists equate microevolution and macroevolution. It is something for which there is no logical imperative.

 ***

Related Posts:

An Interview with Lynn Margulis:

https://torahexplorer.com/2013/02/25/an-interview-with-lynn-margulis/

More on Margulis:

https://torahexplorer.com/2013/02/26/more-on-margulis/

 

References:

[1] Theodosius Dobzhansky, Genetics and the Origin of Species, 1937. Reprinted by Columbia University Press, 1982, page 12.

[2] Richard Goldschmidt, The Material Basis of Evolution, Yale University Press, 1940, page 8.

[3] Ibid. page 396.

[4] Scott F. Gilbert, John M. Opitz and Rudolf A. Raff, Resynthesizing Evolutionary and Developmental Biology, Developmental Biology 173 (1996): 357-372.

[5] See Dany Garant, Loeske E.B. Kruuk, Teddy A. Wilkin, Robin H. McCleery & Ben C. Sheldon, “Evolution driven by differential dispersal within a wild bird population,” Nature 433:60-65 (January 6, 2005), at: http://www.nature.com/nature/journal/v433/n7021/abs/nature03051.html

[6] You can read the summary here:

http://www.cell.com/current-biology/retrieve/pii/S0960982213001942

Retrieved 7th April 2013.

[7] See http://news.sciencemag.org/sciencenow/2013/03/evolution-via-roadkill.html

Retrieved 7th April 2013.

[8] See http://www.nature.com/news/pigeon-dna-proves-darwin-right-1.12334

Retrieved 5th April 2013.

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2 Responses to “Birds and Micro-Evolution”

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  2. The Limits of Variability | Torah Explorer Says:

    […] https://torahexplorer.com/2013/04/07/birds-and-micro-evolution/ […]

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