Scientists claim to have observed evolution happening. In 1971, they exposed 5 pairs of Italian wall lizards on island of Pod Mrcaru moved from a neighboring island Pod Kopiste in the South Adriatic Sea. They observed the spreading population in the spring and summer of 2004, 2005, and 2006 and noticed morphological changes: in head size and shape, increased bite strength and the development of new structures in the lizard’s digestive tracts; and changes in social behavior, too, while DNA analysis confirmed that the Pod Mrcaru lizards still were genetically identical to the source population. The phenotypical changes can easily be explained by adaptation to distinct environmental condition. These observations lead them to conclude they have actually observed large-scale evolution as they assume these changes are probably genetically encoded and the result of natural selection (http://www.pnas.org/content/105/12/4792.full.pdf).
But is this really evolution? I’d rather inclined to call it genetic adaptation thought I’m fully aware that most evolutionary biologists do not discriminate between genetic adaptation and evolution. The book (http://www.amazon.com/Philosophy-Biology-2nd-Dimensions/dp/0813391261/) cites the standard definition on page one “ … evolution occurs precisely when there is a change in gene frequencies found in a population.” Some other rather call it allele frequencies or inherited traits (http://en.wikipedia.org/wiki/Evolution and http://www.amazon.com/Evolution-Douglas-J-Futuyma/dp/0878931872/). What most evolutionary biologists agree upon is that evolution is not reversible. I’m not sure in this lizard example that the observed changes are not reversible. These following hypothesis adress adaptation that is completely revesible:
- Hypothesis: All observed changes in these lizards are in fact epigenetic, that appeared during ontogenesis because if distinct environmental factors. I hope the scientists ruled that out as it can be done experimentally. However the observation that DNA does not differ between lizards on these two islands rather supports this hypothesis.
- Hypothesis: The alleles encoding traits that reputedly evolved on Pod Mrcaru were actually already present in the source population but recessive or suppressed by a recessive suppressor gene. The most ancient documented example of such a phenomenon to my knowledge is from the bible. In that story a shepherd takes a herd of white sheep and by clever breeding turns them all black.
- Hypothesis: There are reversible adaptation processes to the genomic DNA itself. That we may want to call adaptational genomic DNA editing. This hypothesis, I admit, is quite hypothetical, as hypothesis often use to be. It can be deduced from fauceir theory though, and we already know phenomena that fit into the picture. These are (1) controlled changes to somatic DNA in immune cells, and (2) changes in copy number of amylase gene (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2377015/pdf/nihms-44514.pdf). Also we observe a similar phenomenon in sticklebacks’ variation in lateral plate pattern and number probably depending on predators (http://www.jstor.org/pss/4535321). Later analysis demonstrated only few loci involved (http://www.jstor.org/pss/4535321), which makes it plausible that these loci have been turned on and off by controlled mutations. Sure this is supporting evidence at most. Of course, it does not prove the hypothesis yet.
There are however two possibilities that actually evolution occurred in this Pod Mrcaru experiment. That is changes that fulfill the fauceir definition of being not reversible and entailing increased complexity, also measurable as increased adaptability.
- Hypothesis: The Pod Mrcaru underwent evolutionary changes that ensure (1) isolation from the source population, either no fertile offspring (rather unlikely as the genomic DNA is obviously the same) or other impediments to mate (possibly such impediments include body size and communication) and (2) the ability to fill an other ecological niche. The first presumption is necessary to prevent the allele pool of both types to mix again, and the second assures that both types are not competitors, so that one can substitute the other. This type of evolution would not result in a more capable lizard but a more complex biotope, so this type of evolution, also called speciation, it not as much an evolution of the lizard itself but an evolution of the biotope as a whole, an other fauceir under fauceir theory’s consideration.
- Hypothesis: The Pod Mrcaru underwent evolutionary changes itself. That is it evolved mechanisms to adapt more rapidly to environmental changes. For instance, a new transcription factor capable to effectively sense environment, then switches on and off other genes accordingly to change the phenotype in response to the prevailing factors, such as food supply. This is real evolution to the lizard as it makes it a more complex fauceir and more resistible to environmental changes, more capable. If moved back to the Pod Kopiste island, it would probably substitute the original one.
The last hypothesis is my favored, but I suppose that such a change happened millions of year ago, and all what we observed on Pod Mrcaru island is the lizard demonstrating this innate capability. Who knows, if exposed to appropriate environmental conditions, after a few generations the lizard’s phenotype will change into a dinosaur, just kidding of course.
This work by Paul Netman is licensed under a Creative Commons Attribution-Share Alike 3.0 United States License.
Fauceir theory is developed and © by Mato Nagel and available at www.fauceir.org.