Many times people who are evolution deniers (creationists) argue that there is no proof of evolution. It takes thousands of years for evolution to take place and therefore it cannot be observed and proved. We have only fossils to contend with. And deniers don't accept DNA markers as proof because they cannot see it with their unaided eyes!
All of these (the list is by no means complete) convincingly supports the theory of evolution and the age of the earth:
Fossils (transitional forms, extinct species, fossilised footprints, marine fossils on mountain tops)
Superposition of geological strata
Radiometric and radiocarbon dating
Plate tectonics and continental drift
However, we have proof of micro-evolution i.e., developing drug resistance in micro-organisms is proof of micro-evolution.
But surprisingly, scientists recently observed convergent evolution before their own eyes!
Evolution is normally described as the consequence of freak mutations winding up helping a species adapt and change.
''Rapid Convergent Evolution in Wild Crickets''
- •Male crickets on two Hawaiian islands recently lost song-producing wing structures
- •Silence protects mutant males from attack by acoustically orienting parasitoids
- •Mutant wing phenotypes are distinct on each island and are linked to different loci
- •This pattern is best explained by extremely rapid convergent evolution
The earliest stages of convergent evolution are difficult to observe in the wild, limiting our understanding of the incipient genomic architecture underlying convergent phenotypes. To address this, we capitalized on a novel trait, flatwing, that arose and proliferated at the start of the 21st century in a population of field crickets (Teleogryllus oceanicus) on the Hawaiian island of Kauai. Flatwing erases sound-producing structures on male forewings. Mutant males cannot sing to attract females, but they are protected from fatal attack by an acoustically orienting parasitoid fly (Ormia ochracea). Two years later, the silent morph appeared on the neighboring island of Oahu. We tested two hypotheses for the evolutionary origin of flatwings in Hawaii: that the silent morph originated on Kauai and subsequently introgressed into Oahu and that flatwing originated independently on each island. Morphometric analysis of male wings revealed that Kauai flatwings almost completely lack typical derived structures, whereas Oahu flatwings retain noticeably more wild-type wing venation. Using standard genetic crosses, we confirmed that the mutation segregates as a single-locus, sex-linked Mendelian trait on both islands. However, genome-wide scans using RAD-seq recovered almost completely distinct markers linked with flatwing on each island. The patterns of allelic association with flatwing on either island reveal different genomic architectures consistent with the timing of two mutational events on the X chromosome. Divergent wing morphologies linked to different loci thus cause identical behavioral outcomes—silence—illustrating the power of selection to rapidly shape convergent adaptations from distinct genomic starting points.
Populations of a male cricket on different Hawaiian islands have lost their ability to chirp as a result of separate, but simultaneous, evolutionary adaptations to their wings. The changes, which allow the insects to avoid attracting a parasitic fly, occurred independently over just 20 generations and are visible to the human eye, a study reveals.
The findings could help to shed light on the earliest stages of convergent evolution — when separate groups or populations independently evolve similar adaptations in response to natural selection.
Male field crickets (Teleogryllus oceanicus) are known for their chirping sound, which is produced by scraping their wings across one another. The wings’ veins form special structures that make the vibrations that we hear as the crickets’ song. “The mechanism is like rubbing your fingernail on the file of a comb,” says study leader and evolutionary biologist Nathan Bailey of the University of St Andrews, UK.
The nightly serenades lure in females and facilitate reproduction — but unfortunately for the males in Hawaii, the chirping also attracts a deadly parasitic fly, Ormia ochracea. The fly larvae burrow into the cricket and grow inside, killing the host when they emerge a week or so later.
Both species are likely to have arrived in Hawaii at the end of the last century — the cricket from Oceania, and the fly from North America. To protect themselves from their new enemy, large numbers of male crickets on the Hawaiian island of Kauai quickly stopped chirping.
The change seems to have been caused by a mutation that altered the shape of their wings, making them incapable of producing the chirping noise. The feat was achieved over less than 20 generations, a mere evolutionary blink of an eye, and, with the crickets living just a few weeks, a very rapid process.
This evidence suggests that the mutations happened independently on both islands, making the Hawaiian silent crickets “an excellent example of convergent evolution”, says evolutionary biologist Richard Harrison of Cornell University in Ithaca, New York.
Although evidence for convergent evolution can be seen throughout the natural world, it is difficult to catch it as it happens. The study shows that superficially similar convergent solutions to attacks by parasites attracted by sound “can evolve in radically different ways”, says Tom Tregenza, an evolutionary ecologist at University of Exeter, UK. “The genome can create similar results using very different sets of genes.”
The creationists are already saying this is mere adaptation! But evolution is the change in a population over time. And these changes are beneficial for the crickets! It is a process in which the genetic structure and physical anatomy change in relation to the changes happening in the environment. This fits the 'evolution' not adaptation.
Individuals can adapt, but it takes a whole population to evolve.
Will they evolve into a new species? Wait and watch! The gene pools are separating. We can say this is earlier stages of convergent evolution. I know more observations are needed to completely mark them as new species. Now the males will have to find a new way to attract the females! I am sure they would! But this is the beginning.
A word of caution though: I think it is too early to say whether the evolution is going to be vertical or horizontal here- whether a new species is going to evolve or not. If the males adopt a different mechanism to attract the females, the females have to change or mutate too to be receptive. Then both males and females become new products of evolution. The whole scenery changes then. If some males have to chirp in order to reproduce, they will have to remain as they are and fall prey to their enemies. Natural selection will decide which type of evolution this is going to be - macro or micro.
The peppered moth case is different in the sense that the moths didn't face so much pressure as the crickets do to completely change their gene structures. The former case is just adaptation.
The moths didn't face the problem of reproduction when they had the change in colour. A simple adaptation did the trick there. Now the crickets have to think about another reproductive strategy when they stop chirping. The females have to change too to become receptive to that change. The genetic changes will become more complicated here. That is why I think this case comes under macro - level of evolution.
I agree, the changes need not be as drastic in case of crickets as we expect them to be and put them in the macro category. They need not be as small as the micro ones too. The future will tell what will happen. Let us wait and watch before coming to a conclusion.
But how wonderful it is to be able to observe this process! To fill the gaps. And have some proof!
Don't know how many more are waiting to be discovered! Creationists, watch this space!
How warp-speed evolution is transforming ecology
Darwin thought evolution was too slow to change the environment on observable timescales. Ecologists are discovering that he was wrong.
Read another such rapid story of evolution here: http://kkartlab.in/group/some-science/forum/topics/ah-another-evolu...