EvC Forum: Species/Kinds (for Peg...and others)

Hi jasonlang, nice post, but I have some nits:

1. Phenotypic change does not necessarily indicate any evolution at all, let along hyperevolution. All species have pre-evolved adaptability to changes in conditions. Consider the great increase in height / longevity of the Japanese population since WW2, which nobody would claim to be evolution but which would score high on the "darwins" (14 yo Japanese boys now are as heavy as adults at the end of WW2)
2. Where short term genetic adaptation occurs it is almost %100 through competition between variations in the gene pool in response to changes in the environment.

You are correct that this is phenotypic change, but it is not a "pre-evolved adaptability" or a genetic (genotype) change. The increase in height and weight occurs in the individuals across the board, because it is due to better nutrition and better medical care, especially pre-natal and early formative years care. In essence the ecology has changed to improve the health and well-being of the individuals. This is\was observed in every third world country where better nutrition and medical care was brought to bear.

Nor is this due to adaptability, as the ecology does not require increase in height or weight for survival or breeding, so this change is not an adaptation to a restriction of the environment. Rather it is a relatively selection neutral development.

3. Paleontologists use average size of specimens when determining long term evolution trends. You wouldn't claim that because you found a small adult T-Rex fossil and a much larger one from 1 year later that T-Rex suddenly evolved bigger, because chance in plays a part in the individual life of each animal or group.

And they include the population variation as part of the equation. Take Pelycodus as an example:

A Smooth Fossil Transition: Pelycodus

quote:

he numbers down the left hand side indicate the depth (in feet) at which each group of fossils was found. As is usual in geology, the diagram gives the data for the deepest (oldest) fossils at the bottom, and the upper (youngest) fossils at the top. The diagram covers about five million years.

The numbers across the bottom are a measure of body size. Each horizontal line shows the range of sizes that were found at that depth. The dark part of each line shows the average value, and the standard deviation around the average.

The dashed lines show the overall trend. The species at the bottom is Pelycodus ralstoni, but at the top we find two species, Notharctus nunienus and Notharctus venticolus. The two species later became even more distinct, and the descendants of nunienus are now labeled as genus Smilodectes instead of genus Notharctus.

As you look from bottom to top, you will see that each group has some overlap with what came before. There are no major breaks or sudden jumps. And the form of the creatures was changing steadily.

And they also consider sexual dimorphism and maturity of the specimens.

In the above diagram we see a clear trend in size of the whole population, and it is on a time scale that would likely find your example of Japanese youth just a blip.

4. The predator is also adapting to the guppies. At first, the abundant new food source benefits each predator roughly equally (boosting predator survival all round, little competitive pressure), but as the predator population maxes out and the guppies grow bigger to avoid being eaten, those predators able to eat the larger prey will be selected for. As this continues, the advantage of being a large guppy will eventually diminish and the guppies may shift back towards producing a high quantity of young and being smaller again.

Individual cases of faster than average evolution are not a surprise, nor is it a challenge to the Theory of Evolution. It is a common creationist misunderstanding that evolution claims change must be slow, when in fact evolution is a response mechanism, and so the rate of change is driven by the degree of selection pressure. Where selection pressure is high and continuous, then evolution will occur in every generation - which is extraordinarily fast compared to geological time - and either the change keeps up with the pressure or the species goes extinct.

Sexual selection is an example of continuous selection pressure, and where there is fisherian run-away sexual selection it can drive phenotypic and genetic change very rapidly of succeeding generations.

We also see instances where a species is introduced to a new environment\ecology, with the ability to infiltrate and commandeer that environment\ecology quite rapidly:

Differential Dispersal Of Introduced Species - An Aspect of Punctuated Equilibrium

quote:
(2) European Starling

Page not found | RAINIER AUDUBON SOCIETY

In the early 1890's, the Acclimation Society of North America released 50 pairs of Starlings into New York's Central Park as part of a project to introduce every bird ever mentioned in a Shakespeare play. Only 50 years later their populations had spread across the continent, competing for nesting sites with our native birds.

From only 50 starlings to continent wide in less than 50 years.

And there are other examples - dogs and rabbits in Australia, dogs and cats in the Hawaiian Islands, etc etc etc.

Rapid speciation and dispersal of new diversity can also occur following an extinction event for species able to take advantage of the opportunity and potential loss of predators.

Geology Dept article 3

"What we've found suggests that the rate of speciation increases dramatically in a biological vacuum," Parker said. "After the Cretaceous extinction, the few surviving foram species began rapidly propagating into new species, and for the first time we're able to see just how this happens, and how fast."

As foram survivors rush to occupy their new habitats, they seem to start experimenting will all sorts of body shapes, trying to find something stable, something that will work, Arnold said. Once a population in a given habitat develops a shape or other characteristic that stands up to the environment, suddenly the organisms begin to coalesce around what becomes a standardized form, the signature of a new species.

As the available niches begin to fill up with these new creatures, the speciation rate begins to slow down, and pressure from competition between species appears to bear down in earnest. The extinction rate then rises accordingly.

So, far from being a problem, rapid evolution is expected to vary in rates from slow to generation by generation fast.

Enjoy.

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