Microevolution, broadly defined, is the inevitable small-scale changes in allele frequencies in a population within the same species. Under this broad definition, this change in overall allele frequencies occurs with every birth or death of a member of the species. In other words, some generations of people might be taller than the last or shorter than the last based on the number of individuals who happen to have the "tall" gene. Microevolution does not involve changing from one kind to another, and it does not create new kinds.
Evolutionists have argued that the distinction between microevolution and macroevolution is arbitrary because it is the same process.
Microevolution in Bacteria
Microevolution is the process by which bacteria may develop resistance to antibiotics. We regularly use antibiotics to stop bacterial infections. When a colony of bacteria is exposed to an antibiotic, the bacteria are likely to die if they do not have genes that produce molecules to inhibit the action of the antibiotic. If the survivors reproduce, the colony will contain mostly bacteria that have inherited resistance genes. A second application of the same antibiotic will not affect them.
Genes to resist various antibiotics are natural for bacteria to produce because the many species of bacteria war with each other for more space using these chemicals on each other. In order to protect itself a given species of bacteria would at least have genes for resistance to the particular antibiotic it produces. Resistance genes can also be produced by random mutation, usually through mistakes in copying the DNA during cell division. Furthermore, bacteria can pass genes for antibiotic resistance between strains and even between species.
Because antibiotics have been used so widely in medicine, there is increasing concern about developing strains of bacteria that can acquire multiple resistances to most of the antibiotics we use. High compliance with infection control measures and a prudent and more restrictive use of antibiotics are the key measures to prevent epidemics based on bacteria with multiresistance.
If the world is as old as is commonly claimed, we should see animals today evolving at a rate consistent with this, over thousands and millions of years. That is why it is shocking for the scientific community that the accumulating evidence shows instead that Microevolution occurs over decades, rather than thousands and millions of years. David Skelly of Yale University has observed that the evolutionary rates are far faster than those presumed by evolutionary theory:
|“||Ecology is being transformed by the recognition that ecological and evolutionary timescales are not easily differentiated. A 1999 review of evolutionary rates by Andrew Hendry and Mike Kinnison (The pace of modern life: measuring rates of contemporary microevolution. Evolution 53:1637-1653) provided the striking conclusion that rates of contemporary evolution are much faster than generally appreciated... Our work reveals that a number of traits including critical thermal maximum, embryonic development rate, and thermal preference behavior all show variation consistent with local adaptation that occurs on the scale of decades and tens of meters. These findings offer a startlingly different picture of interactions between organisms and their environment prompting us to rethink, in larger sense, how we should conceive of ecological assemblages.||”|
Australia's 'Toxic Toad'
In one of the most widely publicized cases of unexpected rapid Microevolution, Australian Cane Toads defied predictions based on evolutionary theory by experts about how they would react after being introduced to Australia. Within decades they evolved longer legs and heat tolerance, running amok and causing havoc for the wildlife; and instituting a national catastrophe for the continent.
|“||The evolutionary processes spawned by the cane toad invasion have occurred in a span of just 70 years. This adds to evidence from the past two decades that populations can adapt quickly when selection pressure is strong. 'We're taught evolution occurs over these very, very long time frames. But in systems like these, it's incredibly fast,' Shine, the study co-author, said.||”|
|“||'All of a sudden in the last 10 years it changes,' said Skelly. 'They're moving into areas where the physical environment is not like anything in their native range.' That implies that the cane toads have evolved more tolerance for the hotter climates they are now encountering. This is on top of the discovery last year that the toads at the forefront of the invasion had evolved longer legs than those in the interior of their range. The ability of animals to evolve so quickly needs to be factored into invasions, or the dangers of invasive species will likely be underestimated, argue Skelly and his colleagues Mark Urban, Ben Phillips and Richard Shine in an article in the March 28 issue of the Proceedings of the Royal Society-B.||”|
According to the assumptions of evolutionary theory, if evolution always went at the rate that we see today, there should be 160 times more differences between humans and apes. So rather than assume 'the present is the key to the past', scientists then decided that evolutionary rates today have accelerated for some reason.
|“||If humans had always evolved at this rate, the difference between modern humans and chimps should be 160 times greater than it really is. 'We realized we must be in a transient [phase], that evolution hasn't been going this fast for long in our species,' Harpending said. 'And so we wondered why.'||”|
|“||'I was raised with the belief that modern humans showed up 40,000 to 50,000 years ago and haven't changed,' explained Henry C. Harpending, an anthropologist at the University of Utah. 'The opposite seems to be true.'... If evolution had been proceeding steadily at the current rate since humans and chimps separated 6 million years ago there should be 160 times more differences than the researchers found. That indicates that human evolution had been slower in the distant past, Harpending explained.||”|
Italian Wall Lizards
In 1971, scientists introduced 5 pairs of Italian Wall Lizards to a small island off the coast of Croatia. However, the Croatian War of Independence prevented the scientists from returning to the island for more than 30 years. When the war ended, tourism finally began again in 2004, allowing them to return. The researchers were unsure if the lizards would still be alive. Instead, they found the island swarming with lizards, which genetic testing showed to be descendants of their original 5. The new lizards had wiped out native lizard populations by evolving cecal valves, muscles between the large and small intestines, with which to digest native vegetation, an expanded gut structure, as well as a harder bite.
|“||Italian wall lizards introduced to a tiny island off the coast of Croatia are evolving in ways that would normally take millions of years to play out, new research shows. In just a few decades the 5-inch-long (13-centimeter-long) lizards have developed a completely new gut structure, larger heads, and a harder bite, researchers say... Such physical transformation in just 30 lizard generations takes evolution to a whole new level, Irschick said. It would be akin to humans evolving and growing a new appendix in several hundred years, he said. 'That's unparalleled. What's most important is how fast this is,' he said.||”|
Contrary to theoretical predictions based on evolutionary theory, genomes for the Angiosperm Silene (a flowering plant) evolved far more rapidly than was expected, as reported in the January 2012 issue of PLoS Biology. Researchers are now trying to find an explanation for why such rapid Microevolution is occurring, and a new model that will avoid such surprises in the future.
|“||Contrary to theoretical predictions, these genomes have experienced a massive proliferation of noncoding content... The evolution of mutation rate, genome size, and chromosome structure can therefore be extremely rapid and interrelated in ways not predicted by current evolutionary theories... We discuss the implications of the unprecedented mitochondrial genome diversity found within Silene and possible alternative explanations for the rapid genome evolution in this genus.||”|
A 2009 study observed that rodents evolve at "unprecedented rates" given climate change and population growth, and that rapid evolutionary change in rodents has been occurring for over a century. The article also notes research on rapid Micrevolution has previously been "infrequently documented", but that despite this, more and more evidence is cropping up for it.
|“||Our results indicate that over the last 100+ years, rapid morphological change in rodents has occurred quite frequently, and that these changes have taken place on the mainland as well as on islands. Our results also suggest that these changes may be driven, at least in part, by human population growth and climate change.||”|
Microevolution in Creation Science
Whilst some creationists agree with the concept of microevolution, but call it adaptation, they argue that there is a large difference between microevolution and macroevolution. However, evolutionary scientists do not make any real distinction between the two, and leading creationists argue that using the terms "microevolution" and "macroevolution" obscures the real distinction, that being between the unobserved information-generating mutations that evolution requires and information-destroying mutations that are observed.
- Skelly, David K. "Rapid Evolution." Yale University. School of Forestry & Environmental Studies.
- Roach, John (2006, February 15). "Toxic Toads Evolve Longer Legs, Study Says." National Geographic.
- O'Hanlon, Larry (2007, April 2). "Toxic Toads Evolving Quickly." DiscoveryNews.
- Roach, John (2007, December 11). "Human Evolution Speeding Up." National Geographic.
- Schmid, Randolph E. (2007, December 10). "Researchers: Human Evolution Speeding Up." The Washington Post.
- Johnson, Kimberly (2008, April 21). "Lizards Rapidly Evolve After Introduction to Island." National Geographic.
- Sloan, D.B., Alverson, A.J., Chuckalovcak, J.P., et. al. (2012, January). "Rapid Evolution of Enormous, Multichromosomal Genomes in Flowering Plant Mitochondria with Exceptionally High Mutation Rates." In PLoS Biology. Public Library of Science.
- Pergams ORW, Lawler JJ (2009, April 21). "Recent and Widespread Rapid Morphological Change in Rodents." PLoS ONE 4(7): e6452. doi:10.1371/journal.pone.0006452.
- AAAS press release 
- Arguments we think creationists should NOT use (Creation Ministries International).