I’m afraid the topic for this month’s effort is a little disconcerting for your ol’ buddy Tom. Not because of the science involved — oh no, absolutely not. Indeed, it is powerful and meaningful science.
So what has made me hesitant? Wait for it …
So why would I even bring up this subject in the first place? Well, it’s Darwin Week and Feb. 12 is Darwin Day, in recognition of the birthday of Charles Darwin (1809-1882), the British naturalist best remembered for his work “The Origin of Species” and considered to be the father of modern evolutionary theory. Scientists and teachers use this time to increase public awareness and education of the subject.
No other topic in science incites as much reaction and emotion. Yet many are confused or misguided as to what evolution and its divisions really are and are not. First, some basic terms:
FACT AND THEORY
This is a problem found throughout the whole of science: The difference between how “fact” and “theory” are used in science contrasted to ordinary public discourse.
According to the National Academy of Sciences (NAS), a fact is “an observation that has been repeatedly confirmed and, for all practical purposes, is accepted as true.”
“Facts are based on our current understanding of the world, which in turn is based on current hypotheses that have been tested and supported by evidence,” said Natasha Vanderhoff, assistant professor of biology and marine science at Jacksonville University.
OK. That seems simple enough.
Ah, but the word “theory” opens an entirely different can of worms; in everyday vernacular, the word implies “guess.”
But it actually has a completely different meaning in science. According to the NAS, a scientific theory is “a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences and tested hypotheses.”
“A theory is a series of well-tested and supported hypotheses, and while hypotheses may be disproven over time, they usually help to solidify theories that grow, but do not necessarily at their core, change,” Vanderhoff said.
And as new evidence is discovered, theories may be modified or refined.
“To everyday folk, a fact is a constant and a theory is a bit wishy-washy — [and] it’s just the opposite!” she added.
SO WHAT IS EVOLUTION?
In the broadest sense, evolution simply means change over time. Galaxies, planets, economies, politics, relationships and even values are just some examples of things that evolve.
Biological evolution is the change of the gene pool of a population over time — that is, the change in the properties of a population of organisms that transcends the lifetime of a single member.
Nowhere in the definition, though, do we find the words “progress,” “ape,” “Darwin,” “natural selection,” or “come from.” Note, too, that evolution does not address the biochemical origin of life, which is called abiogenesis.
There are two types of evolution, first described by Russian entomologist Yuri Filipchenko, who was working to reconcile Mendelian genetics with evolution in the early 1900s:
■ Microevolution: small differences of characteristics within a population, or changes below the level of species, such as populations of insects becoming immune to a pesticide or bacteria becoming resistant to an antibiotic.
■ Macroevolution: evolutionary change at or above the level of species. This can involve the splitting of a species into two (cladogenesis), or the change of a species into another (anagenesis). Amphibians evolving into reptiles or reptiles evolving into birds are two examples.
Evidence exists that supports both.
We should also be familiar with the term mutation, which is best thought of as changes in the genetic material carried by chromosomes. It occurs spontaneously as copies of genes are made for growth and reproduction. Mutations may occur by chance, as a molecule here or there gets misplaced, or could be the result of external factors, such as radiation or a harsh chemical environment.
Evolution could not occur without such changes.
Tom Webber is the director of the Bryan-Gooding Planetarium/Alexander Brest Space Theater at the Museum of Science & History.