I frequently hear as a criticism of evolution that it can’t be observed in a controlled environment. Is this true?
I’m guessing there are about a thousand other people typing even as I am and someone, somewhere is linking to something very much like this, which is a PBS study guide discussing only one simple case where evolution absoluely can be observed directly in a laboratory, in a controlled enviroment.
Here’s a bunch of 'em: http://www.talkorigins.org/faqs/faq-speciation.html .
It’s good reading for other reasons, too – it explains how very loose and artificial our definition of “species” is, for example.
Is it considered a scientific fact that humans and other apes share a common ancestor?
There’s no such thing as a “scientific fact.” Science is only about assigning likelihoods and probabilities; anything might be shown false by further evidence. (This disclaimer, critical to an understanding of science and therefore pointed out whenever anyone asks, is NOT equivalent to “we can’t know anything, and therefore all explanations are equally valid,” as Creationists usually interpret it.)
That said, the evidence for it is overwhelming; the probability that we do not share ANY common ancestor would invalidate everything we know about biology, and is vanishingly small. The chance that we’ve incorrectly identified the MOST RECENT common ancestor is higher, and still a matter of some debate.
Yes, using the term “fact” loosely, as we have to when dealing with issues of science. It’s certainly long been accepted by the vast majority (possibly even everyone) working in the field of evolution, including all the people viewed as authoritative by their peers.
Put it another way, there is zero good evidence otherwise (unless you’re the sort of person who counts the Bible as evidence), and plenty, plenty of evidence for the current view of the lineage of apes, including DNA analysis, comparative morphology and fossil evidence.
The only people who are disputing the evidence are those who base their beliefs on literal interpretation of religious texts. These tend to be the same people who believe things like “the Earth was created in 4004BC”, and with them I will have no truck.
There is absolutely no doubt whatsoever that all known life forms share a common ancestor, and that furthermore the common ancestor of humans and other apes is very recent.
I have to wonder if the frequent criticism you hear about the observability of evolution is that we can’t see the common ancestor of apes and humans. Or possibly that we can’t observe one species evolving into another in a lab.
Do you have any links to sites that make these or other criticisms?
Wouldn’t this also be true of things like continental drift and planetary motion?
No, that is absolutly not true. It’s just that some people switch definitions to suit their purpose. What would be called evolution on long timescales in the wild is called breeding when it happens under controlled conditions and in the timespans amenable to direct observations in the laboratory. The poorly controlled selection pressures directing survival in the wild in the laboratory are replaced by artificial selection criteria, and the rate of change can be accelerated by chemical mutagens or radiation. Techniques called “directed evolution” and “in-vitro evolution” are routinely used to generate novel biomolecules and adapt microbial strains for biotechnological applications.
Microorganisms have been successfully evolved to metabolize substances their parental strains could metabolize very poorly or not at all, allowing them to potentially populate new evolutionary niches if they were to be released into the wild, plants have been evolved to grow on heavy metal contaminated soils for bioremediation, and from the evolution of a worm towards longvity a lot has been learned about the mechanisms of ageing.
Critics of evolution call this microevolution and deny evidence of speciation under laboratory conditions. But here the real problem is the definition of that separates one species from another. If you analyze the evolutionary changes on a generation to generation base, you normally cannot assign generation n to species A and generation n+1 to species B. It is like looking at the spectrum of light: Unless you are suffering from some form of color blindness, you dont’t have any problems pointing at the red, orange, yellow, green, blue, or purple region of the spectrum. But going through the spectrum in very tiny steps, looking at small changes in wavelength, can you point out at what exact wavelength the change from yellow to green occurs?
A single mutational event such as a chromosomal translocation can lead to reproductive separation without any change in the appearance or behavior of an organism. Another single mutational event, inactivating a control gene, can cause a major phenotypical change, such as a fly growing legs where its parent had its antennae. But a serious scientist will not call either of these mutational events speciation, but will refer to the mutated offspring as separat strains or breeds of the original species. There is no simple and precise scientific definition of “species” which, if strictly applied, would not contradict the current placement of many organisms in the catalog of biological species.