The word 'theory' has many meanings, including: systematically organized knowledge; abstract reasoning; a speculative idea or plan; or a systematic statement of principles. Scientific theories are based on both observations of the natural world and assumptions about the natural world. They are always subject to change in view of new and confirmed observations.
This textbook discusses evolution, a controversial theory some scientists present as a scientific explanation for the origin of living things. No one was present when life first appeared on earth. Therefore, any statement about life's origins should be considered a theory.
Evolution refers to the unproven belief that random, undirected forces produced living things. There are many topics with unanswered questions about the origin of life which are not mentioned in your textbook, including: the sudden appearance of the major groups of animals in the fossil record (known as the Cambrian Explosion); the lack of new major groups of other living things appearing in the fossil record; the lack of transitional forms of major groups of plants and animals in the fossil record; and the complete and complex set of instructions for building a living body possessed by all living things.
Study hard and keep an open mind.
Now to anyone with any knowledge on the topic, it's easy to see why such a statement is incredibly misleading; doing a disservice to both science, and to the students. For a topic like evolution where there is controversy in the public arena, it's hard to explain why public controversy is not the same as academic controversy. But what if a similarly worded and toned sticker would be used on other textbooks. Take for example a book on world war 2:
The word 'theory' has many meanings, including: systematically organized knowledge; abstract reasoning; a speculative idea or plan; or a systematic statement of principles. Historical theories are based on both observations of the artefacts and assumptions about unrecorded events. They are always subject to change in view of new and confirmed observations.
This textbook discusses the holocaust, a controversial theory some historians present as a historical explanation for the genocide of the Jewish people. No one who was killed in the gas chambers survived to tell the tale. Therefore, any statement about the holocaust should be considered prone to error.
The holocaust refers to the unproven belief that there was a systematic and deliberate genocide committed by the Nazis on Jews. There are many topics with unanswered questions about the events that transpired in the concentration camp which are not mentioned in your textbook, including: the coercion Nazi officers post-WW2 into giving confessions; the lack of evidence of any explicit plan to commit such an atrocity; the lack of evidence that there was any bad treatment of the Jews by the Germans; and that there are many pieces of evidence that point to a Zionist conspiracy.
Study hard and keep an open mind.
It's important to remember that there are more historians who reject the holocaust than there are scientists who reject evolution. Once the argument is moved to another field where there's the same amount of academic controversy (i.e. essentially none) and no public controversy, the deceptiveness of the argument becomes apparent.
3 comments:
Kel,
I do try to get here more often, but tend to get distracted. Today you benefit from Pharyngula being down!
An analogy I use when presented with some sort of wildly improbable event (ultimate 747, for example) is to agree - yes, an extremely improbable event is practically impossible - say, rolling all sixes on a billion six-sided dice. Then I explain that evolution isn't one roll of a billion dice to get all sixes; it's the roll of all the dice, keeping all the sixes that are rolled, and then rolling the remaining dice again. You keep those sixes, and roll the rest again. Repeat unto infinity - eventually you're going to get all sixes. Yes, it's going to take lot of time, but that's one of the joys of evolution: no-one defending it claims it happens quickly.
I do have a question about evolution that you might be able to answer - or link to somewhere the question's been asked and answered before - since I'm a bit tentative about asking it anywhere else 'cause it might be a dumb question.
Anyway, say in a mutation occurs - e.g. a scorpion with extra-strong toxin in its stinger. This happens to one scorpion at time, correct? So this first scorpion uses it's super-sting for defence (or offence, or both) and survives to breed.
Is the idea that that one scorpion breeds enough that, eventually, it has so many offspring (over several generations) that the gene for that mutation is carried by its great-great (to the nth power) grandchildren, who breed with each other and make it occur more frequently?
Or does another scorpion mutate in the same way and eventually the offspring of the two meet up and create a race of super-scorpions (so to speak)?
Does what I'm asking make sense? What I'd really like to find is a step-by-step hypothetical (or, since we know evolution happens, an example) of a particular genetic development. I've looked, but I'm guessing it was never in the right place, 'cause I'm still at a loss to explain that aspect of evolution.
Can you help a brother out?
Cheers,
Wowbagger
The short answer is I don't know.
The long answer is that I could imagine that both could occur in nature, though I'd expect single mutations to be the way things work. For instance blue eyes are the result of a single mutation. So over time there's no reason that a single mutation over successive generations should be passed on.
There's an interesting example of something similar happening in the real world, it was highlighted on the PBS Nova series Evolution. There's a newt that secretes a toxin described as one of the most deadly in the world, the reason for this is that there is a garter snake that preys on the newt that can handle the toxin. So there was an evolutionary arms race between the two creatures.
Of course that doesn't answer your question, it's just a cool example that does show that such variation can happen. As for whether it's one mutation or a series of multiple mutations that all converge, I don't know.
Just on a simply evolutionary perspective, each generation would have a variety of mutations in each individual. The mutations that are advantageous will have a higher chance of being passed down than the members of the generation that aren't passed down. So if there are a few different mutations that are all advantageous, then those ones should all survive to be handed down. So there would be an accumulation of advantageous mutations over enough time.
So individually an advantageous mutation would take several generations for it to be passed through a population. But honestly that's the best I can deduce from the literature I read, and it comes back to the short answer to the question.
Kel,
Fair enough - it doesn't come as a surprise there's not an 'obvious' answer to it; otherwise one of us would have seen it explained before.
The more I think about it, the more unlikely it would be for anyone to necessarily know which of the two ways, since the mutations are only observed afterwards, rather than as they progress.
But you've reminded me that we're all carrying variations on our our parents' genes in us, and so we're all, technically, 'rolls of the dice' for mutation - that's something I need to remember.
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