As pointed out later, it depends on the proteins produced. However, in one of the most famous and documented cases of evolution by natural selection, the mutation was immediately apparent. The first notice of a dark morph in the Peppered moth (Biston betularia) was in 1848. Until then all observed moths had been of the light-speckled variety. From then until 1895 the percentage of dark morphs increased until it had reached 95% in polluted areas. As pollution was reduced during the last half of the 20th century, the number of dark morphs also declined.
I believe that evolutionary biologist L. Harrison Matthews wrote that the peppered moth case was simple natural selection, but not evolution in action. Am I missing something here ?
"The [peppered moth] experiments beautifully demonstrate natural selection—or survival of the fittest—in action, but they do not show evolution in progress; for however the populations may alter in their content of light, intermediate or dark forms, all the moths remain, from beginning to end, Biston betularia."
—*L. Harrison Matthews, "Introduction," to Charles Darwin's Origin of the Species (1971 edition), p. xi
Thanks for the answer, although I had that understanding of evolution, its always good to explain it as you did just to make sure.
Although I would have thought 'evolution in action' would have been an addition of information in the peppered moth population. Harrisons seems to be saying that the moth population just alternated from light to dark to light again, which isn't really new information, if those color were already there ...
Yeah we better not use the term information, or it will not end.
Let's just say that it is not a new trait in the population.
Coyote: depends on what you mean by evolution. If you mean descent with modification sure you don't need new information. But if you mean bacteria-to-elephant evolution, then at some point you will need new information. (or rather new traits)
What I wanted to say is this. If you show me a population of pinches, who's beeks change in size and shape depending on the environment and the food they have access to, and say this is descent with modification, then I will readily approve with you.
But if, after having shown me this, you tell me that such a mechanism, extrapolated to vast amounts of time, could turn a pinch into let's say, a horse, then I will not agree with you. I will simply say that ''maybe we are actually seeing a small part of the process of the pinch becoming a horse, but then again, maybe we are not, and are simply watching a characteristic of the population vary back and forth according to selective pressure.
If you want to use the former (descent with modification) to prove the latter (dinosaurs are the ancestors of birds, modern apes and humans have a common ancestor, etc.) you will need much more than that.
This is why it would be interesting to discuss the Lenski experiment, since when I read the article back in 2007, it was actually the very first time that I said to myself: maybe they finally have it, maybe they do have a recorded example of a new trait evolving in a population. Which is what is needed to go from the descent with modification to vast scale evolution of bacterias to microbiologists.
''If you want to use the former (descent with modification) to justify the possibility of the latter (dinosaurs are the ancestors of birds, modern apes and humans have a common ancestor, etc.) you will need much more than that.''
I acknowledge it is not the same thing. But my original idea was this one.
You'll have to give me a little chance people, although I consider myself good in english, it is not my first language and where I live you never get the chance to even speak english other than 2 hours a week in school. Stuff like this will happen, me using the wrong vocabulary doesn't mean I'm trying to pull a strawman (nor that I'm dumb, mind you ;) )
Ok so why do I have these as examples of evolution in my biology book then ?
Neither would I, any one familiar with biology or an experts in the field. So you are in good company.
Then you would have thought wrong. Evolution does not require an addition of information. There are, of course, several mechanisms of evolution that do, in fact add information to the genome of a population. It is also true that the addition of information to the genome of a population is, by definition, evolution. However, evolution can also happen when information in the genome of a population is reduced. You see, at the most basic level, evolution is a change in the allele frequencies in a population over generations. That is what happened (twice) in the case of the peppered moths. And it happened because of natural selection (one of the mechanisms of evolution).
I mean, they talk for about 10-15 pages about the happening of life in ancient-earth oceans, then about how bacterias evolved into fish, to ampibians, etc. from dinosaurs to birds, from australopithecus to humans, etc.
And then they arrive with the proofs of the theory of evolution, and I have variation of the color of peppered moth in the population, and the beaks of finches on the galapagos island, plus some story about big and small fishes in amazone rivers, similar to the peppered moth. I was like, what the heck ? I have no doubt that this kind of situation is not only in my biology book, but in many (if not most) others.
There could be an effort done to distinguish the evolution: simple descent with modification and the theory of evolution: from bacteria to bacteriologist. As you have said, simple examples of descent with modification can't really be used to justify the possibility of the later. I much more like examples such as Huntard's; of nylon digestion in bacteria, an argument I knew of but hadn't really investigated and so it will be very pleasant to do here BTW.
Ok. How about genetics, fossils and similar morphology...?
We will be discussing these subjects I hope, but in genetics alone, a good read would be ''genetic entropy ...'' by Dr. John Sanford. He gives a couple dozens citations from population geneticists which are extremely revealing of the many problems genetics and mutations pose to the theory of evolution. This maybe seems counter-intuitive, but I can tell you his book is one of the must bullet-proof I have seen on both sides. (and I read quite a lot)
Maybe I was unclear: I am advocating that these two concepts SHOULD be more distinguished in evolutionary literature. I'm not saying they are not, but I'm saying it is not uncommon to have an example of natural selection in action to justify the possibility of dinosaur to birds.
We are saying exactly the same thing here.
A look through the reviews of it suggests that he has a theoretical argument that what we observe can't happen and what we never observe must. It reminds me of the (apocryphal) story of the scientists who claimed to have proved that bees can't fly.
It also appears to be standard creationist rubbish, although maybe I'm doing him a disservice --- maybe they got it from him.
I don't know which review you read, but his argumentation is not solely theoretical. it is based on population genetics, and on the cost of selection. It is nothing I have ever encountered in creationist litterature.
What he advances is this: mutations are accumulating in the genome, reducing slowly, but steadily, the overall fitness of the population. The vast majority of mutations are deletirious, with again most of them being near-neutral, and so are in Kimura's 'no selection zone' in his graphic of mutation distributions. It has no relevance with 'what we are seeing can't happen', he is right on par with the population geneticists.
So your biology book provides the example of finches evolving into horses? Interesting. I suggest you use it for heating purposes the next cold winter.
Now this is entirely reasonable, so maybe you shouldn't burn your biology book after all. A finch evolving into a horse is not the same as what you say here. Birds aren't even mammals.
Thanks for the assurances, but you just revealed that you think a finch evolving into a horse is a valid example of evolution, so the evidence would suggest that despite your voluminous reading you lack the understanding of biology necessary for assessing the validity of what you read. About Sanford Wikipedia says:
Technically, what prevents mutations+natural selection to have birds become mammals in the theory of evolution? Nothing of course. I wan't saying it happened in the past, I was saying that according to evolution, it could happen in the future.
Now if you are saying otherwise (which I don't think you are, BTW), then you'll have to say why.
When looking at the chimp and human genome, how much of a difference is there? Depends on the comparison. Of the DNA stretches that humans and chimps share the sequence is about 98% identical. That is, out of every 50 bases there is one point mutation. But what about the whole genome? Overtime genomes can gain and lose DNA also known as insertions and deletions (indels for short). When these are part of the comparison there is an overall similarity of 95%.
So the question that must be posed to those critical of evolution is this. Of the differences between humans and chimps, which CAN NOT be produced by the observed mechanisms of mutation? I know of none. For me, these simple premises lead to an unavoidable conclusion. There is nothing stopping evolution from evolving humans and chimps from a common ancestor.
I'll ask you another question, similar to yours. Of the differences between humans and chimps, whichow can it be produced by the observed mechanisms of mutation in the span of 6 million years ?
Man and chimp differ by at least 150 million nucleotides, representing at least 40 million hypothetical mutations. So if man evolved from a chimp-like creature, then during that process there were at least 20 million mutations fixed within the human lineage (the other 20 million being in the chimp lineage). This means you have to fix over 3 mutations per year in the population (considering the divergence 6 millions years ago). Even considering generations of 1 year, this is, at best, unrealistic. (human generations are currently 20 years)
Haldane had calculated in 1957, that it takes, on average, 300 generations to select a single mutation to fixation in a population. Although I agree there has been revisions of his calculations in the past fifty years, there are no actual numbers that come even close to the fixation rates needed. All the fixations not done by selection have to be done by genetic drift, which is way slower then selection.
So to answer your question, even if we assume that mutations can create the different information between chimps and humans, even the evolutionnary time scale is not long enough to allow for such massive changes, unless you assume impossible fixation rates.
Prokaryotic genetics is very different then eukaryotic genetic. The no selection zone of mutations is quasi-inexistent, thus why bacteria populations adapt rapidly to new environment, but remain overall static in that they stay the same specie. E.Coli has remained E.Coli from its discovery in 1885 up until now.
That's a good way to wish away inconvenient results. Anything which breeds fast enough to definitively prove you wrong is deemed not to suffer from these magical mutations which cause extinction but aren't selected against. And anything that doesn't, has them ... even though you have no empirical evidence to support this claim.
Since you claim that the dividing line is between prokaryotes and eukaryotes, how do you feel about ... yeast? That's eukaryotic. What's the excuse this time?
How convenient you took away the phrase that would solve the puzzle ;). I didn't mean a clear line between prokaryotes and eukaryotes. Its about the no selection zone as I mentioned. It is quasi-inexistant due to low noise, and so the phenotype reflects much, much, much more the genotype of the bacteria. Which allows the fixation of new beneficial mutations to be very fast, and the eliminations of delitirious mutations much easier.
As for that second question, let's just say that if the bacteria hasn't changed from its original description at the moment of its discovery (and the further more precise descriptions that came afterwards) then it is still the same species.
I'm gone to sleep now, we can talk about the lenski experiment tomorrow.