The way I understand it, evolution is the natural process of random genetic mutations coupled with natural selection. In most cases, genetic data is correctly copied from cell to cell, and then from parent to offspring. But when an error occurs at any point in this process (a mutation), the result can be a benefit, a cost or neither. If the mutation doesn’t kill off the organism (e.g. offspring born with no lungs), then it is the environment that determines if it is a cost or a benefit. So if you took 2 of the exact same species and put them on different planets (or different parts of the world), the exact same mutation might help it on one planet, and kill it on another. Please correct me if any of this is wrong.
Mutations are occurring all the time. Just the fact that genetic data is transferred trillions and trillions of times tells us that there will be some mutations. Do we know what percentage of information transfer results in a mutation? Does this vary based on the type of cell or by species?
One of the classic examples of successful evolution is camouflage. There are snakes that are patterned in a manner that is similar to their surroundings. Presumably, other snakes (relatives) that didn’t evolve this camouflage were killed off by predators. Have we ever found examples of unsuccessful evolution? For example, a coral snake with zebra stripes. I understand that most of these types of examples would have been killed off immediately. But on the other hand, just the sheer number of species and mutations would suggest that some would have survived (at least temporarily) by pure accident. It suggests to me that we should see some fossilized versions of bad evolution.
The reason I ask these questions is that I’m very unprepared when I debate the religious types. These are some questions that I haven’t had an appropriate answer to. And as many of you know, with people like these, any inability to answer even the most tangential questions seems to automatically render the whole theory garbage. Though it only seems to work in one direction.
Oh, yes, plenty of times. A cousin of mine was born with muscular distrophy, and based on family history, the doctors decided that the mutation which led to it was probably original to him (or at most, to his mother). It’s conceivable that there’s some environment in which that would be an advantage, but here and now, it’s a disadvantage. So that’s an “unsuccessful evolution”. Somehow, I don’t think this is what you were trying to ask (the answer seems too obvious), but I can’t think of any other way to interpret it.
Mutations are very common. I remember reading a study that said that the average person had about 90 (roughly) mutations. I also remember reading something from talk origins saying that the average person has something like 64 mutations. Most of them are obviously neutral.
I’d think that mutation rate/frequency would vary by the species though.
During WWII, the Army took over a huge section of woods and farmland near Seneca Lake in upstate New York for a munitions base. They built an unclimbable fence around the entire property, trapping a herd of deer that quietly co-existed with the Army for 60 years.
However, these deer had a recessive gene that gave them snowy white coats all over. Because of the inbreeding, there is now a herd of several hundred white deer still living on the unused site.
Pure whiteness is not a survival adaptation: predators would pick them out too easily. But isolation of populations and the subsequent inbreeding is possibly the commonest thread in evolution. It’s the same mechanism behind Darwin’s finches, the ones in the Galapagos Island. It’s the reason that Finns have some of the rarest conditions in the world, as the mountains broke up clans into separate groupings. It’s why Australia is full of marsupials that exist nowhere in the world. For that matter, it’s the same reason why New Guinea has 1000 languages, though that’s cultural but not genetic. The mechanism is essentially identical. All these gene combinations (and word combinations) come originally from mutation but are amplified by inbreeding.
So the entire world is an example of random mutations giving birth to non-adaptive conditions, some of which by fluke of environment do happen to survive to act as living examples.
While mutations add information, most variation comes not from mutation but from the mixing of characteristics as a result of sex. For the snake example, if there was a range of skin patterns, those that serve as the best camouflage would be selected for. Remember also that this is a statistical process - not all snakes without the camouflage will die, and not all with it will live. Since we find such a tiny percentage of all the animals who ever lived fossilized, it is not at all strange that we’d not see many examples of a “bad” mutation.
Most mutations are neutral, either not affecting the animal or being in DNA that is turned off.
You’re right about the planets - though we can see the same thing when a species gets split and winds up in two different environments right here on Earth.
An excellent book describing genetic mutations in humans, and what we can learn from them is: Mutants: On Genetic Variety and the Human Body. This is an exceedingly well-written book and treats a subject that has great potential for becoming little more than a freak-show with great compassion and sympathy.
And that fascinating subject is most commonly called “Island Biogeography.” An excellent work on this subject is David Quammen’s The Song of the Dodo. Another book on the subject, probably the first and still one of the best, is Alfred Russell Wallace’s, Island Life.
Mutations typically vary by group. Why, exactly, this is the case is not fully known right now. As an example of the numbers, though, the average mammalian genome mutation rate has been calculated at 2.2x10[sup]-9[/sup] / base pair / year.
I doubt there are many cases of “unsuccessful evolution”. However, there are a good many cases of “successful” not-obviously-beneficial-or-even-downright-detrimental mutations. Natural selection is not a guarantee of survival or death for any given individual; it’s a statistical process that translates to “over time, those with the more beneficial mutations will have a greater than average chance to pass on their genes, while those with detrimental ones have a lower than average chance of doing so”. So a macro-mutation like a zerba-colored snake in the forest is not likely to occur. But a slight change in striping pattern may occur, and even if it does make the snake a bit more detectable, that individual could still beat the odds and survive to mate. However, unless that individual’s lineage continues to beat the odds, it is unlikely to persist in the population for many generations.
A paper in Nature a while back detailed a computer simulation in which seemingly detrimental mutations can appear and act as a “jumping off” point whereby an advantageous trait can eventually evolve. So, it is possible that a detrimental mutation can occur as an intermediate in the evolution of a given trait, and that the detrimental mutation can be further built upon to eventually serve as an adaptation, instead of the more typical “each stage is beneficial or, at worst, neutral” action.
Actually the probability of a creature winding up as a fossil of any kind is remote. The pobability that the fossil will be found is also pretty slim. Ergo, there is no reason to be surprised or to have to account for the lack of such a fossil
And, fossils are mainly skeletons and most mutations aren’t skeletal. Even so, there is a pretty complete line of descent in the fossil record for many species, such as thehorse.
As Struan noted, no. Extinction is more complicated than simply weeding out “inferior” species. Often, the “killing blow” is delivered too swiftly to allow the population to evolve to the new conditions (whatever they may be). In most cases, extinction is more attributable to bad luck than bad genes.
UncleBeer, you’re starting to remind me of my father when I was a kid. I’d ask him a question, and he’d respond by answering it…and then giving me a book to read. He’d wait about a week and then start asking me questions about the book, which more-often-than-not I hadn’t read. I eventually stopped asking him questions. It’s tough to be inquisitive AND lazy. But I suppose it keeps this website in business.
Well, obviously I ain’t your father. We know that because I didn’t even attempt to actually answer your question. Which leads us to another question - Who’s lazier, you or me?
“Shit” is just environmental change on meth. A meteor that wipes out a species quickly is no less part of the enviroment than a lethal virus doing it gradually and both are completely random.
Here is an example of a fossil with a mutation that was non-adaptive. There is no sense arguing with evolution-deniers, however it might be fun to preface everything with God. “God invented natural selection. He is so powerful that he didn’t create each species individually like you or I would, instead he put a process in place that allowed the first single celled creatures to evolve into humans that could build cathedrals”. When they argue, you can say “why do you deny the majesty of God”? Have fun with it.
Correct. The usefulness of a mutation depends on the environment in which it occurs. An animal camouflaged for the arctic isn’t going to do as well in the rain forest.
There are plenty of examples of environmentally neutral mutations suddenly becoming an advantage or disadvantage.
Dodo bird: had no instinct to run from predators. This was environmentally neutral because there weren’t any predators on their isolated island. This is similar to the kakapo, which is not yet (knock on wood) extinct.
Peppered moth: light-colored moth that slept on light-colored lichen on trees for camouflage. When the Industrial Revolution began to blacken the bark of the light-colored trees with coal soot, their advantage turned into a distinct disadvantage.
It’s tough to be inquisitive AND lazy. But I suppose it keeps this website in business.