I still don't get how evolution is random?

Question

the change in our genetic component is mainly driven by mutation, a random process that produces the good and the bad.
natural selection filters the bad and keeps the good.

but if you look at some cases like the evolution of sea creatures or drug-resisting bacteria...it's like they realized that in order to survive a specific trait must be acquired and the genetic sequence changed accordingly...
where did I go wrong? what am I missing?

P.S. I'm not religious, just new to evolution and trying to understand :)

Answer 1

The real answer is that's it's not really random. It is the result of many natural processes.



Drug resistant bacteria is one of the easier examples to simplify. Remember, when anything reproduces, it is not a perfect copy. Sexual reproduction adds a bunch of new reasons that we aren't perfect copies of our parents, but when you're talking about bacteria, the easiest way to think of it is that they're pretty good at duplicating themselves, but there are always a few tiny errors.



For the most part they're negligible, and many don't really have any noticeable effect. With millions and millions of bacteria per host, and then unthinkable numbers throughout the entire range of bacteria that might be treated using a certain drug, it becomes pretty likely that some will have their genes changed in such a way that the drug in question no longer harms them.



Once that happens, when the host carrying that small number of bacteria receives a drug, suddenly they're the only ones left, and they're free to become the dominant strain. Once that person spreads the infection to another person, you've suddenly got a drug resistant strain on the loose.



That's a fairly dramatic example of natural selection in action, but it demonstrates how new traits can appear naturally.



Evolution does not work by new traits magically appearing when they're necessary. If that's how it worked, evolution would have happened MUCH, MUCH faster. You should think of it not as a steady march of progress, but as an increase in the number of different variations on life there are. It's the slow, gradual separation of species.



There are many different factors that influence evolution, so it's kind of difficult to briefly summarize how it works without getting really confusing. I'd recommend starting with the Wikipedia article on evolution, at http://en.wikipedia.org/wiki/Evolution , and if you can, read The Greatest Show on Earth by Richard Dawkins. He goes into a lot of detail about how evolution happens. If you're sincerely interested in biology, and you're just starting out, it's an excellent read.

Answer 2

If you're not religious then you should have no problem understanding and accepting the facts of evolution.



Let me take the bacteria one as an example.



Let's assume that an antibiotic is used to attack the bacteria, let's assume that the bacteria have no way of knowing what's going to happen, that they don't 'realise' anything at all. They will all be different though, though their genomes might be short compared to ours there will still be a lot of variety. Imagine one type, say 5% have a gene which allows them to resist a certain amount of the drug.



After a few days, most of the other bacteria will be dead, let's assume the person doesn't finish their course of antibiotics - they feel better so 'what's the point?' they think to themselves. Well which bacteria are left? The drug resistant ones, none of them knew what was happening or what was going to happen but the ones with the resistance survived. Now the drug stops and the pressure is off. The bacteria thrive once again, this time the progenitors of the new generations of bacteria are all descendants of the drug resistant type. Again there is variety, some may have more resistance to the drug, many like their parent bacteria will have some resistance and some offspring will have even more resistance to it.



This is how drug resistant strains of bacteria get started. People not finishing courses of antibiotics, or antibiotics being given when they aren't strictly needed.



Though sometimes it seems like an animal 'knows' they don't - the ones least suited to the new environment die and the ones best suited survive and multiply. Mutation is random - selection is not.



Lot's of good places to learn more. Here's a selection:



Books:

‘The Origin of Species’ by Charles Darwin

‘The Variety of Life’ by Colin Tudge

‘The Ancestor’s Tale’ by Richard Dawkins

‘Almost a Whale’ by Steven Jones

‘Evolution’ by Mark Ridley

‘Evolution: An Introduction’ by Stephen Stearns and Rolf Hoekstra



Web:

http://www.talkorigins.org/

http://en.wikipedia.org/wiki/Evolution

http://www.pbs.org/wgbh/evolution/

http://www.livescience.com/evolution/



Kind Regards.

Answer 3

@secretsauce has it right.



Stop to think about it. If you have a bacterial infection, you don't have just one bacterium; your infection will consist of millions of bacteria. And you will not be the only one with that infection. Numerous other people will have the same bacterial infection, each with millions of bacteria.



Those bacteria will also have random mutations. Given the trillions of bacteria that must exist throughout all of the infections, there will likely be millions of random mutations. Most mutations are actually neutral, but some have the potential of being beneficial and some are detrimental. The bacterial with detrimental mutations will likely not survive. Beneficial mutations are beneficial with regard to the environment. If a few of the mutations are beneficial in dealing with an antibiotic that is being given to all of the people with the infection, those bacteria will be more likely to survive.



So out of all of the bacteria that have infected numerous people, a few of those bacteria will survive the antibiotics. Moreover, over time, additional mutations will likely provide even greater resistance to the antibiotic.



So there is no need for the bacteria to realize they need the trait. Because of the sheer numbers of bacteria, the odds are that a few will have a beneficial mutation that will help them to survive the antibiotic. Those will reproduce, infect other people, and so a new strain of antibiotic resistant bacteria will come on the scene.



Added:



And you can ignore what @rocket man says. He doesn't know squat about evolution, how it works, or the evidence for it.

Answer 4

Evolution is NOT random.



Mutations are random.



But evolution is more than just random mutations.



Evolution also involves natural selection, which is NOT random. There is nothing random about the fact that the fastest lions catch the most antelopes, and therefore live longer and produce more offspring. That is a fact of nature, just as NON-RANDOM as the fact that objects under the effect of the non-random force of gravity, will fall downwards, never upwards.



To pick the example of drug-resistant bacteria. In any population of millions of bacteria in your body, there are tens of thousands of tiny mutations. Most of those mutations will have no effect at all on the resistance to the antibiotics ... some will make the bacterium less resistant ... but a few of those tens of thousands of mutations may confer some extra resistance to the drugs. THOSE are the bacteria that will live a little longer, and produce more copies of themselves. The result ... the surviving population is more drug-resistant than before.



So again, the *mutations* are random. The fact that living in a toxic environment *selects* some mutations over others is NON-RANDOM.



At no point to the bacteria "realize" that they need to produce a certain mutation.



(Kudos to you for genuinely trying to understand this stuff.)

Answer 5

1. First, throw out those 'value' terms like bad and good. They confuse the issue, because they come preloaded with a bunch of asuumptions we've attached to them.

2. Then, discard any idea that any organism "realizes" that it needs something to survive better. They don't. It's not necessary.

3. And finally, chuck out the idea that evolution is random. It isn't - it's always driven in a certain direction by the selective forces that act on the organism (even if that direction is subject to change without warning).

The basic idea is this: Things come in a range of varieties, right? Big. little, different colors, different shapes, whatever. Those things that have offspring pass on their genes to the next generation, and those that have more offspring increase the relative amount of their genes in the population. OK, now if some variety of a particular thing has an advantage over the others (maybe it catches more food; maybe the females find it sexier; maybe it breeds for a longer period or its offspring survive to adulthood better, etc., etc.), then after a while the population of that thing will look mostly like that variety. Now introduce some change - perhaps a mutation that (in a freak one-in-a-billion-or-so chance) turns out to be helpful; or perhaps a change in the environment that takes away the advantage from the first variety and gives it to a different variety of that thing. Anyway, now this different variety has the edge, and starts producing relatively more and more offspring. After a while, the population will now mostly be made up of this variety, and so it will have changed (evolved). Most of these changes aren't enough to make a "new" species, they just modify the original species over time as the world varies.

But, suppose that a part of the original population gets isolated somehow - part of the forest dies out and traps them in a relatively small area, where they no longer have any contact with the rest of the species. Or some individuals get blown out to sea by a storm and land on an island where they can survive with little or no competition. Or whatever; the point is that they continue to change over time in response to the pressures of life where they are, and the original population does the same. If the selective pressures on each are different; if the available varieties within each population are different; if the populations diverge over time, then at some point, they may be recognized as different species. Selection drives evolution (=change over time) and evolution may result in speciation if certain conditions are met (primarily reproductive isolation).

Note that it may look like evolution is 'directed', but that's misleading - we don't see the failures; we only see the end result and then say "of course it had to come out that way!" This is particularly a problem with the fossil record, where only a very, very, teeny-tiny, unbelievably small number of the things alive at any given time happen to be preserved for us to find later (probably a bit here and a piece there, at that). If we have only a small number of examples, what do they tell us about the species? Suppose that some time down the road, alien researchers find some human remains from two sites - one has the mortal remains of Yao Ming and Grace Jones, the other fragmentary remains of a man who stood 5'6" and a woman who was about 5'1". If those were the best examples of humans they had, they would probably define contemporary humans as two species: Homo altitudina and Homo minima (or whatever equivalent terms they used in their weird alien language, of course...), and make up lots of interesting stories about the life cycles of these two different species.

Well, this essay has turned out longer than I expected, so I'll drop it here. If you want some nice, interesting story-telling on evolution, I suggest you dip into SJ Gould's stuff. It's a good place to start. Just remember that scientists are very much like religiousists in that nobody agrees on all the details and sometimes disagreements get a bit noisy. Luckily, scientists have yet to start world-wide holy wars over their disagreements, although there are occasional fist-fights and lots of name-calling. I think the difference is mainly that scientists are generally beer (or whiskey) drinkers, while religiousists tend to suck down a lot of wine. Never trust a heavy wine drinker, is my motto.

Answer 6

Actually, it's still random. A bacteria that acquired a mutation survives and passes on genes that help it and its descendants to resist a certain medication. All the other bacteria without the mutation dies. But because the reproduction cycle of bacteria is so short, the mutation spreads like wildfire in weeks, instead of like in people, where it takes generations and thousands of years. And what is is about sea creatures? It took them millions of years (like the evolution of whales) and lots of mistakes to get there.

Answer 7

Mutations are random, but selection for or against the new mutations are not random. When a bacteria develops a mutation that gives it drug resistance, it is highly likely to survive and replicate while the other bacteria may die. The drug resistant bacteria then replicates, creating clones of itself. Evolution is not random, mutations are random that allow for adaptations (in animals over millions of years) to a changing world.

Answer 8

"but if you look at some cases like the evolution of sea creatures or drug-resisting bacteria...it's like they realized that in order to survive a specific trait must be acquired and the genetic sequence changed accordingly...

where did I go wrong? what am I missing?"



you looking at it retrospectively...





if you flip a coin and it lands on heads you can't go "WOW! how did it KNOW to land on heads!!?!!"

Answer 9

Mutations are not rare or occasional they happen constantly and are the source of genetic variation in a population. This means that every individual in every generation harbors some slight genetic variation. The mutations are not all different from each other but they differ from their source sequence. Many mutations repeat but one appears in a new combination of traits or appears in a habitat it suits better so survives to spread into the gene pool.



Mutations are beneficial with respect the current genome and to the environmental condition that does the selection. The selection is not random.



The survival of phenotypic alleles in the gene pool is driven by the selective pressures of the environment.





There is a steady number of mutations that appear depending on the fidelity of DNA replication, the number of crossover insertions/deletions, and the various transposition elements.

The actual mutation rate will vary between sexually reproducing eukaryotes, asexual eukaryotes and the prokaryotic asexually reproductive bacteria but there is one.



In humans a conservative average mutation rate was estimated to be ~2.5 x 10 ^-8 mutations per nucleotide site or 175 mutations per individual per generation, less conservative estimates range up to 2000 per person per generation. David Futuyma estimates each person is born with at least 350 new mutations that differ from their parent's.



Given the mutations must be in the DNA that impacts the phenotype to be under selective pressures the rate is roughly one mutation per 10,000 genes per generation. With nearly 30,000 genes, this means that each person harbors about three new phenotype mutations.

http://www.genetics.org/cgi/content/full/156/1/297



Larry Moran on random appearance of mutations & mutation rates in bacteria

http://sandwalk.blogspot.com/2007/07/mutation-rates.html

Modulation of mutation rates in bacteria – stable conditions select strains with low mutation rates, unstable select moderately high rates stabilizing the shift by removing the strains with the highest rates of mutation as well as the lowest.

http://arstechnica.com/science/news/2009/12/balancing-rapid-evolution-and-high-mutation.ars

'Mutation rates: When the going gets tough, beneficial mutations get going'

http://www.nature.com/hdy/journal/v99/n4/full/6801042a.html

Answer 10

I really don't get it why people in the 21th century still believe in the evolution. It is needed just little logic to figure out that evolution is not true.



Charles Darwin was just an amateur biologist, who was inspired with Malthus theory (that says that people if they want to survive in earth the number should be decreased- Survive the wealth population with the end of the poor one- in one word "war for Survival".) This inspiration Darwin wrote in his book. And its easy to understand from the Darwin theory too. All the theory from the beginning to the end have to do with the "war for Survival" (how the most strong animals survive compared to the small unprotected animals) But this theory has a lot to do with politics like Hitler, Stalin etc etc and all those whose slogans was war for Survival ( Hitler wanted to kill all the Jewish nationality)



But what is most important the biological concept, it has no logic - From nothing to something ( From dead- to live creatures). There is no evidence (Fossil) that mediate the creatures. For example: The "animals" from earth started FLYING (there was no fossil found of any creature that mediate the earth and air animals - if it were any it has to be an animal with wings - ex: Horse with Wings ops this looks familiar, I saw it in Cartoons- so if we believe the evolution, we also should think that life is a carton..) so NO, The Darwin theory is not True, it has no sense, No logic, NO nothing in it.)