In Evolution, how does the genetic material of the body know that a change is needed?

Question

I've been studying Evolution for a little while, and I've fully grasped the concept. I have a few questions about how Natural Selection works, however. I'm hoping someone can help me get the answer.

The genetics passed down from generation to generation give the traits to form the body thanks to genomes. What I'm trying to figure out is how they are "told" that a change is needed to the genetic code for their offspring's use.

For example, if a bug (lets say a wingless ladybug) had a very rough life on the ground and was highly susceptible to prey, it would need some form of escape mechanism. How do the genomes get told, from generation to generation, to grow appendages which would form wings, several thousands of year later? Is it years of trial and error with random changes to the body? Specific changes depending on the situation? And HOW are they told these are needed (it's not like you can say to yourself "You know, flight would be a real handy ability for me" and your genomes get at it)?

10 points and a big thanks to the best answer.

Answer 1

Genetic changes (AKA mutations), are random, and have no direction. I repeat: mutations are random. They happen at random, with no prompting or interface with the environment. They cannot be anything but random; mutations are the results of "dumb," molecular -scale, events.



The directionality of evolution comes from natural selection. What happens is that as mutations crop up in populations, they are acted on by natural selection*. The beneficial, adaptive mutations are selected for, and eventually become widespread through the population. To put it another way, the organisms that have beneficial mutations survive and have babies, while the rest of the population does not (or at least not as much). The net result is that over time you get a population that A) changes over time and B) develops genetic adaptations to it's environment.



As a matter of fact, this process -- the adaptive selection of random mutations -- is the reason scientists have been utterly sure about the validity of evolution since 1940 or so**. Simply put, mutations and adaptive selection are THE driving force behind evolution. If a living systems has those two forces acting on it, it WILL evolve. Since observed life has both, we know that it evolves.







*Unless they aren't. Sometimes mutations crop up in a population and aren't selected for or against; they simply "float" in the population, somewhat at random. However, these mutations CAN be selected for later. These "floating" mutations serve as pools of genetic diversity for populations to "use" under periods of novel selection. For instance, say that you had a population of cockroaches in Medieval times. In one of these cockroaches, a mutation crops up that gives a cockroach resistance to a insecticide that will be invented 400 years later. Now, this mutation doesn't help when in evolves, but you can see how it would be useful at a later date. In the most extreme example mutation survived in .1% of the cockroach population, and humans treated 100% of the cockroaches with the pesticide, then that .1% of cockroaches would abruptly become 100% of the population.



** Look up "The modern evolutionary synthesis."

Answer 2

Indeed, it's not like the genomes get told. Evolution isn't a driven, sentient process. It arises from a mutation, nothing more. It's a random sort of thing (I suppose you could consider it "trial-and-error" as you stated)



However, the thing that causes evolution is when this mutation will give the individual organism an advantage over all the others. This advantage will make it more likely to survive and therefore pass on its genetic information (AND the mutation) to the next generation, who will also possess the mutation.



The mutation spreads, the organisms without it are less likely to survive (through natural selection and competition) and become less and less prevalent and thus the animal is seen to evolve. Eventually the mutation becomes so pronounced that the "evolved" individuals are genetically incompatible with the originals. If this is the case, and they cannot interbreed then a new species is considered to have evolved from the old. You're spot on when you say that it takes a very long time.



It's most evident in bacteria and viruses due to their relatively short lifespan and high reproductivity.



Hopefully that was clear enough? :)

Answer 3

I would be very cautious with the claim "I've fully grasped the concept." It is great that you recognize understanding as the *goal* ... but when something really doesn't make sense to you, then you clearly have not yet "fully grasped the concept." I don't mean this as a criticism in the slightest ... only a caution that you can't fully claim to have "grasped" a concept until the pieces all start fitting into place.



The reason this is REALLY important, is that too many people feel they "grasp" evolution just well enough to conclude that "it doesn't make sense" ... and then decide that they no longer have to learn anything further about it. The anti-evolution community makes this a cornerstone of their arguments ... and they can't even see what a self-contradiction it is to say "I understand evolution perfectly, and I just don't get it."



In this case, it is REALLY important to understand that nothing is "told" when to produce some new genetic material. New genetic combinations are happening all the time. This happens in mutations. And it happens with every new mating in a sexually reproducing species (every offspring is potentially a brand new combination of genes that has never existed before).



Natural selection is only selecting the small number of these little changes that produces some slight advantage.



Another caution ... while we often use singular language to refer to a species (e.g. "the wingless ladybug" or "the arctic fox" or "the Indian elephant" when referring to a species consisting of tens of thousands of individuals), be very careful with this when thinking about evolution. Evolution is about what happens to a *POPULATION* of individuals ... like a species. When you keep this in mind, then you are less likely to think of changes in species as some sort of "decision" made by "the ladybug" ... because you recognize that *SPECIES DON'T MAKE CONSCIOUS DECISIONS*.





So with all that, we can answer your question. Your wingless ladybug species doesn't START with a need (flight), and THEN set out to produce it. The feature of flight evolves gradually because the need to be light and elusive produces enough advantage from generation to generation, that a *trend* develops that eventually leads to flight.



Aside: The evolution of insect flight is a very big topic, and it would take some time to explain it. I'll only say that it does not evolve *independently* in every insect species! Insect flight is something shared by many branches of insects, some of which have actually *lost* the ability for flight because they have found other niches where flight is not needed ... but these insects still have the *genes* for producing wings. Again, I don't want to give a long course in anatomical genetics here.



So never think of evolution as "NEED first, SOLUTION later." That is putting the cart before the horse. It is always about slow, incremental changes to existing structures, where nature selects (hence "natural selection") each change that provides small advantage.

Answer 4

The key concept is exaptation -- structure which has one primary function becomes increasingly useful for another function, until the new function becomes the primary usage.



Let's take your "wingless ladybug" example, but let's not give it the name of any living animal because this will be hypothetical only. There are a variety of strategies for evading ground predators. Let's assume there are two -- leaping away and climbing. The problem with leaping away is that attach from behind are from a blind spot because the body blocks the eyes. A subpopulation has some hair-like protrusions that started as a few extra cells on the back. The usefulness is those protrusions let them feel the attack coming slightly earlier, so they are slightly more likely to leap away in time.



Let's consider climbing. Small animals do not need to worry about falling; air resistance limits speeds. Wing don't impact climbing survival directly. Assume there is a predator that can climb and pursue including leaping after our animal. Leaping away works, but not always because the predator may still catch them. The animals with the protrusion way be able to leap farther in a light breeze (or stronger) because of the increased air resistance. Longer protrusions result in longer flights and increased survival. Some of the animals gain the ability to splay the protrusions, decreasing and increasing air resistance. They can get a stronger initial leap, then glide farther by adjusting air resistance. Now that air resistance isn't a problem, the protrusion can increase in area. Because it can be positioned, it can be longer without getting in the way during walking. It is a rudimentary wing. The muscle that adjusts the resistance can be twitched to extend leaps, then ultimately flapped for flight from a level surface -- a "full" wing.



Each of these steps involves adding minor functional increases to a structure that started as a few extra cells. I did not go into any developmental genetics because this is speculative enough that details are wasted. Evolution is simply the accumulated (or discarded) advantages that allowed lines to survive.

Answer 5

They are not "told." Evolution has no goal in mind (it is not teleological), but is the result of the "best" variations being chosen by Natural Selection. Reproduction produces variations by chance, but evolution refines and perfects those variations according to the pressures of the environment.



Some ladybugs might be produced with tiny variations that might lead to the development of wings several thousands of generation in the future; some may be born with variations that might lead to gills or that might lead to extra antennae. The gills or antennae are not necesarily useful- there is no positive selective pressure for those ladybugs to survive longer. But, those that have the tiny start of wings just MIGHT be able to escape predators better, somehow. They reproduce more offspring, some of whom have even larger wing variations. Natural Selection has determined the "direction" of evolution.



Virtually every character of every organism you see has been selected for by one pressure or another...

Answer 6

magicman...,



You are a thinker, and I like that.

How vastly possible is this theory of evolution, which postulates that present day organisms

underwent drastic evolutionary changes which today is why some organisms (including man/woman)

are the way they are today?

Some even theorize that after these organisms developed some body-tools, which made them at an advantage above their original state, they couldn't mate with their original mates any more.These kinds of positions only brew more confusion, instead of a thorough organised form of knowledge (what science is about).

Evolution took place alright, but it's not as drastic as Science thinks it was. By drastic I mean the situation whereby ammonium salts, or methane, water, and oxygen went on to form other organisms and then Man? That's like adding too much drama to the plot.

There's more to evolution than just theories. The orchestrated organisation from the minutest non-living crystals to the most complex of living machines is no accident. It wouldn't be too much to say man was MAN from the days of before-yore. He did not 'sprout' from great apes. Rather, he only did away with those things he did not need, and groomed those things which he needed as a result of constant use. Of course territorial organisation and civilisation also contributed to our advancement. It is imperative to know that higher forces were involved (and have always been involved) in the activities of living things. But I wouldn't like to venture into the religious, now, so as not to make some of us feel G-d is not perfect.

Okay, if we agree that our bodies were formed by evolving processes, how about the 'life force' in us? Did that also evolve with our bodies?

Considering the logic of natural selection, I think if it was the 'best of us' that is left in the world today, there shouldn't be much of the diseases and health disorders that plagues us in today's modern world. Though we might want to hide under the cloak of science and technology making us more sedentary and less fit, it still is not a plausible reason.

If majority of our forbears were the ones that had better 'genes' than their mates, then we shouldn't be this weak. We'd be a generatiion of super men.

My point, magic, is that your question already has its answer in it. For example, you used the wingless bug becoming winged. What I think is that there were winged bugs and there were wingless creatures. What most likely happened is the wingless bugs remained wingless while some wingless mated with the winged ones, thereby giving rise to winged and wingless ones. As can be sure, the 'new generation' winged ones had a slight advantage over the wingless ones. This made room for better survival of a majority of them over the wingless ones as a result of better body-tools of escape from predators and disease. You can as well finish the story by saying 'and the cycle continues'.

People who can think for themselves are what our world needs in order to make a better world. Not ideas that are rammed down one's throat, even when it is poked with holes.