by pirata 10 Replies latest jw friends
I've heard the distinction between microevolution and macroevolution a lot, especially from Intelligent Design arguments. Microevolution being defined as changes or adaption within a species, and macroevolution being changes from one species to another
My impression is that there really is no such meaningfule distinction between macro and micro in the modern scientific sense of evolutionary theory. "macro" evolution is the result of small changes over time.
Thoughts?
This is one of the best ways I've seen to explain/demonstrate micro vs. macro evolution...
Also illustrates the fault in asking "where are the transitional fossils?"
I like to think of it as walking. Whether you're walking to your mailbox at the end of your driveway or across town, it's the exact same process. There is no physical point an arbitrary distance from your house that you cannot walk across, and likewise there is no evidence to suggest some kind of barrier that prevents the accumulation of small changes over generations to diversify a population to the point where the descendents of a single species bear little resemblance to each other.
I've never understood how it's possible to accept micro but not macro given that one logically results in the other.
@Pirata: that is correct. Whenever speciation occurs, it is macro. Anything smaller is micro. The accumulation of small changes with time may eventually lead to macro (speciation), but it isn't a necessity (unless environmental pressures push it).
I'm noticing more and more witnesses willing to accept "micro" but not "macro." Granted, many of these are ill-informed as to what the implications of either really are. These are also the same ones who will use the word "adaptation" but not the word "evolution."
I'm noticing more and more witnesses willing to accept "micro" but not "macro." Granted, many of these are ill-informed as to what the implications of either really are. These are also the same ones who will use the word "adaptation" but not the word "evolution."
There was the special issue of the Awake! a few years ago that discussed the finches demonstrated, "at best" the ability to adapt to the environment. When I read that, I realized that they were admitting that the basic evolutionary processes do indeed happen. I also remember reading about the different "kinds" of dogs that came from one dog pair in the "You can Live Forever" book. Same thing.
@ unshackled: Love that explanation!!!
I've noticed JW's are willing to commit to "adaptation", but mention the word "evolution" and they get visions of apes turning into humans and dinosaurs turning into birds...in a *snap*, of course. Like one day, an ape just gave birth to a human and a land dinosaur sprouted wings and flew. They are completely misunderstood about the reality of the evolution theory.
Macro-evolution is speciation. As soon as a species has evolved to the point of no longer being able to interbreed with those whom it evolved from that is macro-evolution. The problem with people who don't accept evolution is they think that macro-evolution is where all of a sudden a lizard is going to give birth to a chicken or a chicken is going to give birth to a dog, they don't realize all the steps it takes to get to that point. I wrote something a few months ago with an example of how "macro-evolution" occurs. You might find it helpful...
I'm going to do this in steps.
1.) A small bird is located in Chile, it is a herbivore (eats plants) and is yellow in color. This bird is well adapted to it's environment because there is a yellow plant in Chile that is it's primary food source. This plant is abundant so being an herbivore the bird has plenty of food surrounding it and since it's primary food source is yellow it's camoflaged from predators.
2.) A volcano errupts in Chile and makes the environment unsuitable for the birds, so they start migrating northwards. Since it's a small bird the ones that don't have stronger wings don't survive the migration or stay in Chile. The migrating birds enter Brazil. In Brazil they encounter the rainforest, because of the rainforest being lush in green plant-life the birds yellow color makes it a target for predators. Luckily only the stronger flyers made the trip so their defense is to now escape quickly, however through generations an allele change occurs by this species interbreeding with a similar bird. This allele changes the birds color to a deep green. Obviously since green fits in to their environment better, less of the green colored birds are going to get eaten so more of those will reproduce. Competition is fierce in the Amazon so the species again starts a migration northwards. Now let's track, what changed here? The bird now has a different defense mechanism, it's diet has changed, and it is now a different color.
3.) The migrating birds now come to Honduras where they stumble upon a purple flower that is actually a relative of the yellow flower they were previously dieting on in Chile. The green color is good to prevent predators but not great in the Honduran area. A recessive gene in the previous species they had interbred with had an allele that made the bird's color purple, through a regression a few of the birds turn purple. Again predators to this bird are not going to find the purple birds as much as they would find the green ones now that their primary diet is found on a purple flower. So what changed here? The bird actually regressed to a trait from their interbred species and turned purple, a beneficial mutation in the area they're located.
4.) A drought in Honduras causes the purple flower, the chief diet staple of our birds to rapidly die off. The birds in order to survive again start migrating North. They find a similar habitat on the Coast of Mexico. However there is not abundant plant-life in this area due to the high salt water content in the soil. The birds forced with starvation start ingesting small incects. Due to the incects now being introduced to their diet, a formerly dormant organ in the birds digestive system activates to allow them to digest the incects more efficiently. This activation of the organ actually makes the bird slightly larger than it was previously. The birds with harder beaks can eat a wider variety of incects and the females of the species are selective in their breeding, there-by they only select the healthiest for their mates. The healthiest being those with harder beaks since they eat more. Living on the Ocean causes yet another change as they interbreed with a close relative of the other species they had interbred with. This causes the hybrids to carry the other species coloring which is a dark blue and also small teeth-like ridges on their beaks which help them even more with their digesting of incects. So what changed here? They changed their diet and now are carnivores, they became bigger, changed color and have small "teeth".
5.) Once again fierce competition for food grows as the population of this bird explodes. The migration northwards begins and the bird now is found in Florida. A funny thing happens in Florida, due to the high incect population the bird flourishes but this actually causes a fierce competition for the females attention. A random mutation in the genome occurs and a few of the birds are born with a bright red color. This does hurt them on the predator front but for mating it seems that the chicks dig it (Pun TOTALLY Intentional). The population now for the most part becomes red in color, due to the larger incects in Florida the birds with the larger "teeth" end up able to eat the larger incects and flourish greater than others. So what changed here? The birds once again changed color to a red color and their "teeth" became larger.
6.) This time we're going to take human intervention in to play, a pesticide that humans spray on the fruit grown in Florida causes a severe bottle-neck in the bird population. Those who survive were naturally resistant to this chemical but many that weren't began migrating North. They reach Rhode Island (Yay! Finally) here in RI they find fierce competition for territory with Hawks who dominate the higher perches. Ever since it's journey to Mexico where it became a Hunter it naturally scouted the highest ground but now because of the severe disadvantage it holds to Hawks the bird now finds it's nest on the ground. Predators find it easy to find this brightly colored birds and the bird is very nearly wiped out. However the birds with a duller shade of red seem to be harder to spot and eventually the birds coat becomes brown. Rhode Island is only abundant in the summer for incect life, in order to survive the bird needs to find a new source of food. They find that in the common mouse. The larger "teeth" come in handy here to tear apart the prey and those with larger "teeth" and claws become the stronger of the species and hence the ones the females choose to breed with. Their previous digestive organ that activated in order to digest incects now goes into overdrive and actually divides into two chambers. By the time the bird can compete with the Hawk for dominance it's instinct had already been formed to nest on the ground. So what changed here? The bird is now brown due to the dulling of their color so predators couldn't eat them, their diet changed and their digestive tract changed, they now have nearly full blown "teeth" and claws.
Now I know all of you are saying "That's not evolution", "It started a bird and it's still a bird", "These are all little changes". I know they are, they are small changes and the species is still a bird but THAT IS WHAT EVOLUTION IS! The biggest tell-tale sign in this example is if you take the yellow bird from Chile it can still breed with the bird from Brazil but it can't breed with the bird from Mexico, the bird from Mexico can breed with the bird from Florida but not the one from Rhode Island. Certainly the bird from Chile can't breed with the bird from Rhode Island. This is something called speciation, when one species evolves to the point where they can no longer interbreed. It's like the difference between a house cat and a Lion. It's clear they share a common ancestor but they can't breed with each other and you would clearly consider them different species. In fact if you took the bird from RI, the carnivor with "teeth" and claws that nested on the ground and feasted on rodents and compared it with the small yellow bird from Chile that ate primarily one yellow flower you wouldn't even think one came from the other. That's where genetics would come in to play, it could prove the injection of different DNA, androgenous retro-vires etc.This is what alot of people say has never been seen "Macroevolution". Yet it's seen all the time, it's simply speciation. There is plenty of evidence for it as well, now if a change like the one I listed above can easily occur and you agree that the changes could take place (and by the way every single one of those changes happened in one species or another that has been documented) then imagine that bird being isolated in different environments, climate change of the earth and millions of years going by. Don't you think the species will become more and more disperate?
there really is no such meaningful distinction between macro and micro in the modern scientific sense of evolutionary theory. "macro" evolution is the result of small changes over time.
Precisely . . . the only variable is time.
Over great lengths of time, favorable micro-evolutionary changes become "bedded in" through changes in the selective environmental factors such as climate, food supply, competition etc. The adaptive changes that result in survival then become the "norm" from which further micro-evolutionary changes can occur. For a species to resort to the previous "norm" would need the whole raft of environmental factors that previously existed to be re-created, and even then survival cannot be assured unless it too proceeds gradually over time.
A great fallacy held by detractors is that one species "changes" into another, as if crossing some magical boundary. New species simply emerge gradually as micro-evolutionary changes lead it further away from it's previous "norm" over a lengthy period. Current species almost never exist alongside the species from which they evolved. In effect they ARE the species from which they evolved.
There is a good deal of mutual understanding on this thread. Without previous discussion or combined research, each poster has developed a very accurate understanding of the process which fits into a very similar definition. I feel that is significant.
