To expand on this, changes in the available available genetic material that produce differential traits need not be solely mutatory in origin. Myriad factors can combine to poduce changes in an animal that are not based on (or at least, not entirely on) a mutation. For example, there are traits known as quantitative, or ‘polygenic’ traits that are affected by a multitude of alleles at various loci. The net effect of these alleles is responsible for exhibited feature. A prime example would be weight in humans. No new mutations are required for weight to differ in an individual. A range of (possibly unrelated) genes from the mother and father have the net effect of providing an individual with their tendancy towards some weight. Assume for the sake of argument that eye color and hair color are the two genes that affect weight. Assume that blue eyed, red haired people are naturally fat. If some change in our environment in the U.S. favored fat people, whereas the African environment favored skinny people, red haired, blue eyed people would survive in America, whereas the thin people would survive in Africa. After enough time had passed, we would have two species of people, red haired fat people and skinny blond people.
Other possibilities for non-mutation based formation of novel genetic material include unequal crossing over during meiosis, which is one of the major sources of new genes when it results in duplications of chromosome segments, transpositions of chromosome segments, inversions, polyploidys (increases in the number of copies of the chromosome), etc.
The problem is that you’re thinking small. Given billions of years, anything that can happen to shape a genome will, eventually. This results in an incredible diversity of genomes.
Are we as a species (or a population of that species) currently in the process of evolving into a new species (or sub-species)?
Absolutely. All populations on earth are evolving. Constantly. Evolution never stops, because the frequencies of a gene are always changing. Everytime one person dies and another person lives, the human species has evolved, because the genetic composition of the population has changed.
Apologies for jumping in this late…
How about filter as an analogy. Not perfect I know but it’s a start.
Natural selection works over many generations of many individual animals to “filter” out the weak/slow/etc members of a species from the genepool.
Hope that helps.
I’d like to add an asterisk to that. It’s likely that evolution of the human species is slowing down. We can adapt to the environment through technology, without having to do so genetically. Certainly allelic frequencies are changing, but, without some sort of large scale disaster that we can’t adapt to through technology, it’s unlikely that we will speciate.
[aside]I’ve always thought that would make an interesting backdrop for a science fiction story: humans colonize Mars, but then some disaster (or even a change in political climate) stops the space program, cutting off the Mars population from the Earth population. Now that I think about it, I guess Asimov already did that in his Robot series (where the Spacers were somewhat different than the Earth humans, particularly on one isolationist planet).[/aside]
It’s not bad, but it only covers the “weeding out the bad” side of natural selection.
It isn’t exactly an analogy (it’s just a tweak to the same process), but I think a good place to start might be selective breeding. Do you believe that we have changed species through selective breeding, bodswood?
Also, I haven’t fully explored this link, but you might want to look into genetic algorithms. Basically, genetic algorithms use the principles of natural selection to “breed” computational solutions to problems. I guess I could quote the page:
Having followed this thread for a while thought I’d throw in a comment.
The previous discussions over the definition of a ‘species’ notwithstanding, it is unlikely that we are likely to evolve into something we would call a new species anytime soon. This is because, for the time being at least, we have elevated ourselves above the process of natural selection. We have become very good at providing survival resources (food, water, shelter, etc.) for a significant proportion of the population (it would be nice if we could do it for the entire population but that’s another matter). Also in a world of 6 billion there is someone for everyone, so finding a mate is a matter of course (I’ll let someone else add a witticism to this!). This social safety net means that the majority will reach reproductive maturity - the strong and the smart and the weak and the simple will all have children of their own. For us to evovle into a new species our environment would have to change significantly so that the competition for resources once again became a matter of life and death and those harsh conditions would have to persist for a long, long time. Even then, it is hard to imagine an environment, that did not lead to extinction, where our problem solving skills would be insufficient to ensure our survival as we are.
… it is unlikely that we will evolve into…
If proper English ever becomes a competitive survival advantage I’m toast. Sheesh.
Nope. Simply look around. Humans come in all shapes and sizes and colors. These are all expressions of the already-present degree of variation within our genome (as well as numerous environmental/developmental factors which are not necessarily inheritable). Nothing needs to be “new” at all. All that is necessary is for the environment to be such that one or more of those variations which already exist are now advantageous, relative to the “average”. Right now, there are no real selective pressures acting on humans which favor a specific height, for example (however, there are such pressures which serve to rule out any extreme variations – super-small or super-tall folks tend to have siginificant health problems, for example. This is a type of natural selection known as “stabilizing selection”). But, if the environment were to change such that one height direction or the other became advantageous, then the general trend in subsequent generations would be towards that height level. If smaller people were able to cope better in a given environment, then we would expect a general trend towards smaller people. A real-world example would be in tropical or other hot climates. Large body size tends not to fare as well in such environments because of heat dissipation issues. Thus, you tend to find either tall, gangly people, or short people, both of which can maximize surface area to volume ratios and thereby limit overheating.
That’s just it - the “proto-wing” is just an arm. Theropod dinosaurs (the familiar bipedal meat-eaters) begin to show trends in the arm structure related to flight almost from the beginning. The hand, the wrist, the arm bone proportions, all gradually and subtly change over time, even in the largest creatures such as T. rex. This is not to say that T. rex would ever have learned to fly, but the arm bones it had were already quite similar in form to what had already become a wing in a different lineage. The maniraptoran dinosaurs (such as the famous Velociraptor) had very bird-like arms and hands, despite them still not having wings: very long fingers and fewer of them, reduced thumb size, specialized wrist bones allowing them to fold their hands back along the ulna, fused clavicles resulting in a wishbone, and so on. Even the motion of the arm was becoming very similar to the flight stroke, despite it probably being used just to capture prey. And, we’ve found feathered dinosaurs, indicating that feathers themselves were already being used for other purposes, such as insulation, before they became useful for flight. Looking at the progression of threopod dinosaurs throughout the Mesozoic, we see very nice trends in terms of forelimbs being modified more and more towards flight. And at no point was the limb useless to the animal.
It seems that you are largely incredulous as a result of limited experience, so to speak, in the realms of paleontology or natural history. In other words, you seem to be concerned with the specifics of how such-and-such may have evolved before you’ve gotten the basics down. The key to understanding evolution is not in discovering the pathways by which everything, everywhere evolved, but in learning how evolution works in the first place. As you observed, natural selection is, indeed, the lynchpin which holds evolution together. Grasp NS, and everything else is easy. There are, of course, other associated concepts, such as the mechanisms which produce mutations and variation, and other evolutionary mechanisms such as genetic drift, but NS is the key concept.
Jon the Geek: ‘It’s likely that evolution of the human species is slowing down. We can adapt to the environment through technology, without having to do so genetically. Certainly allelic frequencies are changing, but, without some sort of large scale disaster that we can’t adapt to through technology, it’s unlikely that we will speciate.’
Somnambulist: ‘*t is unlikely that we are likely to evolve into something we would call a new species anytime soon. This is because, for the time being at least, we have elevated ourselves above the process of natural selection. We have become very good at providing survival resources (food, water, shelter, etc.) for a significant proportion of the population.’
There seems to be a measure of (hedged) agreement on this. But aren’t the changes that have been observed in the (approximately) 120,000 years of modern human history suggestive of continuing evolution? Given that evolution is a very very slow process anyway (120,000 years is a mere blink of the eye), don’t the fact that changes have occurred in those 120,000 years and the fact that some changes have occurred within even the last 10,000 years indicate that there is a probability that within say another 120,000 years or so we will speciate?
As talkorigins http://www.talkorigins.org/faqs/homs/species.html puts it:
'Modern forms of Homo sapiens first appear about 120,000 years ago. Modern humans have an average brain size of about 1350 cc. The forehead rises sharply, eyebrow ridges are very small or more usually absent, the chin is prominent, and the skeleton is very gracile. About 40,000 years ago, with the appearance of the Cro-Magnon culture, tool kits started becoming markedly more sophisticated, using a wider variety of raw materials such as bone and antler, and containing new implements for making clothing, engraving and sculpting. Fine artwork, in the form of decorated tools, beads, ivory carvings of humans and animals, clay figurines, musical instruments, and spectacular cave paintings appeared over the next 20,000 years. (Leakey 1994)
Even within the last 100,000 years, the long-term trends towards smaller molars and decreased robustness can be discerned. The face, jaw and teeth of Mesolithic humans (about 10,000 years ago) are about 10% more robust than ours. Upper Paleolithic humans (about 30,000 years ago) are about 20 to 30% more robust than the modern condition in Europe and Asia. These are considered modern humans, although they are sometimes termed “primitive”. Interestingly, some modern humans (aboriginal Australians) have tooth sizes more typical of archaic sapiens. The smallest tooth sizes are found in those areas where food-processing techniques have been used for the longest time. This is a probable example of natural selection which has occurred within the last 10,000 years (Brace 1983).’
With regard to the special argument concerning technology, since technological advances have only kicked in in the last hundred years or so (during which time there has been a commensurable explosion in global population), this would surely have had as yet no effect on the changes that have been taking place for the past 120,000 years.
Then what of the case of populations, such as those in South America, who have not yet been exposed to technology? If they retain their isolation, will they not evolve as a separate sub-species? We, or at least our descendants, might be able to save ourselves the price of a return trip to Mars by just catching an A.A. flight to Brasilia.
We will eventually speciate, of course. In a hundred million years, we won’t be the same H. sapiens.
One thing, please: There is NO such thing as a subspecies! It is an outmoded concept.
Other than that, I like the way you’re mind is working with the TalkOrigins material.
EXCELLENT reply, bodswood. Were you playing Devil’s advocate, or did are you starting to accept some of the things you said in there?
Yes, it’s possible that humanity will speciate without any huge natural disaster. I think it’s unlikely, but that’s really nothing more than an educated guess, based on the progress of the last 100 years or so. I think we’ll probably remove selective pressures on humanity worldwide before we’ve had time to speciate, but I fully admit that I don’t know.
Let’s just pretend that Somnambulist and I were trying to teach you the next lesson: it is impossible to predict future paths of evolution without having all of the facts (which we are unlikely to ever have). Will humanity speciate? Who knows. I don’t personally think it’s likely (again, without some sort of isolating incident), but I could easily be wrong.
Will isolated populations, such as those in South America, assuming they remain isolated, speciate earlier than populations exposed to technology?
Actually, J-the-G, the fact that you, the sleepwalker and Ilsa show some disagreement about the future of the human ‘race’ accords with my ideas about the paths of scientific progress, or, indeed, of knowledge in general.
Devil’s Advocate. Wasn’t that a film with some famous actors?
And Keanu Reeves.
If they remain isolated they will more than likely speciate. Wheter they will remain isolated is an unknown variable, though.
This is a rather specious way to attack scientific method. Uncertainty about the future is caused by a lack of data and in itself does not cast doubt on what can be discerned from the evidence.
Do you know for sure where you will be and what you will be doing in 20 years? If you can’t be sure of your future that means you can’t be certain about your past and present?
To bring it back to evolution, the fact that we can’t be sure what our descendants will be like doesn’t mean we can’t be certain what our ancestors were like.
It also had Al Pacino and a naked Charlize Theron.
In his article ‘What is natural selection? A plea for clarification’, Neil Broom (author of How Blind is the Watchmaker?) deals with the thorny issue of intentionality versus purposelessness and NS in his discussion of natural selection with reference, in particular, but not only, to Dawkins’ ideas. Thus, on p. 7:
‘So this is the predicament that confronts naturalism: it desperately needs something more than the unthinking, undirected forces that an entirely material universe can provide. But it dare not admit to this in public. In private, however, barely disguised in the images, narratives and metaphors it is compelled to use, it betrays this desperate need for a non-material or transcendent guiding principle in order to provide a coherent science of life.’
How valid are the points he makes?
The whole article is available at http://www.iscid.org/papers/Broom_WhatIs_031202.pdf
I can’t see how he makes any valid points at all. He seems to want to force an implication of intelligence into natural selection but I honestly can’t see why he thinks it’s necessary. The portion you quoted is patently false in its assertions. There is no “predicament facing naturalism” nor is there any need whatever for a “guiding principle.” It’s all just completely random. Broom seems to think that the results of evolution are the result of some sort of intention, that they represent some sort of end goal. They don’t.
I wonder if there are any other members of the scientific community who at least hold the view that Dawkins should have eschewed words that hinted at intentionality.
What words of Dawkins? Where? Which scientists thought this was a bad idea?
The author is confused. He misses the point of Dawkin’s analogies entirely, and mistakenly jumps to the conclusion that, therefore, some sort of "purpose’ is inherent in the system. It has been explained, numerous times in this very thread, what natural selection is and how it operates. So I ask you: how valid are the points that have been made by me and others? And how do *you * think they square with the author’s attempts at shoehorning in a purpose?
Many of the author’s counterpoints have likewise already been addressed here. (As an aside, would you therefore argue, as the author might, that this thread “knew” the direction it would take - that the “evolution” of our argument is such that the author’s conclusions have been refuted before they were even brought up…?) I discussed (very briefly) the evolution of bird’s wings, for example. No need for mysterious intermediates, with unknown functions. No need for presumed intention with respect to the trend in forearm evolution within theropods.
The author is even outright mistaken with respect to his understanding of NS:
Simply put, there is no reason why an organism “should” feel the need to avoid predation, procure nutrients or reproduce. But a moment’s thought will reveal how silly such an argument against NS is: any organism which doesn’t feel the need to avoid predation gets eaten! Any organism which fails to procure nutrients dies! Any organism which fails to feel the need to reproduce, doesn’t! Surely one would not be so confused as to how NS operates to suggest that such individuals, or their genes, will or should persist! So, the fact of the matter is that those organisms which feel the need to eat, not be eaten, and reproduce are the ones which stick around. It is not a matter of “should”, it is a matter of “do”, because those who “don’t” become inconsequential.
Much of the rest of the article is the author continuing to miss the point of analogies, or misinterpreting (or misrepresenting…) definitions. I again say that you have been given the definitions and workings of NS numerous times in this thread. Which elements of that mechanism would lead you to believe as the author of that article does? In what way is materialism compromised by the deifnitions as presented herein?