How do we define a "new" species.

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People, please look at the Style Guide for EvC thread by Sylas. Pay particular attention to step 3.

I read that dogs and wolves can interbreed. Why are they considered different species?Also, can you shed any light on the peculiarity of the sterile mule?

They key here is that the concept of species is something that man has invented to try to catalogue living things rather than something that natures follows as a rule to what can and cannot breed.The only thing preventing a cat and a similar sized dog from breeding is that their DNA is too different. Dog and wolf DNA just happens to be similar enough to allow them to breed in some cases. Horses and donkeys have DNA close enough to breed but not have their offspring be fertile. It is a continuium rather than a discrete process that prevents animals from breeding. Some dogs and wolves are more similar than horses and donkeys.Even though certain individuals cannot breed we can still call them the same species. Due to a genetic difference my Grandmother and Grandfather could concieve but not carry a child to term without help from medical science. Just because they could not breed does not mean that they are not both still considered human. Their DNA was mostly similar except for one particular part of it that controlled what blood type they were. This is important because it shows that DNA can be in some cases very different (dog/wolf) and allow breeding or only be different in one small case to disallow breeding.Overall, nature does not recognize the categories we use to define a species. This is why it is so hard to just use one definition of species when talking about biodiversity because there are these weird exceptions. That is why we use breeding AND morphological differences AND reproductive isolation, etc when trying to pin down what a species is for OUR purposes of catalogue.

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Now is the winter of your discontent!
-- Stewie Griffin

Remember, evolution is simply a history looking backwards. It's just the story of what DID happen. Since evolution deals with populations of critters and not individuals, what we see is the results of those that did reproduce successfuly. There are two things going on simultaneously, and they are unrelated. Mutations happen all the time, and Natural Selection filters out part of the population. What is left ater the filtering is the record we see, Did they? It's not a competition. It's not that humans gained an advantage over chimps, it's that humans and chimps each evolved from some other critter. Two separate and unrelated paths and processes. We both changed and changed enough that our lines, Homo sapiens sapiens and Pan, continued while our ancestor, died off. Well, not actually monkeys, they still have the tails. But there is a valid question whether humans, chimps, gorillas and bonobos should all be classified in the same group, either all in Pan or all in Homo.

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Aslan is not a Tame Lion

Note the important difference in the these quotes. One is "a group that interbreed" that is they do interbreed the other is a group that can interbreed. Part of the biological species concept is that the breeding occurs in the wild naturally.Dogs and wolves, however, do breed naturally. In this case the incipient species has been separated out early. Remember, one species (most of the time) blends (over time) imperceptibly into the new one forming. When you decide a new one has formed is a matter of judegment. We probably separate dogs off because of non breeding reasons and because we are interested in them.Google for a definition of "species" and you will find many pages of discussion on trying to find a good definition.Remember that after species all the higher levels of taxonomy are for convenience of finding information and our tendancy to want to group things. The only "real" part of taxonomy is the commonality of descent. However, after enough time a lot of the details of that have been lost so we have trouble deciding when to split or group species under one heading or another.Why is the sterile mule in anyway "peculiar"?This message has been edited by NosyNed, 01-25-2005 20:48 AM

Quote: It's not a competitionOkay, if two species "evolve" on different sides of a mountain range,
eventually they will meet one another, and at that time, which ever one has advanced the most will dominate for resources and supremecy. So it is a race, isn't it? Who can become the most highly adapted the quickest? What if monkies had learned how to weild spears and axes? According to evolution, they would become the top species, right? Or am I wrong? I hate having to ask that, but although I beleive in Creationism, I still try to learn all I can about evolution.

Maybe that will happen.It may also be that one side of the mountain was dryer and one wetter. Where they meet may have both enviroments side by side and the "dry" species will predominate in the dry areas and the "wet" in the others.Perhaps while evolving separately one has picked up on an insect common on one side and not on the other. By the time they meet they may co exist without direct competition.Or as noted above they may. In which case one may intrude on the other.What would happen if different events had taken place in the past is an interesting question. Gould suggested that with some many contingencies occuring the type of things that would evolve the next time would not be just like the ones that did last time.That is almost certainly true. However, the many instances of convergent evolution show that many things would be like what exists now. Eyes have evolved separately a bunch of times (like maybe 40). The necessity for streamlining would ensure that there would be fish shaped things in the seas even if they would not be the fishes we see.However, somethings may not happen a second time around. Intelligence has been suggested as one of them. We don't know. Well, using the word "monkies" very very losely I would have to say they did. And you're right they are much, more numerous than their cousins who didn't.

If two species meet, there is a good chance there will be competition for resources, if the two species hold similar niches or use the same resources. If they don't use the same resources, they might be able to coexist.In modern times, people have brought plants and animals from all over the world to all over the rest of the world, and those species take over their new environment. It isn't really a matter of one species being better or more "advanced" than the other. The old environment of the alien species might give the same resources, but without the competition that it has evolved alongside, so the alien species takes over the new environment easily. An example would be bullfrogs in Australia. Someone brought a couple bullfrogs and they were able to reproduce rapidly and do tremendous damage to the environment there. Another would be kudzu, which is spreading all over the Eastern United States. Native to Japan and China, it isn't so much of a problem there. Over here though, nothing eats it and it spreads everywhere.Now if we brought whatever lives in Asia and eats kudzu over here, it might spread really well and kill some native species and screw things up even more. Then we'd probably have tons of kudzu and some nasty wasp or something.Now, about the monkies, I've heard of baboons beating each other with sticks. So they've probably learned a little about using objects as weapons. Humans might have started out with weapons in the same way, though they probably weren't humans the same way you or I are. It was probably millions of years ago when tool use became prevalent among hominids.We are classified with the great apes in the family Hominidae, and we share many similarities with them that indicate that we share a common ancestor with the apes. This is supported by both genetic and fossil evidence.This message has been edited by Gary, 01-25-2005 22:05 AM

While that is one possibility it is not the most common outcome. One great example is to look at the primates. The humans, chimps, gorillas and bonobos all developed in pretty much the same area and over about the same period. But each occupied a different ecological niche. You can see it in some of the other primates as well, where many different species of monkey live in the same area.In fact, in most cases many different species live side by side without one species wiping out the other. Just look most anywhere. Look at the variety of antelope that exist side-by-side, or big cats, lions, cheetahs and leopards that we are all familar with but also the smaller serval, caracal, swamp cat, golden cat, sand cat and secretive black-footed cat.Look at the plant world where many species make up an environment and at the world of birds, or butterflies, the number of bats that live side-by-side. In Texas alone there are 33 species of bats, 484 species of birds and over 300 species of butterflies that live down here in the Rio Grande Valley.The most common thing we see is not one species dominating over another but rather each species living within a unique niche.

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Aslan is not a Tame Lion

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In modern times, people have brought plants and animals from all over the world to all over the rest of the world, and those species take over their new environment. It isn't really a matter of one species being better or more "advanced" than the other. The old environment of the alien species might give the same resources, but without the competition that it has evolved alongside, so the alien species takes over the new environment easily. An example would be bullfrogs in Australia. Someone brought a couple bullfrogs and they were able to reproduce rapidly and do tremendous damage to the environment there. Another would be kudzu, which is spreading all over the Eastern United States. Native to Japan and China, it isn't so much of a problem there. Over here though, nothing eats it and it spreads everywhere.

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OT, just a thought that crosses my mind...I don't know whether some predator regularly eats chimps and gorillas, but I think we have good evidence that australopiths were eaten by leopards and eagles.Could it be that our ancestors spread throughout the world after they discover some patch of Africa (or elsewhere) where nothing eats them? I mean, I envision the early dispersal of ancient humans as somthing like the spread of an introduced species, we just spread and multiply and smother everyone else...

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I don't know whether some predator regularly eats chimps and gorillas, but I think we have good evidence that australopiths were eaten by leopards and eagles.

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The predator is determined by the niche. Chimps are more arboreal so they are threatened less by predators found in the ground. Gorillas eat roots, grasses, and leaves and are more prone to predators found on the ground (they do retreat into trees at times, though). The homonids, however, seemed to adapt to an open plain environment. "Lucy", for example, has feet like us and probably walked in a very similar fashion given the angle of the femur and hip.

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Could it be that our ancestors spread throughout the world after they discover some patch of Africa (or elsewhere) where nothing eats them?

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The start of human migration probably occured by following the coast from Africa into Arabia. From arabia they spread into asia. I think the migration of humans had more to do with technology and societal constructs than it did from the absence of predators. There were ferocious predators throughout Asia, for example, and yet they moved there with ease.

I thought there might be some more technical reason--some physical difference. A wolf looks exactly like a dog to me.As regards the mule, I thought this was a special case. That donkeys and horses breed and produce this sterile blend. I assume donkeys and horses are different species?

Which dog? My purely personal opinion is that dogs are already more than one species. This is just a case where the two species are close enough to produce offspring but not close enough to produce fertile offspring. I think it has been mentioned in a number of threads that speciation is not (usuall) an instantaneous thing. The "mule" case is, I'm guessing, going to happen a lot. The only reason we are more aware of this one is that we have domesticated both animals and keep them in close proximaty.

Really - you mistake wolves for dogs? But in any case, this emphasizes the issue of simply using "looks-like" or morphology-based species definitions. Many organisms have evolved to look exactly like another (mimicry), but an organism and its mimic could never produce offspring due to DNA-level reproductively incompatibilities. In other cases there are species that look quite different and but are still capable of mating and producing healthy offspring despite their overt morphological differences. Many crosses between two different species produce sterile offspring. I have seen some species definitions that reflect this by specifying the production of fertile offspring.

Yeah, what I am trying to figure out is if there is some physical reason why two species can't breed--like a chemical reason or something.So I guess the mule is just a famous case. Why are they sterile?