How do we define a "new" species.

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In the process of evolution, How can you justify that one creature's DNA is different than another?

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Because we can sequence the DNA, and those sequences are different.

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The whole process of evolution is dependant on the fact that animal's physical characteristics change through adaptation, right?

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No, the whole process is dependent on random mutations and natural selection. These two mechanisms CAUSE characteristics to change over time.

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Yet There are HUNDREDS of breeds of dogs that have purposefully had their physical traits selected and changed from the originals. Here's the problem, however, every single breed has the same DNA as the wolves and dingos ect.

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Umm, no they don't. In sexually reproducing animals, no offspring has the same DNA sequence as it's parents or siblings (barring identical twins which came from the same egg and sperm).

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I mean, we can't classify an animal as a new species unless it's DNA is different from it's parents, right?

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Species are defined as populations, not individuals. Species are defined by a group that interbreeds. Since different dogs interbreed, they are considered to be a single species. Species are not defined by their DNA but by the flow of DNA through each generation. Different species may even be able to produce fertile offspring. However, if they do not produce offspring in the wild, or very rarely do, they are considered different species. Again, it is a question of gene flow, not gene sequence.

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All animals carry the DNA their parents "flow" to them, right?

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Yes and no. The egg and sperm carry half of the parents DNA. Also, during the production of eggs and sperm, errors occur when the DNA is copied resulting in mutations. So the offspring carry a mixture of their parents DNA in addition to mutations not found in either of the parents.

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So if a Chimpanzee is born with a very long tail, and eventually it presents some kind of advantage over it's parents until it's parents can't compete, and then die, is that monkey a different species than it's parents?

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Nope, populations are species, not individuals. If a chimp is born with a tail, that tail must allow the chimp to have more children than chimps without tails in order to be deemed beneficial. As you can imagine, if the tail helps the chimp to gather better food, to be healthier, etc. it will probably also have more children. So, the children may also have this tail, through heredity. These children will also have a better chance of having children. Repeat this process over and over and soon you will find that most of the chimp population now has a tail. However, this is not speciation.

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I guess my real question to you guys is, at what point in the family tree, or at what generation gap can you consider a new species born?

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The production of a new species is a difficult thing to deny, yet it obviously happens (well, to us evos anyway). It is like asking when a hill becomes a mountain. If you put a 10 foot berm and Mt. Everest next to each other it is easy to see the difference. However, there are some hills that look a lot like mountains, and vice versa. Also, species form over time, not all at once. What constitutes a new species and what constitutes two separate living species are very different questions.

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A human can be born with brown hair while his parents have blonde hair, but he still inherited his DNA from them. Does it mean he is the new and improved super-homo-sapien?

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The definition of species has to do with reproduction. If this new human breeds with other humans it is still a human.

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So does every mutation that decided a new species according to the theory of evolution have to have increased the species ability to have children?

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No. Going back to the tail, the tail might have allowed some of the chimps to live in trees that are not accessible to non-tailed chimps. They will reproduce at the same rate, but in different niches. Speciation occurs when only the tailed chimps mate with each other, and consequently the non-tailed chimps mate with each other. This creates two separate gene pools which may result in large differences in morphology over time.As an analogy, let's look at oral traditions. Let's pretend that a culture had a certain story that was always being told around the campfire. Through migration, this culture split into two tribes that are on opposite sides of a mountain range. The two tribes only rarely talk to each other. Now, what is going to happen to that oral tradition? It is a common human trait to change stories between each telling, or between generations. But since these two tribes don't talk to each other, the changes will be different in each tribe. Over time, the stories will not resemble each other. Names, dates, and plots may change so that they are no longer recognizable as being derived from the same story. This is how isolated gene pools work, by isolating different changes in different gene pools.This message has been edited by Loudmouth, 01-25-2005 17:29 AM

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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.

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A "species" can be defined as an isolated gene pool---not isolated by some external factor, such as locale, but isolated because its DNA is not compatible with any other DNA. There are a few cases--such as wolves and dogs--which are accorded separate species-status more for traditional, cultural reasons rather than DNA incompatibility.

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It is still quite simple. Species are separate gene pools. Separate species do not interbreed in the wild, or very rarely interbreed. They may produce a viable offspring through artificial insemination, but this matters very little for the process of evolution. Gene isolation is gene isolation, no matter the reason. It is not a question of "if they can" but "do they". There are many reasons that separate species may not interbreed, one of which is DNA incompatibilities. Others may include sexual selection, physical incompatibility, egg/sperm recognition, and hybrid sterility.One example that is pseudo-famous is Darwin's finches. These finches are isolated in the Galapagos Islands made famous by Darwin (hence the name). A research group captured and measured the characteristics of every bird on one of the islands. They also recorded the feeding habits. During their research a drought occured on the island. As a consequence, there were two main food sources, softer seeds and tougher seeds. As a result, the finches split into two main groups. One group had larger beaks and ate the tougher seeds and the other group had smaller beaks and ate the smaller, softer seeds. Interbreeding between the groups was common place before the drought, but was rare during the drought. For this reason this was considered the start of a speciation event, the isolation of gene pools as a function of beak size and natural selection. (To all: it's been a while since I read up on this so feel free to make corrections).A more difficult scenario is geographic isolation. It is very rare for a species to be totally split into two geographic areas. There is usually a small corridor that connects the two. It is in this corridor that one can observe whether or not interbreeding occurs. Then the question of ring species comes into play, which we can get into later after we all have a firm understanding of the scientific definition of species.

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I was thinking that geographical isolation has nothing to do with it. You got a bunch of deer over here in the Northwest and another bunch of the same deer in the Northeast, and they never get together. Nonetheless they are the same species. (later, of course, much later, this situation might change--they evolve differently).

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Mangy Tiger stated about the same as well. You are both correct. They would be separate species if they were given the chance to breed in the wild but chose not too. This would rule out geographic isolation as a de facto criteria for determining species. As you mentioned above, geographic isolation may lead to speciation but is not speciation in and of itself.What would be interesting is if there was a small corridor that linked Eastern and Western deer populations. It is quite possible that these two areas used to meet in the Great Plains which has since been taken over by agriculture. There is still the possibility that there is a northern corridor through Canada. I'm not sure what the real situation is but it might be worth digging into.

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As regards physical compatibility, I suppose you mean something like big dog/little dog. But they are the same species.

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Dogs are a ring species, at least in my opinion. A St. Bernard can not mate with a chihuahua, but there are intermediates through which they can be linked. For instance, a huge dog breed can mate with a large dog breed; a large dog breed can mate with a medium dog breed; medium to small; and then small to miniature. So we are able to move some St. Bernard genes into the chihuahua gene pool, but it is diluted by the time it gets there. Also, when the St. Bernard genes arrive in the chihuahua population it is not able to return directly back to the St. Bernard. There are examples of this type of speciation within nature as well that involves geographic rings, such as a series of subspecies that wrap around a mountain range. While dogs are not separate species it is accurate to state that they are in the process of speciation, even if it is through artificial means.

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I don't understand why DNA incompatibility would not be the deciding factor.

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Because individuals do not pick mates through DNA incompatibility. Gene pools are not kept separate strictly through DNA incompatibility. Take the apple maggot fly (Rhagoletis pomonella). From Observed Instances of Speciation : In this case the flies mate at different times when they used to all mate at the same time. They are still able to hybridize in the lab, but in the wild this does not occur because of the timing. For this reason they are cautiously considered an example of speciation.