there used to be all different kinds of animals in the “homo” (can the lame jokes) genus, what happened to them all, why did we suceed, while they died out? other genus’ (geni?) have many speces in their group, why don’t we?
Actually, they don’t. There are 1 maybe 2 species in Pan ( chimps, arguement over whether "pygmy’ or bonobo chimps are species or sub), 1 maybe 2 gorillas, etc, etc. It appears now we absorbed Neanderthal man (which does explain certain individuals you see hanging around street corners), and most of the others evolved into us. Usually there was 1 or 2 species of “Homo” at any one time. Now there is one. There has been arguments tht some of the “races” are actually subspecies, but that is no longer politicaly correct. Even if there WAS a “clear case” of a sub species of ol’ HS, we would probably ignore it, for the sake of being PC.
no, i didn’t mean why are we the only ones who are alone in a genus, i meant, why are we alone in our genus?
as far as a sub-species’ go, I for one wouldn’t ignore it.
another semi-related Q (hey, it’s my post, i can hijack it): what defines a species? why aren’t the chiuhaha (sp?) and the great dane considered different enough? how much genetic seperation does there have to be?
i’m off to bed now (feels good to say that.)
The way I understand it, if two beings can produce fertile offspring together, then they belong to the same species.
All dogs belong to Canis domesticus. Different breeds of dogs are just different races like people. The same species name (domesticus in a dogs case, sapiens in our case) means that individuals are capable of producing offspring. As for having no other “Homo”, I asked an animal behaviorist, and he said that we’re a warring species and we probably managed to kill the rest off before they had time to flourish.
I think they now add “and do so under natural conditions.” There was some problem with some degenerate lion and tiger in captivity producing fertile offspring. They either had to call lions and tigers conspecific or change the definition. Even so, they seem to fudge a bit. My birders’ guide has several examples of different species that produce hybrids. That should make them the same species, but for some reason it doesn’t.
Not only must they produce offspring but the offspring must be fertile too.
By the time modern Homo sapiens appeared, there was only one other hominid species: Homo neandertal.
Homo sapiens coexisted with Homo neandertal for over 50,000 years in Europe. There are H. sapiens archaeological sites within a few miles (and in the same time period) as H. neandertal sites, and there’s no fossil evidence they ever fought each other.
We don’t know why the Neandertals died out, but indisputably they did “flourish.” They lived for tens of thousands of years, a good run for any species, and their demise could have been completely unrelated to competition from H. sapiens. It’s just as likely they died out simply because the environment changed quicker than they could adapt. There’s a good book about these issues called “The Neandertal Enigma,” by James Shreeve.
It’s probably just an accident of natural history that humans are the only hominids alive today. Further back in the archaeological record, we find periods where several hominid species did coexist. It’s assuming a lot to say they must have fought each other. The evidence isn’t there.
"All dogs belong to Canis domesticus. "
Small nit to pick. Dogs are Canis Familiaris.
John
The definition of species is pretty arbitrary, actually. Theoretically, it’s the interbreeding thing, but there’s plenty of odd cases and exceptions. While a St. Bernard and a chihuaha may(?) be genetically interfertile, for instance, I doubt that they’d be physically capable of mating. Of course, a chihuaha could mate with a Jack Russel, which could in turn mate with a beagle, which could mate with a German shepherd (don’t laugh, that’s what we think my mom’s dog is), and the shepherd could then mate with a St. Bernard. Where in that progression do you draw the dividing line?
Another dog example: Dogs (C. familiaris) and wolves (C. lupus) are generally considered different species, but dogs and wolves can interbreed to produce fertile offspring, and do so, given the opportunity.
There’s other problems, too: How do you decide if two populations separated in time are a distinct species (some of our ancestors come to mind)? What about species that reproduce asexually? A dandelion can’t “mate” with anything, is each individual plant its own species?
To expand on what Chronos said: the definition of genus is probably even more arbitrary than the definition of species.
If Gorillas, chimpanzees, orangutans, siamangs, gibbons and humans were insects (for example) with the same degree of differentiation, they would very probably be in the same genus. Since we’re talking about ourselves we attach a lot more importance to the subject and keep our species apart from all others.
Not to nit-pick again, but most modern taxonomies call dogs Canis lupus familiaris, a subspecies of Canis lupus (wild wolves). Domestic dogs and wild wolves can (and do) interbreed with little or no difficulty, even in “natural” settings, and produce fertile offspring.
The problem we run into with taxonomy is that “nature” doesn’t classify, we do. Nature does what nature does, and as soon as we try to come up with a convenient definition of what a “species” is or what a “genus” is, nature shows us exceptions. Of course, it is convenient to have some system to classify by rather than saying “Yup. There’s a lot of stuff out there.” But we must realize that the description is not the thing, regardless of what the thing is. Nature does what nature does folks. Any classification system or set of definitions we attempt to put on it is BOUND to be flawed. It can’t be avoided.
As is clear from the thread, classifications like species and genus are pretty arbitrary and open to reexamination. Along the lines of the dog example, there’s a “species” of frog on the US East Coast from about NC to GA. Individuals can breed with neighbors all along the coast, but GA individuals can’t breed with NC individuals. Again, where do you draw the line? There are lots of examples like this in any college evolution or biology textbook.
Some people still want to call Neandertals a subspecies of H. sapiens, though that’s becoming less and less popular. It is clear that modern humans and Neandertals coexisted, apparently peacefully, for thousands (I think?) of years - a long time, anyway. Whether they were absorbed or outcompeted and driven to extinction is still up for debated, though I think the absorption theory is winning at the moment.
When you think about it, the interbreedability (new word! It’s mine!) definition of species is pretty hard to justify. I mean, if you really wanted to be scientific about it, you’d have to get all the males and all the females and see who can successfully reproduce with who. Problems ensue. Ah, well. Blame Linnaeus. It’ll do until something better comes along.
remember killer bees? they are a hybrid of african and europeian bees, yet they are firtile. does that make them the same species?
To keep the ball rolling: Are we Homo sapiens, or homo sapiens sapiens? I’ve heard both. if we’re soposed to be a sub-species, then of what?
Well, a good question, what is a species? depend on who doing the classification. If humans were beetles, there is no doubt that an entologist would list the 4+ races as differnts species. If humans were birds, specialists would list them as subspecies. But as humans are humans, anthropologists say we are all one species, and they are even debating if there is such a thing as 'race".
And, eggo, it is important that we are alone in our genus, and so are most of the other primates. As Arnold mentions, if these were not Apes/simians, they would likely be all one genus.
The new theory now is that we assimilated (by breeding) the neanthertal, and thus they were subspecies.
if that’s the case, then (by the “weather they can produce fertile offspring” classifiaction) Homo Spaiens and neandertals would have had to be the same species to begin with.
Exactly. That’s why Daniel said they were subspecies.
In response to part of the original question, there are many genuses which have only one species in them. Classic taxonomy attempts to lump organisms together by common features, and sometimes there isn’t any other species “close” enough to go into the same genus as a given organism.
Some would claim that the current system of scientific nomenclature is outmoded - cladistics provides a better scheme for representing evolutionary relationships.
I would reccomend Richard Dawkins’ “One True Tree of Life” chapter in either “The Blind Watchmaker” or “The Selfish Gene” (I forget which).
I’m not scientific, but rather an observer. And I’ve noticed that there is MUCH more variation in facial appearance between humans (doppelgangers excluded), than there is, say, between one poodle & another, or between one chihuahua and another, or between one cat & another (disregarding their hair pigmentation). So what do scientists have to say about that?
Well, I can’t say for sure what a biologist would say, but I would say that you are not actually looking closely at the individual animals you have named.
It is similar to the phenomenon where many humans express the idea that all members of a different race “look alike,” particularly when the individual does not have frequent contact with members of the other group. (I am not suggesting that you, personally, are either a racist or a speciesist (specist?). I am pointing out a fairly common psychological characteristic of people.
I cannot identify any of the horses at the barn where my wife currently rides. I only get out there three or four times a year and I have not learned to identify the individual horses. Several years ago, I was more likely to find myself at the barn once every week or more often. At that time, I could name every horse with a quick glance. Now, “they all look alike.”
Similarly, my wife has a couple of snakes and we raise feeder mice. When I find myself doing the feeding and cage cleaning daily for several weeks, I can identify every mouse on sight (I am careful not to name them, but I recognize the individuals). When I have to work late through two or three weeks and my wife does all the chores, the next time I feed them or clean their cages, I find myself looking at a bunch of strange mice.
I would not be surprised that you have the same situation when you attempt to differentiate poodles. They have differences that you are simply not perceiving.