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Author | Topic: Behold the Homind | |||||||||||||||||||
Chiroptera Inactive Member |
It would appear that the earliest known hominid in our line was bipedal -- she walked upright. This species, Australopithecus afarensis, showed no other characteristics that we would associate as distinguishing humans from the non-human apes.
This site has some interesting data on early hominids and their fossils. It appears that our modern form of H. sapiens appeared perhaps as long as 200,000 years ago. Depending on whether you consider H. heidelbergensis to be a member of our species, our species may actually extend to as far as 500,000 years ago.
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Chiroptera Inactive Member |
We have species A. A small subpopulation of A is isolated from the rest of A, and this subpopulation evolves in species B. Now we have two species existing at the same time. Maybe another subpopulation of A is isolated and evolves into C; now we have three species. A eventually goes exinct, and now we have B and C as two closely related species existing at the same time.
Maybe the isolating features end, and B and C then move into the terroritory formerly occupied by A. Then we even have two related species existing in the same place at the same time. If B and C evolved to occupy slightly different niches, then they wouldn't directly compete, and so they may be able to coexist for a long time. Edited to add:It doesn't matter whether or not you are a Biblical creationist or not, ausar_maat; it is a good question, and even some of those who accept the theory of evolution may not be aware of possible answers to this. This message has been edited by Chiroptera, 04-Oct-2005 05:33 PM "Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt
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Chiroptera Inactive Member |
quote: Species do not evolve because there is a "need". In any population, the individuals vary in their physical characterists. Some physical characteristics make it more likely for an individual to survive or to mate (and thus pass on these characteristics to its offspring), some make it less likely that an individual will survive or mate, and thus it characteristics will not be passed to the next generation. So the next generation will have slightly more individuals with the "good" characteristic, and slightly fewer individuals with the "bad" characteristic. There is no teleology here -- if you look at all the coyotes that live in a certain area, each one will be slightly different that any of the others, and perhaps these slight differences will allow one a better chance to avoid a predator, catch prey, or find a mate than another individual. -
quote: So a pre-giraffe with a slightly longer neck could reach food that a pre-giraffe with a shorter neck cannot. So a longer necked pre-giraffe can not only survive in dense forests where there is plenty of underbrush, but can range into more open grassland, where it can reach the leaves of short trees and the bottom leaves of slightly taller trees. A shorter necked individual is pretty much stuck in the forest, where there might be more competition for other individuals -- the longer necked individual can find food that no one else can reach, so it is less likely to go hungry. Thus, in the next generation, there are fewer short-necked pre-giraffes and more long-necked giraffes. -
quote: Primates are social animals. They live in groups and act cooperative. Often, there are hierarchies among the individuals. Those in the upper levels in the hierarchies are more likely to get first dibs on available food as well as have more access to mates. A slightly more intelligent ape will be better able to keep track of alliances and perhaps figure out the consequences of its actions in regard to the reactions of the others in the tribe. So a "smarter" individual is more likely to produce offspring than a "dumb" one. (Eventually, of course, we get a positive feed back case where a smart individual is more likely to able to make long term plans, make tools, and use more sophisticated communication). -
quote: Like dolphins (which, incidently, are also social species)? At any rate, intelligence is not an automatic advantage to the one that possesses it. Higher intelligence requires a larger brain, which then requires more energy, energy that cannot be used to run faster, climb higher, or breed more often. Also, why would intelligence be an advantage to, say, aardvarks? It wouldn't: all anthills are pretty much the same, the same techniques will always suffice to get into them, aardvarks do not have hands so tools would be unavailable to them -- pure instinct will suffice for the relatively simple aardvark world, so more intelligent aardvarks would not necessarily replace less intelligent ones. The question is not "why aren't all species, or all species of apes, intellgent?" The question is, "why did intelligence prove to be advantageous to human ancestors?" And we may never know the answer to that. If we suppose that natural selection is the main driving force of evolution, then all we can say is that a population of our pre-Australopithecine ancestors were in an environment that larger brains and more intelligent gave the individuals with those traits an advantage over the others. Quite possibly, in that environment there would have been a number of different traits that would have been advantageous; however, since mutations are random, it was the mutations that led to greater intelligence that appeared first, and so this is the direction that our species took. "Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt
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Chiroptera Inactive Member |
Hello, ausar_maat.
I am a bit confused. I thought I already answered each of these questions in my previous post. Was I unclear? Do you disagree with what I said?
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Chiroptera Inactive Member |
Then let me quote what I felt is the key sentence in my post:
And we may never know the answer to that. If we suppose that natural selection is the main driving force of evolution, then all we can say is that a population of our pre-Australopithecine ancestors were in an environment that larger brains and more intelligent gave the individuals with those traits an advantage over the others. Have you ever played pachinko? What does one ball take on path from top to bottom, and another ball take quite a different path? Both paths are completely determined by Newton's Laws of motion, and yet you will have a difficult time explaining exactly, in detail, why one ball "choose" to go in one path and another ball "choose" to go in another. In any evolutionary lineage, the exact "path" that lineage takes will depend on the exact environment in which the population lives (and that alone is a lot of variables!), the physical anatomy of the species (which may preclude some traits from being advantageous), the niche in which the species lives, and which mutations actually occur at which times. That is a lot of variables; it really shouldn't be a surprise that different populations of a species will travel down different evolutionary paths. As far as your example of a "leaf insect", Thor correctly points out that your question assumes too much teleology. There was a population of a certain species of insect. In that population, some inidividuals that looked a little more leaf-like were able to leave more offspring than individuals that looked less leaf-like. After many generations, you have a species of insect that looks a lot like a leaf. "Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt
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Chiroptera Inactive Member |
quote: Boy, that is an ancient term that is no longer used! Where are you getting your information? If your sources are this out of date, no longer you are confused! "Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt
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Chiroptera Inactive Member |
Well then, why don't you go to a library and check out a more recent book on evolution? There are a lot to choose from. I bet people here have their favorites. My favorites are the earlier collections of essays by Stephen Jay Gould (like The Panda's Thumb).
Are you still in high school? Or college? Take a biology class. That might be informative, too. But your knowledge of evolution is out-dated material that still calls the Australopithecines by the name Zinjanthropus, then I'm not sure that a few posts on a message board will be very enlightening. Another good source is Talk Origins. They have a few basic pages and FAQs that might be enlightening as well. "Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt
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Chiroptera Inactive Member |
Heh. That would explain a lot, wouldn't it?
Thanks for the compliment. "Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt
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