quote:One disclaimer is this; I am not saying that all of the evidence, in no way shows anything that might be considered part of an evolution. I actually think a bird with dinosaur features is the type of evidence you might expect had they evolved from them. Not that I would affirm the consequent, I just think the evidence is better explained as the relatively few transitions actually being chimeras, which seems far more parsimonious than assuming the other 99.999999999999% conspicuously absent transitionals, had to exist at some time.
I have said this several times, but it looks as if I shall have to repeat it.
We all know that all life comes from life (and usually from life of the same kind), that every living thing (including ourselves) has parents, grandparents, great-grandparents, great-great-grandparents, and so on in an unbroken lineage that extends indefinitely far back into the geological past, through the Pleistocene, Pliocene, Miocene, Oligocene, etc.
Scientists haven't found fossils belonging to the genus Homo in Lower Pliocene and Miocene rocks, but they have found fossil apes, for example Australopithecus, Ardipithecus, Ouranoptihecus and Kenyapithecus. These apes are, of course, classified, like us, as Primates. Since we must have had Early Pliocene and Miocene ancestors, it seems reasonable to suppose that these ancestors belonged to the same order and family as ourselves (i.e. that they were primates and hominids) rather than that they were, for example, cattle, or whales, or lizards, or fish, or that humans originated by spontaneous generation from dirt.
To summarise this argument, we must have had ancestors that lived in the geological past, and the most likely, perhaps even the only, fossil candidates for these ancestors are apes such as Australopithecus and Ardipithecus.
Can you, or anybody else, either refute this argument, for example by identifying other fossil candidates for human ancestry, or by showing that living things can come into existence without having parents? Alternatively, is there anybody who is wiling to say that this argument is valid, and that I am not talking utter nonsense?
I can understand the appeal of this argument, but let's also note that it has an important limitation. The sword you use is just as sharp against abiogenesis as it is against creationism. If we are going to require evidence before accepting one, then we need evidence for the other.
Creationist invoke a miracle to explain the beginning of live, while scientist invoke abiogenesis which requires a chain leading from chemistry on basic molecules to self-replicating molecules then to life. Neither side can claim that their required process has been observed.
I wasn't discussing the origin of life; I was discussing human evolution from putative ancestors such as Australopithecus and Ardipithecus, which was the subject of the OP. If one rejects the fossil hominids mentioned by Mike's link, then so far as I can see, either humans (members of the genus Homo) must have evolved from other ancestors (either primates or non-primates) or the first humans must have come into existence without parents. Which of these possibilities does Mike prefer?
As you say, the sword that I am using may be just as sharp against abiogenesis as it is against creationism, but I do not think that it is as sharp against evolution. We know where individual living things come from, and we know how small changes accumulate over many generations to produce new species. The fact that living things have ancestors is actually an argument in favour of evolution, even though it may be an argument against abiogenesis.
It isn't that easy to do. Currently, we can create self-replicating, auto-catalysing, homochiral molecules that evolve.
Are they "living." Is a virus "alive"?
I think that this is getting unnecessarily complicated. This thread is supposed to be about 'so called human evolution', not about defining life or about the origin of life.
You are making an invalid, post hoc ergo propter hoc assumption: That because all the life we currently see is the product of a reproductive process of another living thing, that means that life necessarily comes from other living things.
Well, unless you are going to say that life has always existed, that necessarily isn't true. Even if you are going to invoke magic to zap-poof life into existence, that requires that at some point in time, there wasn't any life and after that point, there was and thus, life does not need to come from living things.
But that said, we can't even make the claim that "life comes from life" because casual examination of life shows that it actually comes from non-life: You eat things, break them down into non-living components, and then engage in chemical reactions that incorporate them into the living thing. Remember, you started life as a single cell. You now have trillions of cells. They didn't magically appear and they aren't accumulations of other living things. They were created because that cell took in non-living material and converted it into other cells.
So clearly, there is a chemical pathway by which non-living material can be turned into living material.
Unless you're going to say that there's some magic in that old cell wall they found. For when they placed it around the nucleus, it began to dance around.
But back to my point: The fact that life as we know it now comes from reproductive processes of other living things doesn't mean that life necessarily requires it. It may simply be that it's much easier to make new life once you have some than if you're starting from scratch.
Take the creation of water, for example. Suppose you have two moles of hydrogen gas and one mole of oxygen gas. You mix them at STP. You're not going to get any water out of it because there isn't enough reaction energy to start a reaction.
But once you do spark the mixture, you get a huge reaction...much more than the energy of the spark that got it started. That's because the energy released from one set of molecules reacting is sufficient to get another set of molecules reacting which then cascades throughout the mixture. If you had a huge volume of such a mixture such that the reaction could be sustained for a significant time, then you might conclude that in order to create water, you need to have a reaction of water nearby. After all, all the water that we see is the result of a previous water reaction. We never see water coming into existence in an area where there wasn't a water reaction going on.
But that's not because it can't be done. It's simply because it's easier to get hydrogen and oxygen to react if they're next to a reaction. At the beginning, it was a different chemical reaction that started it which then found a much easier pathway to continue.
We don't know how life got started. We have some intriguing suggestions that evolution is showing us and our knowledge of biochemistry is pointing in, but we don't really know.
But just because life today always seems to use a biological process to produce new life doesn't mean that's the only way.
All this is true, but I think that you are missing the point of the thread and of my reply to Mike the wiz.
In the OP, Mike (or rather his link) mentioned some Pliocene and Pleistocene fossil hominids that have been proposed as ancestors of Homo sapiens and said that none of them had been proved to be human ancestors. His argument appears to be that if we cannot prove that Homo erectus, Homo habilis, Australopithecus africanus, Australopithecus afarensis, Ardipithecus, Orrorin, Sahelanthropus, etc. were our ancestors, then we have no grounds for thinking that we actually had ancestors.
My argument was that we must have had Pleistocene, Pliocene, Miocene, etc. ancestors, and that if the fossils that we know of weren't our ancestors then there must be as yet undiscovered fossil hominids that were our ancestors. You appear to be raising the alternative possibility that Homo sapiens originated directly from non-living organic or inorganic matter by some sort of spontaneous generation, without evolutionary ancestors. Do you actually believe that this is possible, or is this merely a jeu d'esprit, or have I simply misunderstood you?
Like your example of Australopithecus being a transitional or intermediate is very convincing. But many conclude that it is just a species of ape and that not enough bones were recovered to conclude it to be human. No hand or feet bones, only tiny fragments of skull and a few other bones. In engineering we cannot make any assumptions for the consequences could be catastrophically fatal to thousands. Nothing is released before being totally confirmed of its safety and functionality. Australopithecus is a guess isn't it? One opinion vs another.
You show me a series of skulls claiming it to show evolution. You are effectively asking me now for the same thing religion asks... Faith. You are asking me to have faith in your word that these specimens are in fact links in the evolution of man. Can you see how that is not acceptable for myself? Why I must question everything and not just go along with it all.
There is a very simple argument for evolution. It is the obvious fact that every living thing has parents, grandparents, great-grandparents, and so on in an unbroken chain of ancestors extending indefinitely far back in time. Thus, for example, gorillas must have had Miocene, Oligocene and earlier ancestors; tyrannosaurs must have had Jurassic, Triassic and Paleozoic ancestors, etc. Since there are no fossil gorillas from the Oligocene epoch, or fossil tyrannosaurs from Triassic or Paleozoic rocks, these animals must have descended from ancestors that were not gorillas or tyrannosaurs. The same argument goes for human beings; if the australopithecines were not our ancestors, what animals from their time were our ancestors?
I have presented this argument many times, and nobody has ever refuted it, although I admit that nobody has ever admitted the force of the argument. Would you like to try to refute it?
So by your statement you must agree that the theory cannot be regarded as "Gospel". There may be some supporting evidence but our knowledge of the subject is just not enough to say with 100% certainty that every aspect of our theory is correct.
Scientific theories are not regarded as "Gospel"; they are always subject to modification and correction. (So are interpretations of the Gospels, by the way.) However, one doesn't have to be 100% certain that every aspect of a theory is correct in order for the central parts of the theory to be useful and reliable. Although biologists don't know everything about evolution, it remains a fact that living species change over long periods of time and that if we could meet our ancestors of, say, five million years ago we should call them apes. Astronomers don't know everything about planetary dynamics or stellar dynamics, but that doesn't change the fact that the Earth revolves around the Sun rather than vice versa, and that we can use the theory of celestial mechanics to make accurate predictions of such phenomena as eclipses and the paths of comets.