[quote]Professor X wrote:
danweltmann wrote:
Remz wrote:
DA MAN wrote:
nothing more than a theory
Hence the expression “Theory of Evolution”, which is, unlike creationism, at least based on some facts.
Remz
Evolution is an observable fact; it might have been a theory 100 years ago, not anymore. The theories have to do with how specifically evolution occurred, not whether it happened.
As an analogy, 500 years ago it might have been a theory that the Earth is round. Today, the relevant theories deal with how it got to be round, not whether it is so.
Microevolution is not the same as evolution of cross species. Dinosaurs turning into birds has not been observed and is not proven as fact. That is why the theory that all life came from a single celled organism is still a theory regardless of how much you may wish it wasn’t so.[/quote]
There have been cases of species evolving into others in the last few hundred years, usually plants, I regret not having the examples handy.
On a larger scale, nobody claims to observe macroevolution (I presume that is what you mean by cross species evolution). What is observed are fossils, which tell quite a tale, and in recent years evolutionary trees have been revised on the basis of molecular evidence. Dawkins makes the argument that even in the complete absence of any fossils, today evolution is glaringly obvious, due to the evidence encoded in our genes.
I recomend “The Ancestor’s Tale” by Richard Dawkins, his magnum opus.
The stuff about what I wish it were so was a cheap shot, so I’ll just ignore it.
As for us originating from single celled organisms, the theory (and I admit it is just that) is more generally described as all life having a common ancestor, incidentally one celled. Not necessarily, since life probably began before single celled organisms.
The argument for a common ancestor has nothing to do with fossils, and everything to do with DNA. Imagine base pairs as letters, genes as words, an organism’s entire genome as a book. We all use the same letters, the same way of making the words, the same codons specify the same amino acids, from arcaebacteriae to mushrooms, viruses and elephants.
If you saw a bunch of languages all using the same alphabet, you might be tempted to conclude that at some point in the past there was only one language that used that alphabet (a limited analogy, I admit, since other languages can and do adopt alphabets, an option not open to life).
Considering that millions of amino acids exist in abundance, and that none seem to be particularly better or worse than the 20 or so that all of life uses, it indicates rather strongly a common ancestor at some point in the past.
Interestingly, this argument does not preclude different beginnings for life, it’s just that all life that survives seems to have come from one ancestor.