There are two types of changes commonly referred to by the term "evolution". One is "micro-evolution" - change within a species, and the other is "macro-evolution" - change that results in a new species.
We see all kinds of examples of "micro-evolution" around us constantly. Examples are the various breeds of dogs, cats, horses etcetera. Although a great dane is physically substantially different from a chihauha, they are both "dogs" and, though difficult, capable of interbreeding to possibly produce third breed of dog. Also, as segments of an established species move about geographically, charactersitics that enhance it's survival become more promenant, such as long hair in colder climates and shorter hair in warmer climates. This produces a wide, but limited variation of characteristics within a species (Mendell's Law), but not new species.
However, we can not breed a cat and a dog to produce a "cog", "cag","dat" or a "dot". The reason, we have learned in the last 30 odd years, is because of differences in their DNA. A single pair difference in the length of a multi-milliion-pair DNA molecule, like a zipper missing a tooth, can prevent a successful replication.
The only tool available for "macro-evolution" to work is "mutation", the adding or removing of DNA information. In the natural world (outside of the lab), this is a totally random occurance. The problem is that except in the case of single celled organisms, assuming, by some chance, that an entire organism is mutated (a phenominally improbable task in itself), there would have to exist another organism that has been mutated EXACTLY in the same manner and in close enough proximaty for them to mate and reproduce, or the new species would die off in it's first generation.
As far as life on Earth coming about sponaniously from the "primordial slime" (biogenesis), one must consider it's extreme improbability from a mathematical standpoint, as well as conflicting conditions required for life to begin and continue in earths atomsphere, even millions of years ago (the Miller-Urey controversy).
Scientists consider odds of 1 in 10 to the 50th (1 followed by 50 zeros) to be "statistically impossible". Mathematician Emile Borel calculated the odds of randomly assembling a 100-amino-acid-string, under perfect conditions, to be 1 in 10 to the 125th. He also calculated the odds of producing a 227-amino-acid-string (the smallest known string for a living organism) at 1 in 10 to the 119,000th. This does not include any of the machinery necessary for replication and cell function.
Based on these points, I consider "macro-evolution", "Darwinian evolution", "neo-Darwinian evolution", "punctuated equalibrium" and even "theistic evolution" to be scientifically defunct.
Next, one must consider the geologic and fossil evidence. The fossil record indicates a sudden explosion of fully-formed complexed life, with all known species appearing at once (the Cambrian Explosion). We have evidence of certain species becoming extinct, but no new species being generated.
I believe that all of the evidence, when considered as a whole, points to an "Intelligent Designer".
The commonality of organisms (the knee example) point to a "common designer" rather than to a common ancestor, in a similar manner that a hammer might resemble a mallet or a sledge, parts of a car might resemble similar parts on a baby carrage or a jet airliner.
Son-cerely,
Nate