As for the lack of transitional species......it is well known that the fossil record displays taxonomic, geographical and temporal bias. Not every organism that ever lived has the materials to fossilize properly. Not all areas of the globe have been explored, and with events such as the shifting of plate may fossils may have been destroyed.
I'm not a biology major but I do remember this from an anthropology class in college. Evolution does't happen overnight. When a mutation occurs, it's usually subtle... i.e., webbed feet for humans. The species branches when a group is separated. Eventually, over hundreds of thousands of years, due to natural section, the is DNA becomes incompatible with the old group. Those in the group with old DNA die off. Since humans only branched off 10 of thousands of years, there's not enough time for a species separation but you can tell just by looking at skin pigmentation, eye color etc, that mutation was going on within the isolated groups of humans (according to their environment)... If we were giving a few more hundreds of thousands of years of racial isolation, we would probably become separate species. As for the fish question. You're trying to hard to justify your own belief. Otherwise... really???
I should not that contemporary humans are not longer bound by the same natural selection process so we'll probably never branch off to different species. "Non-practical" traits; diabetics, obesity, etc... will perpetuate unless something major happens.
About diabetes (Type 1, not Type 2) you should read Survival of the Sickest by Dr. Sharon. It's pretty fascinating stuff.
I think Otto mentioned domestication at one point. There's a case that we're becoming more infantilized as technology picks up the heavy lifting in our daily struggles with nature.
I get dumber as this thread gets longer. http://www.flickr.com/photos/ethanhein/3420191462/sizes/o/in/pool-1017440@N25/ I love this picture. Too big to post, but it really puts it in perspective how LONG it took for sea creature to become land ones and how little time we've been on earth.
Cool picture. Thanks for posting. I think one conceptual hurdle people have with evolution is just the time-scale we're dealing with. We tend to think that humans have been around for a long, long time, and what came before humans was of a comparable time-scale. Thinking about it in that way, it is unbelievable how a complex organism such as ourselves could come about "randomly". But life has been evolving for billions of years. Humans capable of reflecting on the wonders of this process have just recently come into existence. One analogy that Carl Sagan uses is that if we take the time in which life has been evolving to be 1 year, humans started appearing only in the last 30 seconds of the calendar.
We really do have a tough time with the vastness of space and time. It's not what we're used to or what we see in our day to day (not epoch to epoch) lives. A long time to us might be a decade or two based on our experiences. A long distance is Houston to Los Angeles, especially if you drive it. Flying is cheating since you don't experience the distance with any frame of reference. The best analogy I ever heard was when I saw Stephen J. Gould speak at UCLA many years ago (and I think he borrowed it from elsewhere if memory serves). He said that if you hold your arm outstretched to your side and your nose represents the time that the earth was formed a single stroke of a nail file on the middle finger would wipe out all of human history. It's tough to wrap your mind around that sort of thing, so trying to cope with the idea of changes over billions of years is just not something most people are readily equipped to handle conceptually. It tends to lead to people arguing from incredulity, as seen in most of the OPs posts, really.
After reading through some of this thread, in answer to the OP's original question, the answer is: you don't want to understand evolution.
All present-day life arose from a single ancestor Protein analysis rules out multiple sources By Tina Hesman Saey Web edition : Wednesday, May 12th, 2010 http://www.sciencenews.org/view/gen...l_present-day_life_arose_from_a_single_origin A new study uses statistics to test whether life on Earth can be traced back to a common ancestor (example shown in a) or multiple primordial life forms (b). Dotted lines indicate gene swapping between species. M. Steel and D. Penny/Nature 2010 One isn’t such a lonely number. All life on Earth shares a single common ancestor, a new statistical analysis confirms. The idea that life-forms share a common ancestor is “a central pillar of evolutionary theory,” says Douglas Theobald, a biochemist at Brandeis University in Waltham, Mass. “But recently there has been some mumbling, especially from microbiologists, that it may not be so cut-and-dried.” Because microorganisms of different species often swap genes, some scientists have proposed that multiple primordial life forms could have tossed their genetic material into life’s mix, creating a web, rather than a tree of life. To determine which hypothesis is more likely correct, Theobald put various evolutionary ancestry models through rigorous statistical tests. The results, published in the May 13 Nature, come down overwhelmingly on the side of a single ancestor. A universal common ancestor is at least 102,860 times more probable than having multiple ancestors, Theobald calculates. No one has previously put this aspect of evolution through such a stringent test, says David Penny, a theoretical biologist and Allan Wilson Centre researcher at Massey University in Palmerston North, New Zealand. “In one sense, we are not surprised at the answer, but we are very pleased that the unity of life passed a formal test,” he says. He and Mike Steel of the University of Canterbury in Christchurch, New Zealand, wrote a commentary on the study that appears in the same issue of Nature. For his analysis, Theobald selected 23 proteins that are found across the taxonomic spectrum but have structures that differ from one species to another. He looked at those proteins in 12 species — four each from the bacterial, archaeal and eukaryotic domains of life. Then he performed computer simulations to evaluate how likely various evolutionary scenarios were to produce the observed array of proteins. Theobald found that scenarios featuring a universal common ancestor won hands down against even the best-performing multi-ancestor models. “The universal common ancestor (models) didn’t just explain the data better, they were also the simplest, so they won on both counts,” Theobald says. A model that had a single common ancestor and allowed for some gene swapping among species was even better than a simple tree of life. Such a scenario is 103,489 times more probable than the best multi-ancestor model, Theobald found. That’s a 1 with 3,489 zeros after it. Theobald’s study does not address how many times life may have arisen on Earth. Life could have originated many times, but the study suggests that only one of those primordial events yielded the array of organisms living today. “It doesn’t tell you where the deep ancestor was,” Penny says. “But what it does say is that there was one common ancestor among all those little beasties.” A new study uses statistics to test whether life on Earth can be traced back to a common ancestor (example shown in a) or multiple primordial life forms (b). Dotted lines indicate gene swapping between species. --- By the way here is the probability: 1 to 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
