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Fossil Record "Taking into account all of these requirements, it's clear that the fossil record must be incomplete. How incomplete? The total number of species that ever lived on earth has been estimated to range between 17 million (probably a drastic underestimate given that at least 10 million species are alive today) and 4 billion. Since we have discovered around 250,000 different fossil species, we can estimate that we have fossil evidence of only 0.1 percent to 1 percent of all species - hardly a good sample of the history of life! Many amazing creatures must have existed that are forever lost to us. nevertheless, we have enough fossils to give us a good idea of how evolution proceeded, and to discern how major groups split off from one another." (Why Evolution is True, P. 22) From Fish to Amphibians: One of the greatest fulfilled predications of evolutionary biology is the discovery in 2004, of a true transitional fossil form between fish and amphibians. Transitional fossils are the fossilized remains of intermediary forms of life that illustrate an evolutionary transition. They are sometimes referred to as a "missing link" fossils. This particular fossil species is Tikaalik roseae, a fossil which tells us a lot about how vertebrates came to live on land. "Why Evolution is True" - Jerry Coyne, 2009, p.35 http://tiktaalik.uchicago.edu/ http://en.wikipedia.org/wiki/Tiktaalik Definition of transitional fossils from Wikipedia - http://en.wikipedia.org/wiki/Transitional_fossil Tikaalik roseae is a intermediary form between fish and modern amphibians. Prior to the 21st century, there was no good representative of something that showed intermediary fin development. Paleontoligist Neil Shubin, looking at the fossil record, determined that there should be a good representative form in between fish and amphibians. He then decided on the appropriate sedimentary layer it should be found in, and after years of research actually found the exact representative (several of them) in Canada. This discover was written up, published, and finally made into a bestselling book, "Your Inner Fish." Like a fish, Tikaalik roseae has gills, scales, and fins. However, like an amphibian, it also has a flattened head like a salamander with eyes and nostrils on top rather than the sides of the skull. it also had fins that were decidedly more robust to help it push itself on land. And perhaps more importantly, it has a neck. Fish don't have necks - their skulls join directly to their shoulders. (Why Evolution is True, p. 37). Good scientific theories should have a high degree of predictability. In this case, a species was predicted, and then found - confirming the evolutionary process. There are many confirmed transitional-type fossil species within several families (whales and horses for example). If fossil evidence of evolution were not true, fossils would not occur in an order that makes evolutionary sense. Transitional Fossils Transitional fossils are the fossilized remains of intermediary forms of life that illustrate an evolutionary transition. "Missing link" is a popular term for transitional forms. Numerous examples exist, including those of primates and early humans. According to modern evolutionary theory, all populations of organisms are in transition. Therefore, a "transitional form" is a human construct of a selected form that vividly represents a particular evolutionary stage, as recognized in hindsight. Contemporary "transitional" forms may be called "living fossils", but on a cladogram representing the historical divergences of life-forms, a "transitional fossil" will represent an organism at the point where individual lineages (clades) diverge. (Wikipedia) The most recent transitional fossil was discovered in 2004, Tikaalik roseae, an intermediary form between fish and amphibians. This fossil discover is the subject of the book, "Your Inner Fish", by Neil Shubin - a fish paleontologist. http://www.amazon.com/exec/obidos/ASIN/0375424474/bookstorenow30-20 A more thorough discussion of transitional fossils can be found the talkorigins website - a website dealing with mainstream scientific essays on evolution. http://www.talkorigins.org/faqs/faq-transitional/part1a.html#intro Evolutionary theory predicts that many animals and plants arriving in new and unoccupied habitats will evolve to thrive there, and will form new species, filling up ecological niches. And they will usually find their relatives on the nearest island or mainland. Species - Groups of interbreeding natural populations that are reproductively isolated from one another. They don't exchange genes, and the constitute distinct gene pools. Races - Races don't show all-or-none differences in the forms of genes (alleles) that they carry. Instead, they usually have the same alleles, but in different frequencies. The ABO blood group gene, for example, can be found in all humans but they may have different frequencies in different races. Species are most likely created by habitat isolation - this may include segregation of land masses (islands), glacier isolation, desert formation, mountain uplift, etc. This may not just happen with animals as much as it happens with animal food sources. In other words, the barriers are merely the by-products of natural or sexual selection that cause geographically isolated populations to evolve in different directions. Species can easily be created by species dispersal. Birds may fly to a different island to colonize it. That island begins to go through a long, slow period of drought, the plant life changes, the birds adapt to their new food source on the island and they no longer feed on their original mainland food, beaks change ( and perhaps voice, mating rituals, and plumage) then they no longer interbreed with the original mainland birds. New species. Creationists often claim that if we can't see a new species evolve during our lifetime, then speciation doesn't occur. But this argument is has holes. It's like saying that because we haven't seen a single star go through its complete life cycle, stars don't evolve. Or because we haven't seen a new language arise, languages don't evolve. Speciation occurs when two (or more possibly) subsets of a formerly interbreeding population become reproductively isolated. For many years, speciation theorists thought that virtually all speciation occurred when the two subsets of the population where separated by geographical boundaries. (i.e., the species became split by a river, mountain range or a small group migrated out of the main region inhabited by the species.) Reproductive isolation followed physical isolation as the two, now separate lineages, diverged. This could occur for many reasons, for example mating rituals grew different or chromosome numbers changed etc. etc. In any case the end result would be that the two lineages could no longer interbreed if they encountered each other. (Incidentally this type of speciation is called allopatric speciation). (talkorigins.com)
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