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4: Paleontology

[ "article:topic-guide", "Paleontology", "authorname:aschoenberg" ]
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  • Paleontology is the old life forms. Now that we've introduced a few basic concepts in biology, we are going to start mapping our family tree. With genetics we've seen that all life shares DNA, that the origin of life is this molecule and it's ability to direct the activities of the individual, to accumulate changes, and to copy itself. With DNA at the base of our tree, we'll continue to trace the branches and connect them to our own family.

    • 4.1: Paleontology → Paleoanthropology → Archaeology → History
      Paleontology looks at life in the past, and the most popular branch is dinosaurs. Closely related human ancestors get their own subfield, paleoanthropology, and the dividing line paleontology and paleoanthropology is usually when they start walking on two feet. Confirmed human ancestors get another field called archaeology, and the line between paleoanthropology and archaeology is usually set at anatomically modern Homo sapiens. History starts with written records.
    • 4.2: Macroevolution
      Another word for macroevolution is speciation, the production of species, this is the level of evolution that Darwin studied, the kind that occurs over immense periods of time, where small changes accumulate to make life diverge into often drastically different forms. Now that we've introduced Mendel and cellular biology we can explain the two main pieces that Darwin was missing, heredity and variation.
    • 4.3: Species vs. Paleospecies
      In the next section on paleoanthropology, we will lump fossils into groups and label them with an official looking genus and species designation written in Latin and in italics, but it's really important for you to remember that this designation is not a concrete fact, it's just a hypothesis that will continue to be tested (and often contested). Understanding that paleospecies are hypotheses will help you to understand the context for many of the debates in paleontology and paleoanthropology.
    • 4.4: Interspecific vs. Intraspecific Variation
      When you lump a bunch of fossils together and call them a paleospecies, you are saying that all the differences between the fossils are intraspecific variation, variations within a species. If you split all the different looking fossils into separate species then you are seeing interspecific variation, variation between species; intra- means "among" and inter- means "between"
    • 4.5: Plate Tectonics
      Plate tectonics can cause macroevolution. If a species roams over a continent and that continent splits into two, the evolutionary force of migration is prevented, and the two population will accumulate variations over time until they eventually become separate species.
    • 4.6: Adaptive Radiation
      When giving the opportunity, a group of species will move into available ecological niches. A classic example is around 65 millions ago, the mammals took on ecological roles formerly held by dinosaurs.
    • 4.7: Analogy vs. Homology
      The dolphin's fin and the shark's fin are coded for by totally different genes, and have a totally different evolutionary pathway. Traits that look the same but evolved separately are called analogies. Homologies are traits that share a common evolutionary pathway, and the genes that code for them. The range of morphology of vertebrate forelimbs is incredible, but they all have the same genetic source, and thus share most of the same bones.
    • 4.8: Taxonomy
      The two classic lines of evidence have been comparative anatomy and fossils. Recently, genetics has almost completely taken over comparative anatomy research, because it's like going to the primary source, the gene is what codes for the anatomy. It used to be that using fossils was the only way to get dates, but recently, the differences between the mutations in the mitochondrial DNA (mtDNA) of a species can be used to calculate the time when that species split off from another species.
    • 4.9: Human Taxonomy
      The classic Linnaean taxonomy is basically part of your family tree without drawing in all the branches. Linnaeus was great for the 1700s, but can be very misleading today if you try to cram all the different branches of life into arbitrary horizontal categories like: Kingdom, Phylum, Class, Order, Family, etc. All of these categories are arbitrary and the only way to make them work is through lots of "sub-" and "super-".
    • 4.10: Mammals
      There are three main branches of mammals alive today, classified mostly on their reproductive system, monotremes lay eggs, marsupials have pouches, and placental mammals keep the kids inside for longer. Much of what it means to be human is shared with all mammals.

    Thumbnail: Tyrannosaurus rex, Palais de la Découverte, Paris. Image used with permission (CC BY-SA 3.0 David Monniaux).