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6_2 The Early Hominins_lecture script.pdf

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Simon Fraser University
ARCH 131
Dennis Sandgathe

UNIT 6THE EARLIEST HOMININS 62 The Early Hominin Species Slide 1 Nowadays a lot of time is spent by researchers hunting for new fossil hominins especially in Africa although some very old hominin remains are found in Asia and Europe as well Whenever a new fossil is recovered researchers must then try to determine which existing genus and species it might be assigned to or if it is different enough from all previous fossil discoveries if it should be given its own genus and species designation So before we are introduced to the earliest hominins its important that we understand a few important concepts about how researchers go about arranging hominin fossils when new ones are discoveredthis is the task of classifying the hominin fossils that researchers find just like the earliest scientists were doing with rocks plants animals stars and planets etc etc Slide 2 The 2 most basic concepts are Phylogeny and TaxonomyPhylogeny is the actual evolutionary relationship between different organisms Today with DNA analysis establishing the phylogenetic relationships among living species is much easier since presumably the closer two organisms are related the fewer differences there will be in their DNA However when we are dealing with just the skeletal remains of these organismstheir bonesdetermining their actual evolutionary relationship is practically impossible So far we have only been able to recover DNA from the bones of two other hominin species besides us Neandertals and a newly discovered species we will be introduced to later but these are relatively recent skeletons from within the last 100000 years The chances of finding intact DNA in the bones of hominins that date much older than this are likely nonexistent This is especially so for fossil hominins in Africa since heat destroys the integrity of DNA very quickly and well Africa is pretty hot We can however usually get a reasonably good idea of Phylogenetic relationships of early hominins based on specific differences and similarities between their skeletons but realistically unless we are lucky enough to recover DNA from them we will never know for sure how they were related to each other in evolutionary termsWeve already been introduced to the term Taxonomy This is the process of classifying organisms based on our best understanding of their phylogenyessentially trying to reconstruct their family trees Because we have not been able to recover DNA from most ancient hominins then the process of trying to develop taxonomies for the fossils we have recovered so far is a very difficult and contentious undertaking and disagreements are very common However disagreement is a very healthy and desirable component of all scientific research When we are dealing with such incomplete data sets like we are with fossil hominins if there were no disagreement between researchers then we should be worried because it would be an indication that there was something wrong with how the science was being practiced Slide 3 When it comes to attempting to make sense of the various hominid fossils that researchers have recovered there are 2 main approaches to trying to determine their evolutionary relationshipsto construct as accurate a family tree as possibleThe more traditional approach is called Evolutionary Systematics With Evolutionary Systematics a researcher weighs all the available evidence that can be brought to bear on the issue including the comparative morphology of the different hominins in question the relative ages of the different skeletons and the geographical evidencewhere do the different hominids remains come from What sort of environment did they live in All these data are then used to try to reconstruct the most parsimonious explanation for past evolutionary relationships
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