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51 Cards in this Set
- Front
- Back
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Type specimen
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A relatively well-preserved fossil among those found at time of initial discovery
Does not have to be "typical" of the species |
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What is taxonomic analysis (and other forms of analysis) based on?
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Assessment of morphology/phenotype, both metric and nonmetric
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What do researchers need to be careful of when doing metric analysis of fossils?
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To make sure the measurements reflect the size and shape of the fossil before fossilization. Rock matrix getting inside bone can make it bigger, and sandblasting and erosion can make it smaller.
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What is used to help decide how much variation should be tolerated in a single species?
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Closely related living animals, such as African apes or baboon
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Biological species concept
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Ernst Mayr: A species if a group of interbreeding natural populations, reproductively isolated from other such groups
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How can we determine species without information about its mating habits?
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By using information about appearance, structure, and (if it's there), DNA for info about genetic makeup
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What problems occur when trying to determine species in the fossil record?
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-We don't have complete animals in fossil record. Restricted to hard tissue.
-Time. Random variation and morphological responses to climatic variation cause a species to change. (curse you human variation!) |
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Phyletic gradualism
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The theory that new species are the result of gradual change involving the whole population.
Species formation called "anagenesis" |
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Punctuated equilibrium
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Duh.
Species formation called "cladogenesis" and "stasis" is used to describe periods of morphological stability. |
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Two theories of speciation
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Phyletic gradualism and punctuated equilibrium.
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Adaptive radiations
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Particularly inteisive periods of species generation and diversification. Associated with an opportunity to exploit a new environment, or when extinction in other groups give adaptive opportunities in existing environment.
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Clade
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Refers to all of the organisms descended from a recent common ancestor, no more and no less.
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How does cladistic analysis sort taxa?
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According to amount of morophology they share. The morphology used must be shared by two or more taxa, but also vary within the group under investigation, to break it up into subgroups, or clades.
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Sister taxa
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Two taxa that share specialized morphology.
The pair of sister taxa has its own sister taxon (Gorilla is sister taxon of Pan/Homo clade) |
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What assumptions does cladistic analysis work on?
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If members of two taxa share the same morphology,t hey must have inherited it from the same recent common ancestor.
But be careful of homoplasy! |
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Grade
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A category based on what an animal does rather than what its phylogenetic relationships are
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How to reconstruct ancient diets
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Microwear on teeth
Stable isotope analysis: measures oxygen, nitrogen, and carbon isotopes in fossil bones or deeth, and matches the pattern found in fossil with patterns seen in living animal with known diets |
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What biases and gaps can be seen in fossil record?
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-Majority of fossils are in later part of fossil record
-Much of the postcranial skeleton (vertebra, hands and feet esp) are poorly represented -Which parts of carcas predators like -Larger bodied taxa more likely to be fossilized -Some environments better for fossilization than others (soil conditions, etc) |
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FAD and LAD
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first appearance datum and last appearance datum
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What was the common ancestor of chimps and humans like?
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The common ancestor was probably more chimpish than humanish: Gorillas are living animals most closely related to chimp/human common ancestor (genetic and morphological evidence). Gorillas share more morphology with chimps.
Most like: evidence of being adapted for life in trees. Fingers curved, limbs both quadrupedal and habitual biped, snout-like face, elongated jaws, modest-sized postcanines, large canines, large upper first incisors |
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What early hominins probably look like (versus early panins)
Otherwise known as: the origin of hominin |
Predictions: smaller canines, larger postcanines, thicker mandibles. Anterior shift of foramen magnum, wider hips, straighter knees, and more stable foot)
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Lumper philosophy of early stages of hominin evolution
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Only 3 possibilities for 8-5my old higher primate fossils closer to pan/hom than gorillas or orangs:
1. Belong to chimp/human common ancestor 2. Primitive panin ancestral to living chimps 3. Primitive hom ancestral to modern homs |
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Splitter philosophy of early stages of hominin evolution
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Considers it likely that first homs and pans were just two of a number of closely related lineages
Only 3 possibilities for 8-5my old higher primate fossils closer to pan/hom than gorillas or orangs: 1. Belong to chimp/human common ancestor 2. Primitive panin ancestral to living chimps 3. Primitive hom ancestral to modern homs 4. Could belong to an extinct clade that is siter taxon of pan/homo clade 5. Could belong to one or more extinct panin and hominin subclades Expect to find evidence of homoplasies, which complicates because it's hard to tell homs from taxa that independently evolved to share one or more features |
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Sahelanthropus tchadensis: habitat, discovery
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Michel Brunet in 2001 in Chad
6 - 7mya Back then, habitat: lakes, grassy woodland, rivers and forests |
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Sahelanthropus tchardensis: morph features
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-brain chimp-sized
-hom-like browridges -thicker mandible -canine worn at tip |
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Orrorin tugenensis: habitat, discovery
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k/ar dated to 6mya. a tooth in 1974, and twelve other specimens since 2000. Brigitte Senut and Martin Pickford
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Orrorion tugenensis: morph features
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-thick enamel on postcanines
-Cortical bone on neck of femora is preferentially thickened on top and bottom of the neck (in chimps, it's equal thick all around) |
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Orrorion tugenensis: arguments against
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-morphology of the femur is not much different from that of pirates that move around in trees
-hasn't been demonstrated that thick enamel is confined to hom clade -much of tooth morphology is "ape-like" |
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Ardipithecus ramidus: morph features
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-foramen magnum more anterior than chimps
-lack info about brainsize, and evidence for posture and locomotion is scant. -similar size to modern chimpo -would look fairly ape-like **supplement with information from notes** |
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Australopithecus afarensis: habitat, context of discovery
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1978, from Laetoli in Tanzania and Hadar in Ethiopia.
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Australopithecus afarensis: features
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Fossil record includes a skull, several crania, many mandibles, and some postcranial limb bones
400 - 500cc brain volume Smaller incisors than chimps, but postcanines are larger than chimps (suggests that diet included more hard-to-chew items) Size and shape of pelvis and lower limb suggest habitual bipedalism over short distances Laetoli footprints |
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Australopithecus anamensis: habitat, context of discovery
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3.9 - 4.6mya in Kanapoi
Maybe one 3.5mya from Bahr el ghazal in Chad |
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Australopithecus anamensis: features
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Canines are more chimp-like than afarensis, yet postcanines are different than chimps
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Australopithecus garhi: context of discovery
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2.5mya, in the middle awash in Ethiopia
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Australopithecus garhi: features
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Limb bones suggest bipedalism, but postcanines are larger than afarensis, anamensis,
Found with animal bones that have been scraped by sharp-edged tools??? |
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Taung child
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Australopithecus africanus, found 1924, southern Africa by Raymond Dart. Supported by Robert Broom
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Sterkfontein
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Has some africanus remains, but also found Paranthropus robustus. Cave site.
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How do they date things at south African cave sites?
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Comparing remains of mammals found in caves with fossils at better dated sites in east Africa
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Differences between Au. africanus and Au. afarensis
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Africanus postcanines bigger, skull not as ape-like. Average brane volume a bit bigger. Capable of climbing trees as well as bipedalism
Africanus habitat: grassy woodland |
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OH 5
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Paranthropus boisei
Larger postcaninens than robustus, but small incisors and canines |
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Paranthropus boisei: features
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Only hominin with massive, wide, flat face with very large postcanines and small incisors and canines. Brain is around 450ccs, similar to africanus.
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Paranthropus aethiopicus: features
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A more projecting face, larger incisors, more ape-like cranial base. Older than 2.3mya
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Homo habilis: context of discovery
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In Olduvai. OH62
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Homo habilis: features
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Brain 600 - 700cc (although size of enlarged sample is from 500 - 800cc)
Found with stone tools (Leakeys thought habilis made the tools instead of boisei) |
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Functional criteria for Homo
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*supplement with stuff from notes
Dexterity and tool use, upright posture, and fully bipedal locomotion. Priorly, they thought should have brain size of at least 750ccs Looking for an adaptive niche |
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Homo habilis: case against
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Size of jaw and teeth to estimates of body size, habilis is similar to australopiths than to later HOmo
We now know that language is more distributed across brain than just Broca's area Postcrania differs little from Australopiths and Paranthropus Hand bones at Olduvai show just as much ability to make and use stone tools as afarensis and robustus |
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Homo rudolfensis: features
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What people thought were Homo habilis, but vary too much
Compared to habilis: has a larger brain 700 - 800cc, bigger, wider, flatter face, and large postcanines (suggesting different diet) No deets on the postcrania |
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Homo ergaster: context of discovery
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A little less than 2mya in Koobi Fora and West Turkana in northern Kenya
Jaws of H. ergaster smaller than those of archaic and transitional homs (either it ate different foods Lower limbs similar to modern humans...long legs Little advance over H. rudolfensis in brain size |
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Dmanisi in the Caucasus
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Earliest good fossil evidence for homs beyond Africa.
Radioisotope age of lava beneath sediments and fossil animals around homs suggest an age around 1.7 - 1.8 mya H. ergaster-like creatures with Oldowan stone toold |
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How people realized that we evolved on Africa
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1. Redating of Levant fossils: modern-looking ones were older than what they thought were Neandertals. Couldn't use dating evidence to make case that Neandertals evolved to modern humans
2. Discovery of modern human-looking fossils in southern Africa and Ethiopia (Omo 1 and Herto), dated recently to around 200kya 3. mtDNA. Has a high mutation rate and only comes from mum. More variation within Africa than outside of it |
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Three factors to examine to speciate
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1. Behavior
2. Phenotype 3. Genotype |
