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Terms in this set (141)

[--- A comparative method of dating the older of two or more fossils
or sites, rather than providing a specific date
-estimation of date based on location, type, similarity, geology, and association; includes pollen analysis, ice core sampling, stratigraphy, seriation, linguistic dating, and climate chronology]
1) Biostratigraphy = sites can be assigned an approximate age based on the similarity of animal remains to those from other dated
sites; concerned with recognition of fossils and the relative position of their occurrences in space and time in terrestrial and marine environments
2) Fluorine = based on the
accumulation of fluorine in a bone; its relative bc process of fluorine accumulation varies from site to site; fluorine is element found in ground water; skeletal remains can change mineral composition when ground water comes in contact with them; hydroxyl ions are replaced by soluble fluorides (fluorapatite) which accumulate over time; this dating can determine whether skeletal remains found in association with other bones were buried at the same time
3) Nitrogen = nitrogen occurs in bone in form of collagen which is lost slowly during fossilization; so the older the bone is, the less nitrogen it will have
4) Stratigraphy = makes use of the geologic process of superposition (the cumulative buildup over time of the earth's surface); When an organism dies or a tool is discarded on the ground, it will ultimately be buried by dirt, sand, mud, and other materials; dating method based on
the fact that older remains
are found deeper in the
earth because of cumulative
buildup of the earth's sur-
face over time
*5) Paleomagnetic reversals = method of dating sites based
on the fact that the earth's
magnetic field has shifted
back and forth from the
north to the south in the
past at irregular intervals; by comparing sample with the calibrated record (found with absolute dating techniques) you can get range of possible dates
[-determines exact date (subject to statistical fluctuation)]
1) Radiometric (Chronometric) Dating = relies on physical and chemical processes in
the universe that remain constant; radioactive elements discharge energy at a constant rate (deca rate); ex: Radium slowly turns into lead; can determine age of fossil by measuring amount of radioactive element
~Radio Carbon C-14 = obtains age estimates on organic materials (as old as 500-50,000 yrs); doesn't usually use bones; look at the rate of radioactive emissions for a sample and compare it to the rate of emissions expected in a living organism (one half life = 7.5 particles/second); developed by Willard Libby; radiocarbon determinations can be obtained on wood, charcoal, marine and fresh water shell, bone, antler, peat; __Radioactive carbon is produced when Nitrogen 14 is bombarded by cosmic rays in atmosphere which is then absorbed by plants and eaten by animals/humans; when organism dies, this Carbon 14 (different from normal C12) begins to decay back into N14__scientists measure how much C14 is disintegrated and how much remains to determine age; VERY ACCURATE; Problem= level of C14 in the atmosphere has not been constant in the past
~Potassium-Argon = measurement of the accumulation of Argon in a mineral (proportion of K40 to Ar40); only use for sample older than 100,000 yrs old; Potassium 40 decomposes and leaves Argon 40; takes 1.3 billion years for half the potassium 40 in a given sample to decay into argon; actual date is comprised of the time it has been formed from molten/heated minerals; the date that K-Ar method gives you on a rock can be reset bc the rock went through other changes so there's always standard error:+ or - 50,000
~Uranium 238 = measures radioactive decay of uranium-238 to uranium-234; used to date sediments in marine or lake environments; used for samples from 100,000 years to 1,200,000 years old
~Argon-Argon = A vari-
ation of potassium-argon
dating that can be applied
to very small samples of
volcanic rock (Ar 39-Ar40); radioisotopic dating method that measures the ratio of 2 argon isotopes:argon-39 and argon-40; measurements of both isotopes are simultaneously made at the same location in the crystal lattice where the argon is trapped; sample age is calculated by measuring both the argon-40 and argon-39 and knowing the (constant) ratio of potassium-40 to potassium-39 (K-39 is irradiated so it will transmute into Ar-39); more accurate because the final estimates can be calculated from a single extraction of argon gas even from a single crystal
2) Dendrochronology = dating of climatic changes through study of tree ring growth; can determine age within last 10,000 yrs; discovered by A.E. Douglass; wide rings produced in wet years and narrow rings in dry seasons; lots of growth in spring, smaller in fall, and none in winter; dry climates = one growth ring per year; By looking at a species with a known sequence of growth they can look for matching patterns in the unknown and perhaps see the past more clearly
3) Thermoluminescence = used for rocks, minerals, pottery between 300,000-10,000 yrs old; uses the fact that certain heated objects accumulate trapped electrons over time, which allows the date when the object was initially heated to
be determined; measurement of intensity of luminescence can date the object; Natural radioactivity causes latent thermoluminescence to build up so the older an object is the more light is produced; it actually determines the last time a crystal was heated and electrons were released
4) Electron Spin Resonance = chronometric dating that estimates dates from observation of radioactive atoms trapped in calcite crystals present in bones and shells; works best with dates under 300,000 yrs
5) Fission-track dating = based on the number of tracks made
across volcanic rock as uranium decays into lead; when uranium decays into lead in volcanic glass (obsidian) and other igneous rocks, it leaves small "tracks" across the surface of the glass. We can
count the number of tracks and determine the age of the obsidian from the fact that these tracks occur at a constant rate
1) Arboreal Model = 1st and oldest;
~because these creatures lived in a three-dimensional world they evolved full stereoscopic vision to be better able to move through the environment. The orbits of these early primates under went orbital convergence to achieve stereoscopic vision. Corresponding with this increase in reliance in vision occurred the reduction of olfaction and the shortening of the snout. Also grasping hands and feet with nails instead of claws was thought to be adaptations to living in an arboreal world
~Problem = there are orders besides primates that have arboreal species and none of them shows any of the adaptations found in primates

2) Visual Predation = 2nd
~orbital convergence, grasping hands and feet, and reduced claws were an adaptation for the nocturnal foraging for fruit and insects on terminal branches in the shrub layer of the forest. Orbital convergence would assist in gauging the prey's distance without having to move the head much
~BEST THEORY

3) Fruit = last;
~adaptive radiation primates occurred with the radiation of angiosperms (flowering plants) that offered new opportunities and an unexplored niche. The early primates were omnivores that were able to feed on objects such as fruits, flowers, gums, nectars, and insects that fed upon these plant parts. The stereoscopic vision evolved to discriminate between food items at low levels of light and handling them would have necessitated better hand-eye coordination
~Problem = angiosperms first appear in the fossil record millions of years before the first primates
-Late Oligocene, Early Miocene hominoid (23-28 Ma); name means before chimpanzee

-earliest family of fossil apes; probably a common ancestor of later hominoids (apes, humans)

-lived in east African forests btwn 23-18 Ma; ate primarily fruits, adapted to forest living; was successful for millions of years

-TRANSITIONAL FORM FROM EARLY GENERALIZED ANTHROPOID TO HOMINOID; EARLY FORM OF HOMINOID

-Monophyletic group = they evolved in one adaptive radiation from ancestral Old world primates, probably the propliopithecids

-this genus shows considerable variation, especially in size (from cat size to gorilla size) and locomotion and dietary adaptations, so assigning organisms in this genus to a certain species is difficult

-Skeletal structure =
-limb structure suggests they were unspecialized arboreal quadrapeds who ate fruit; a mixture of monkey and ape features; have primitive catarrhine cranial traits
~like apes and humans = no tail; shoulders and elbows; skull is more like ape and is large relative to body size; premolars;
~like monkey = limbs are all about same size; arms and hands; postcranial remains

-Why are they hominoids? = the shape of the lower premolars is more like ape bc it has single dominant cusp instead of 2 equal-sized cusps

-once thought to be direct ancestor of chimpanzees and gorillas

-Climate = eventually got cooler and drier so Proconsul habitat shrank and competition for dwindling resources increased; other hominoids developed that were more successful in new climate

-Dental traits = upper molars of squarish shape w/ belt of raised enamel on the tongue side (lingual cingulum); lower molars w/ a broad posterior basin (trigonid basin) w/ 5 cusps (Y-5); shows they had range of dietary patterns (some ate fruit w/rounded molar cusps and other ate leaves w/ shearing crests and cusps like earlier primates)
-this genus is bipedal = bc position of foramen magnum

~A. kadabba =
-more primitive than ramidus;
-When = 5.8-5.2 Ma (Late Miocene)
-Where = Africa
-kadabba = basal family ancestor
-Fossil characteristics = very apelike teeth; teeth and only a couple other skeletal remains have been found

~ A. ramidus =
-"ground ape"; early primitive hominin;
-ramidus = root
-Location = Ethiopia
-When = 5.8-4.4 Ma (Late Miocene, early Pliocene)
-Fossil characteristics = more human like teeth; most of what is known about Ardipithecus is from a partial skeleton of this species discovered in 1990's nicknamed "Ardi"
-Ardi = an adult female, with an estimated height of about 4 feet and an estimated weight of more than 110 pounds
-Characteristics ==
1) similar to apes = small ape size brain, cranial capacity about same size as female chimpanzee; middle of face protrudes like ape, but the lower face doesn't; smaller molar teeth than later hominins; thin enamel like african apes; omnivorous with lots of fruit
2) similar to humans = bipedal, lower face doesn't protrude, small canine teeth, omnivorous
3) similar to both = the pelvis shows ape and human traits; means that it was biped but also a frequent climber
4) unlike apes and humans = legs and arms same length; no adaptation in hand and wrist bones for climbing (suggests it supported itself on all fours while in the trees); big toe is divergent which suggests it climbed on top of branches

-IMPORTANT = likely walked on the tops of branches resting on its palms (like a monkey) but, when it descended to the ground, it walked on two legs ; not yet an obligate biped; EXISTED CLOSE TO BEGINNING OF BIPEDALISM BC IT HAS BOTH ARBOREAL AND TERRESTRIAL ADAPTATIONS
-Primitive hominins that lived in Africa (in Pliocene and Pleistocene 4.2-1.8 Ma)
-retained ape-like features in teeth and ape-like small brains; bipedal but probably climbed trees and walked on ground; ate primarily fruit in woodlands and savanna
-ancestor of both genus Homo and Paranthropus
-genus name translates to "southern ape" but is also found in east africa

~A. anamensis = hominin species that lived in East Africa 4.2-3.9 Ma (Pliocene); It was a biped but had many primitive apelike features of the skull and
teeth
-anam = lake
-Bipedalism bc = lower portion of tibia is perpendicular to ground like a human
-Apelike bc = canines tend to be fairly large, and the back teeth
are in parallel rows, a feature typical of apes and unlike the more parabolic jaw shape of humans
-TRANSITION BTWN ARDIPITHECUS AND AUSTRALOPITHECUS

~A. afarensis = east Africa 3.7-3 Ma (Pliocene) in Ethipoia
-Bipedalism bc = knee joint, footprints and Lucy!
-small, face juts out, back and bottom have primitive features; skull like a small ape
-teeth = less primitive than anamensis, but more primitive than later Australopithecus species
-Lucy = pelvic anatomy shows she's female; clearly shows bipedalism; erupted 3rd molar shows she was adult; very small probably 60 pounds and 3ft 5in; pelvis and postcranial bones show she was bipedal
--Differences between Lucy and humans = her arms were longer, curved finger and toe bones; still apelike characteristics even thought she wasn't as primitive as Ardipithecus
-the foot arches similar to those of humans suggests this species is obligate biped
-TRANSITIONAL FORM BTWN APES AND HUMANS
-ancestor of Paranthropus and HOMO

~~~Later Australopithecus~~~~~~
~~~Possible ancestors of Homo~~

~A. africanus =
- 3.3-2.5 Ma ( Pliocene and Pleistocene); south africa
-possible ancestor of Homo
-had much larger abck teeth than humans
-discovered by Raymond Dart; consisted of the face, teeth, and cranial fragments
of a young child; scientists didn't accept it @ time bc they thought large brain evolved 1st ; Based on
cranial evidence relating to the angle at which the spinal cord
entered the skull, he claimed that it was an upright walker; brain and protruding face were apelike but teeth were like humans (suggested bipedalism evolved first)

~A. garhi =
-Some suggest this is ancestor of Homo
-Ethiopia 2.5 Ma (Pleistocene)
-associated with possible use of stone tools
- Butchered animal bones showing these distinct stone cut
marks have been found near the discovery
-garhi = surprise
-very similar to afarensis but has very large front and back teeth (not specialized though) and is also very similar to Homo
- PROPOSED AS LINK BETWEEN A. AFARENSIS AND HOMO

~A. sediba =
-south africa 2 Ma (Pleistocene)
-characteristics link early hominins to Homo
-another possible direct ancestor of Homo
-sediba = fountain
-Similar to africanus = small brain, cusp structure of some teeth, some cranial features, long upper limbs
-Similar to Homo = dental anatomy, aspects of brain structure, pelvic shape, hands and feet
-POSSIBLE EVOLUTIONARY LINK BETWEEN AFRICANUS AND HOMO ( assuming africanus evolved into sediba who then evolved into first members of Homo and africanus wouldn't be our DIRECT ancestor)
-Transitional nature of this species=
1) Combination of small brain w/ shifts toward Homo frontal lobe anatomy suggests that a certain amount of brain reorganization took place before the expansion of the brain in the genus Homo
2) transitional pelvis suggests that the pelvis had begun to evolve before the evolution of larger brains, a change often felt to
have affected the evolution of the pelvis because of the physical demands of giving birth to larger-brained babies
-Genus Homo evolved from a species of Australopithecus btwn 2.5-2 Ma (beginning of Pleistocene)

~H. habilis = on other slide
~H. rudolfensis =
- A species of early Homo from Africa that lived 1.9 million years
ago, with a brain size somewhat larger than H. habilis (752 cc) but with larger back teeth and a broader face.

-more primitive than habilis

-some fossils classified as habilis are instead classified as this

-name comes from Lake Rudolf (Turkana) in Kenya

-endocast of their brain shows fissures and other typical Homo features (and unlike apes or Australopithecus)

-some dental and facial measures, however, appear to be more primitive than habilis like the larger back teeth and the broader midfacial region

~H. erectus = appeared in Africa by 2 million years ago, having
an essentially modern skeleton, full bipedal adaptations, and a brain much larger than earlier hominins (roughly 70 percent the size of a modern human, on average). Homo erectus was the first hominin to expand out of Africa, moving into parts of Asia and Europee*. Homo erectus hunted, used fire, and invented a new form of general-purpose stone tool known as the hand axe

-characterized by increase in brain size relative to earlier hominins and widespread manufacture and use of stone tools;

-erectus has bigger brain than habilis that is more similar to modern humans

-"upright walking human"

~H. heidelbergensis = began to appear around 800,000 yrs ago; occupied parts of Africa, Europe, and Asia, and had a large brain, almost the same size as living humans, but still with a large face
and low skull. Hunting skills had increased by this time, and new methods of making stone tools had developed by 300,000 years ago
~H. sapiens = anatomically modern humans; appeared in Africa by 200,000 years ago, spreading out across the Old World
over the past 100,000 years. There is still debate over whether these expanding humans interbred with preexisting humans such as the Neandertals
~Dentition = long narrow incisors (while apes are short and squat), no diastema, no projecting canines, jaw is parabola shape

~Locomotion = bipedal (foramen magnum right under skull while its more posterior on apes); apes are quadrapeds and associated with brachiation

~Reproduction = human females - 5 to 6 times more offspring than ape females who can only have 4 to 5 kids; kids of humans and apes are dependent on moms for a long time; human can bear the rate of 1 every 12-18 months. Pongid mothers cannot, they bear young at the rate of every 48-60 months;

~Brain Size = brains of hominins are larger than apes. Our species has specialized in brain size, but increased brain size did not always distinguish the hominins

~Language = Hominins are able to communicate by means of articulate speech; apes are not, but can be taught to recognize the meaning of signs; Though apes and humans share in common some areas of the brain necessary for speech, there is some evidence that apes lack the necessary vocal anatomy to be capable of producing all the sounds needed for speech like the length of larynx (too high ans too short)

~Culture = phenomenal success of our species has been due in large part to culture. The record of cultural evolution is found in the abundant and continuous archaeological record. Stone tools appeared about 2.5 million years ago

~Female Sexuality = Human females are continuously capable of sexual arousal. Therefore sexuality is more continuous in hominins than apes. Ape females are sexually receptive only during intermittent periods of heat which are characteristic of the estrus cycle. Continuous capacity for sexual arousal appears to be the most basic of several significant changes which human females have undergone
; -first arose 6-7 Ma around the time of the divergence of hominins and African apes as estimated from genetic data

-this is the first unique human trait that evolved (NOT BRAIN SIZE); evolved millions of years before the beginning of significant brain expansion

-Our ancestors therefore went through a time when they were likely very apelike in behavior, but spent much time walking on two legs; modern humans are obligate bipeds

----Hypotheses about the locomotion of the ancestor of the first hominins:::
1) the common ancestor was a generalized climber; two evolutionary shifts: bipedalism in the hominin line, and knuckle walking in the African ape lines. However, this hypothesis requires that knuckle walking evolved twice, once in the line leading to the gorilla and again in the chimpanzee-bonobo line; requires parallel evolution of knuckle walking to have occured
2) common ancestor was a knuckle-walker; Here, all of the African apes retained the knuckle-walking adaptation of the
common ancestor, and the only evolutionary change occurred in the hominin line, a transition from knuckle walking to bipedalism;
*it does not seem likely that
hominins and African apes evolved from a knuckle-walking common ances-
tor because the hand and wrist bones of Ar. ramidus do not show any evidence
of a knuckle-walking ancestry, but instead show a creature that supported
itself on its palms *

-Environmental context of origin of bipedalism =
-In late Miocene, climate got cooler/drier; led to small patches of forest surrounded by grassland/savanna
-new evidence for the environment of the earliest possible hominins. Prior to 4.4 million years ago, hominins did not occupy the open grasslands but lived in relatively wet forests and woodlands
-Anthropoids went through adaptive radiation

-Major changes during this period = 1) appearance of first elephants with trunks; early horses; appearance of many grasses; mammals such as horses, deer, camel, elephants, cats, dogs, and primates began to dominate, except in Australia
2) continuation of land mammal faunal migration between Asia and North America was responsible for the dispersion of several lineages onto new continents
3) The "bulk feeding" in the open grasslands and savannas that occurred in this period resulted in the increase of general herbivore size (caused ungulates [hoofed mammals] to get larger)
4) Early forms of amphicyonids, canids, camels, tayassuids, protoceratids, and anthracotheres appeared, as did caprimulgiformes (birds that possess gaping mouths for catching insects). Diurnal raptors, such as falcons, eagles, and hawks, along with seven to ten families of rodents also first appeared

-Fossils = there's evidence of anthropoid fossils at start of this epoch in the New and Old World; most fossil evidence in South America, Africa, eastern Asia

-Climate = cooler, expansion of grass lands, reduction of forests; resulted in southward movement of primate populations; cooling trend caused marine biotic provinces to become more fragmented bc some that could handle the cool temps went further from equator AND caused reduced diversity in marine plankton which are the foundation of marine food chain

-Primate characteristcs = showed continued radiation of anthropoid forms in Old and New world; continues reduction of snout and nasal area indicating reliance on vision, not smell; fully closed eye socket with smaller eye orbits which is characteristic of modern anthropoids and shows they were diurnal; small, arboreal, quadrupeds; ate mostly fruit w/ some insects and leaves;
-Bipedalism probably originated bc all of these things played a role

1) Tool use model = Darwin; as tool use increased and became more important, natural selection led to larger brains and enhanced
learning abilities. As larger brains evolved along with longer periods of infant and child dependency, tools became even more important for survival. Thus, tool use affected brain size, which in turn affected tool use. Tool use would benefit from walking upright, such that the model predicted a simultaneous evolution of bipedalism, larger brains, and tool use; REJECTED bc fossil evidence shows bipedalism evolved way before anything else; BUT the basic idea that bipedalism offers an evolutionary advantage
by freeing the hands to carry things may still have some merit; possible that environmental changes prompted an increase in simple tool use that led to a selective advantage for bipedalism

2) Predator avoidance = walking upright would have allowed for better detection of predators on the savanna (where there are fewer
places to hide) because an upright hominin could see farther

3) Reproductive success = hominin could also have carried food and infants, which, under the right conditions, could promote increased survival and reproduction; Lovejoy has suggested that bipedalism
evolved as a strategy to increase the survival of infants and other dependent offspring by having some group members forage for food and then carry it back to the group. Consequently, more infants could be cared for, allowing
an increase in reproduction and potential population growth

4) Food acquisition = Bipedalism may have first evolved as
a feeding posture and secondarily as a way of moving around on the ground in the forests and woodlands; this model fits well with the fossil evidence for bipedalism of the earliest hominins, which suggests a life spent partially on the ground and partially in the trees

5) Temperature regulation = we
have evidence that being bipedal reduces heat stress on the savanna during
the hottest times of the day

6) Energy efficiency = Bipedalism is more energy-efficient in traveling long distances in search of food. Increased energy efficiency means using less energy to move
about looking for and gathering food; Energy efficiency is
often considered in terms of an adaptation to open savanna environments and long distances to travel; woodland/forest environments were shrinking and they may have needed to travel more between shrinking clusters to find enough food. As the forests and woodlands continued to shrink, the energy-efficient advantage of bipedalism may have continued to increase