2202 Exam 3
3 theories for the dispersal of AMHS
-Multiregional Continuity Model -Out of Africa Model -Assimilation Model
Neanderthals
Anatomical features include low forhead, long, low braincase, occipital bun, supraorbital torus, projecting midface, large cranial capacity (1,200-1,750 cc (larger than AMHS)), lack of chin, large front teeth, projecting midface, and large arching browridges. Cold adapted features include: •Wide nasal aperture (Large nose warms and moistens frigid air) •Large infraorbital foramina to carry blood vessels (Greater blood flow to prevent facial freezing)
Emergence and dispersal of anatomically modern Homo sapiens
Anatomically modern Homo sapiens had evolved in Africa by 200,000 years ago. They reached Western Asia by 90,000 years ago, and Europe by 32,000 years ago. Keep in mind that there were already other hominins living in Asia and Europe at the same time - Neanderthals in Europe and H. heidelbergensis or Denisovans in Asia. AMHS would have met, interacted with, and interbred with these other hominin species, but by 25,000 years ago the only hominins left in existence were AMHS.
Ante/peri/postmortem injuries
Antemortem - before death Perimortem - near time of death Postmortem - after death
Ardipithecus ramidus ("Ardi")
Ardipithecus ramidus, or Ardi for short. Ardi is the most complete early hominin ever found, and lived between 5 and 8.4 million years ago. This is the finding that changed what we know about the environment of bipedal evolution and debunked the patchy forest hypothesis. Ardi is clearly a partially bipedal hominin, but lived during a time period when the environment would have been dominated by woodland forests.. Determined to be a female, she had a large supraorbital torus, or brow ridge, a small brain, reduced canines, and little dental specialization. But what's really interesting is the morphological traits associated with locomotion. They indicate Ardi was likely partially bipedal, and partially arboreally quadrupedal. She had a more centralized foramen magnum and a short, broad, bowl-shaped pelvis, all traits associated with bipedal locomotion. But she retained some traits associated with arboreal quadrupedalism as well - an opposable hallux, long, curved phalanges good for grasping and climbing branches, and longer arms than legs. Thus, Ardi represents a transitional species on the way to complete bipedalism.
Culture of Neanderthals
Diet: primarily meat and cooked vegetables Clothing: •First evidence: 540 KYA (H. heidelbergensis) •Needles/awls Body decoration: •Flight feathers Art: •Necklaces (bone & teeth) - 35 KYA •Cave paintings - 40 KYA Tools •Mousterian Complex •Made from flint/chert •LeVallois technique Technology •Wood-working & hide-working •Spearheads •Engraving tools Music •Flute - 43 KYA Burial •Flexed position •Few grave goods -Flowers? •Care for elderly? Living sites •Some evidence of structures •Numerous cave sites -Organized living area •Hearth in middle •Stone chips, animal bones (trash) in back of cave
Bering Land Bridge
During the glacial maximum when humans would have been migrating this way, the sea level would have been lower as much more of it would have been tied up in glacial ice. This exposed land bridges, including the Bering land bridge in Beringia. This land bridge today is underwater, but at that time, it would have created a connection between Siberia and Alaska for humans to access North America. The second wave of humans also came over the Bering Land Bridge from Asia between 15,000 and 17,000 years ago, and traversed the continents reaching the Atlantic coast by 10-13 thousand years ago and South America by 11,000 years ago. Additionally, we can track both Y-chromosome and mtDNA genetic data to recreate migration patterns of these people.
Gracile Australopithecines
Gracile: In gracile australopithecines, the anterior teeth are emphasized and the premolars and molars, or the chewing teeth, are much smaller. There are no significant differences in body size between gracile and robust. -A. anamensis -A. afarensis -A. africanus -A. garhi
Homo erectus
Homo erectus is the longest lived hominin in our history. By this I don't mean that they lived the longest lives, but that they walked the earth for the longest time of any species we've covered so far or will cover in this unit. They existed from 1.8 million years ago to 300,000 years ago - that's 1.5 million years! This extremely successful species was the first to migrate out of Africa, spanning the continents of Asia and Europe. The map here shows all the sites across this area of the world that we find Homo erectus fossil remains. African Homo erectus developed a new tool complex called Acheulean tools. As you can see, these tools are much more intricate and finely worked than the older Oldowan tools. They were bifaced, meaning they were shaped on both sides to create a finer, sharper edge. They were also made using a soft hammer technique. Unlike previously where tools were made by simply hitting two stones together, the soft hammer technique required using a softer material such as bone, antler, or wood to hammer off smaller pieces of stone. When removed, such small flakes reduced the coarse and jagged edge to many small serrations, giving a straighter and more uniform cutting edge whose angle was sharper. Homo erectus was the first hominin to intentionally use fire - we have evidence of ash pits in areas occupied by groups of Homo erectus. With fire comes cooking! Cooking increases the digestibility of more foods allowing them to get more nutrition out of their resources. It also softens the food which reduces the chewing forces necessary - thus we see a reduction in robusticity of the jaw and tooth size. This would have been necessary to fuel an increasingly large brain. Cooking removes toxins from food as well, reducing parasite load and illness.
Australopithecines
In Latin, Austral means southern, so the Australopithecines are named the "Southern Apes" in Latin. Their fossils have been found mainly in southern and eastern Africa in abundance. The map on this slide pictures the main site names where australopithecine fossils have been found. Try to pay attention to which were found in east vs. south Africa, as we can see different evolutionary patterns occurring in each area. Australopithecines walked the earth for a span of about 3 million years - from 4 million to 1 million years ago before they disappear from the fossil record. They were bipeds, but weren't completely efficient bipeds as we'll see from looking at their morphological features. They had pretty small brains and small bodies. Their brains range in size from 340-500 cubic centimeters, or cc's. For reference, the average modern human brain is about 1200-1300 cc. They weighed between 64 and 100 pounds, and many were sexually dimorphic.
Holocene evolution
Independent origins of agriculture: Agriculture wasn't developed by one group of people originally and then spread - archaeologists have determined that agricultural practices were independently developed all over the world. Some of the major hubs of these developments exist in China, Mexico, New Guinea, Eastern North America, South America, and Sub-Saharan Africa. On the image above, you can see the different types of crops that were originally cultivated in each area. Anatomical changes to skull: Although humans are considered "anatomically modern" starting way before agriculture hit the scene as you'll remember from our last lecture, the consequences of the agricultural transition were so marked that they changed the morphology of many of our skeletal features. Remember that according to Wolff's law, bone is a dynamic, living tissue that responds to outside mechanical forces. Agricultural foods like corn, wheat, and rice are much softer and easier to process than the foraged foods of hunter-gatherers. With a decreased mechanical load for chewing, our skulls became rounder and taller, our jaws became smaller and more gracile, and our chins receded. Health Changes: Increased infectious disease •Due to over-crowding and unsanitary conditions Cribra orbitalia and porotic hyperostosis •Caused by nutritional deficiencies in vitamin B12 and vitamin C •Also caused by infectious pathogens -Nutrient losses from diarrheal disease and intestinal parasites •Causes abnormal break down of red blood cells in marrow cavities Oral Health •Increased dental caries •Enamel hypoplasias •Overcrowding of teeth
Sahelanthropus tchadensis
It lived about 7 million years ago, very close to the time period of our last common ancestor with chimpanzees. This specimen is very interesting in many ways - it was found in north-central Africa, far away from most other hominin fossils in east and south Africa. We only have a skull, no post-cranial remains of this species, but luckily the skull can tell us many things. Sahelanthropus shows a unique combination of features that are not seen in fossil apes of the same period, nor later hominin species. They had small teeth with very thick enamel, a short face, and decreased prognathism. They also had a very large and protruding supraorbital torus, or brow ridge. However, the most important feature is the position of the foramen magnum. It is not completely underneath the skull like in humans, but is about halfway between the position of a chimp's and a human's. This means that bipedal locomotion was already under selective pressure. The foramen magnum was traveling anteriorly to support a new form of locomotion.
Speech capability of Neanderthals
Neanderthal hyoid bones are very much like our own. The hyoid is important for the physical ability to create speech, as it forms an anchor for the tongue and other muscles of the throat and is involved in the creation of the distinguishable sounds that allow us to speak to each other. But the physical ability to speak isn't the only piece of the puzzle, you also have to have the cognitive ability to create, use, and understand language, and that's where genetics come in. As Neanderthal remains are young enough to not have fossilized completely yet, geneticists have been able to sequence the entire Neanderthal genome from their bones. They found that the FOX P2 gene in humans that allows us to use language was identical in Neanderthals. Therefore, it's likely that they had both the ability to speak and use language.
Orrorin tugenensis
Orrorin lived about 6 million years ago. However with this species, we don't have any cranial remains, only post-cranial remains and some teeth. Luckily we have a relatively complete femur, which can tell us a lot about their locomotion. We see an elongated femoral neck, which indicates that Orrorin was at least partially bipedal. The curved phalanges indicate they were also partially arboreal. The teeth were small for their body size, and the canine teeth were ape-like but reduced in size. This species is a good representation of the transition from the trees to the land.
Homo habilis
Our first species of the Homo lineage is Homo habilis. Habilis was nicknamed the "handy man" when it was originally found because it was the first hominin species to ever be found in association with stone tools. If you remember back to our last lecture, you'll know that some australopithecine species actually earned this title, but it was still a hugely important find at the time. Habilis fossils are generally found at similar locations as australopithecines, mainly in east Africa but also some in South Africa. Keep in mind habilis would have been alive at the same time as some of the australopithecine species we already talked about. The sites shown on this map are those where habilis fossils were found most often. -Descended from Australopithecus garhi
U-shaped dental arcade
Parallel dental arcade of apes, more prognathic
Robust Australopithecines
Robust: the robust species skulls are emphasized where chewing muscles are attached. Look at the large sagittal crest on the individual on this slide as well as the large nuchal crest around the back of the skull. In the robust australopithecines, they have what is called megadontia or gigantic teeth. There are no significant differences in body size between gracile and robust. -A. robustus -A. boisei -A. aethiopicus
Determining Sex
Sex: In the skull alone, we use 5 different morphological features each scaled from 1 to 5, 1 being definitely female and 5 being definitely male. All of these features are then averaged, and an anthropologist makes an estimation of sex. The pelvis is generally an even better way to estimate sex, as the most exaggerated sex differences are observed here. We also use a number of different morphological features here - sex is never determined on the basis of just one feature. One feature we use is the subpubic angle, this is the anterior angle formed by the pubic bones where they meet. In females it is generally wider, and in males it is generally narrower. Females also have a larger and less obstructed pelvic outlet, with the sacrum tilted backwards to allow for the passage of a baby. Males tend to have smaller pelvic outlets. One more feature used in sex determination is the shape of the pubic bone where it's indicated with the red arrow. In females, this feature is thinner and more concave. In males, it tends to be thicker and either straight or convex.
Blunt force, sharp force, and ballistic trauma
Sharp force trauma is caused by some kind of blade, whether that be a knife, an axe, a sword, or anything else of that nature. Sharp force trauma leaves sharp edges, shears, and cut marks easily distinguishable from other types of trauma. Blunt force trauma is caused by a blunt object, like a rock, a bat, a hammer, or anything without a sharp edge. These injuries are noticeably different from sharp force. They tend to be concentric depression fractures that radiate out from a center strike area. The last type of injury is ballistic trauma, caused by a projectile like a bullet. These injuries are very complex, and anatomical knowledge of not just the skeleton but the soft tissues as well is necessary to determine exactly how much damage would have been caused by a bullet.
Ancestral trait
Some examples of ancestral traits: posterior foramen magnum, prognathism, thick enamel, thick supraorbital torus, curved phalanges, divergent hallux, longer arms than legs, sloping frontal bone, sagittal crest
Derived trait
Some examples of derived traits: anterior foramen magnum, vertical forehead/frontal bone, orthognathism, straight phalanges, adducted hallux, valgus knee, longer legs than arms
Bioarchaeology
Study of historical and ancient human skeletal remains Insights into nutrition, health, activity in past populations
What makes the Homo genus thrive?
The climate at this time was highly variable. A variable climate results in lots of different types of habitats. A species that is adaptable is going to be successful when the climate is fluctuating, and that's exactly what the members of the homo genus were. They were adaptively plastic - they were gaining increasing intelligence to manipulate their habitats and acquire resources, and their tools allowed them an increased ability to exploit food sources that would have not been available to them otherwise.
Assimilation Model
The final hypothesis is called the Assimilation Model. This hypothesis is similar to the Out of Africa Model, in that it proposes AMHS migrated out of Africa around 100,000 years ago. However, this model says that there was significant admixture with Neanderthals, Denisovans, and Asian H. heidelbergensis, not just out-competition and replacement of these species. The hypothesis most supported by current paleoanthropologists is the Assimilation Model, as there is both morphological and genetic evidence to back it up. We now know based on genetic studies that modern people with ancestry outside of sub-Saharan Africa share a percentage of their DNA with Neanderthals or Denisovans.
Out of Africa Model
The first hypothesis proposed is called the Out of Africa model. In this model, AMHS migrate out of Africa around 100,000 years ago. They then replace H. heidelbergensis in Asia and Neanderthals in Europe, outcompeting them. In this model, there is no admixture, or interbreeding, between species.
Diet of Australopithecines
The gracile species ate much softer foods compared to the robust species. The gracile australopiths were likely omnivorous, eating a broad range of foods including fruits, tubers, nuts, scavenged meat, and plants. The robust australopiths had ideal dentition and cranial morphology for eating hard, tough foods like seeds and nuts, as well as grasses. In fact, recent studies have shown that the robust diet consisted of up to 80% grasses. Think about cow or horse teeth, they're HUGE because grass is a low quality food that requires eating a lot of it, and lots of grinding to break it down.
Early archaic Homo sapiens
The hominin species Homo heidelbergensis, also known as early archaic Homo sapiens. The reason we can call them different things is because there is a lot of debate amongst paleoanthropologists as to how exactly to classify them. Homo heidelbergensis represents somewhat of a wastebasket taxon - they consist of many similar hominin fossils that existed between Homo erectus and the appearance of truly anatomically modern humans. Generally speaking, H. heidelbergensis shows a mixture of earlier H. erectus traits and later anatomically modern human traits. They appeared in Africa, Asia, and Europe around 350,000 years ago. H. heidelbergensis shared traits with both its predecessor, H. erectus, and it's descendant, H. sapiens. It had a similarly long, low oval-shaped brain case with a receding forehead. It also had a large supraorbital torus and a large, heavy mandible with no chin. However H. heidelbergensis also shared many traits that wee see in later anatomically modern H. sapiens (us!). Most notably, they had a large cranial capacity around 1200 cc, which is well within the range of modern human brain size. They were less prognathic than H. erectus, and the cranium was rounder overall - with reduced post-orbital constriction, expanded sides of the cranium, and a rounder occipital bone.
Bipedalism
The morphological changes associated with bipedalism in evolution: i. Anterior position of the foramen magnum- more anterior ii. S-shaped spine- weight distribution iii. Short, wide pelvis- bowl-shaped to support our internal organs iv. Limb ratio (longer legs than arms)- Longer legs allows a longer, faster more energy efficient stride v. Femoral angle- Allows for energetic efficiency, balance and weight distribution while walking bipedally · Bicondylar angle-The angle measured when the distal end of the femur articulates with the proximal end of the tibia at an angle less than 90 degrees. · Valgus vs. varus knee- Valgus knee- bicondyler angle, found in bipeds like humans, varus knee- straight angle, found in quadrupeds vi. Adducted hallux- Humans are the only primates without opposable big toes. Reason is we need more stability in our feet to move and balance. vii. Dual-arched foot (transverse and longitudinal arch)- Humans have a double arch system in each foot. A transverse arch across the top of the metatarsals, and a longitudinal arch across the bottom of the foot. Absorb extra weight due to bipedalism. We also have enlarged calcaneus as well.
Multiregional Continuity Model
The next hypothesis is called the Multiregional Continuity Model. In this model, it's proposed that modern humans evolved independently within their respective regions, although earliest in Africa, and gene flow along the borders of populations insured that eventually over time, all became the same species. In other words, humans would have evolved from Neanderthals in Europe, Denisovans or H. heidelbergensis in Asia, and H. heidelbergensis in Africa, but due to interbreeding between populations all eventually ended up as the same species that we are today.
Forensic Anthropology
The scientific application of physical anthropology in a medico-legal context •Identify modern individuals / circumstances of their death
Lumpers vs. splitters
There are two camps of paleoanthropologists that become more apparent with Homo erectus - those who think it's best to split the three geographic variants into three separate species are splitters, and those who think they all belong to the Homo erectus species are lumpers. Lumpers argue that although the individuals found in Asia, Africa and Europe are different, they represent a normal range of geographic variation much like we see in modern humans. •Asian forms - H. erectus •African forms - H. ergaster •European forms - H. antecessor
Laetoli footprints
These are the fossilized footprints of at least two individuals, maybe more, dating to 3.6 million years ago. These footprints are so cool because they show us what their stride would have looked like with not only the bones of the foot, but also the soft tissues. What we see when we look at these footprints is something very like our own - we see that they have developed an adducted hallux like ours. This indicates they have made a continued commitment to bipedal locomotion. We also see a double arch has formed in the foot - another sign of clear bipedality. This is also our first clear evidence of sociality in hominin species. If you think about it, when we find individual fossil remains, there's no way to know exactly what individuals they would have interacted with, what kinds of groups they may have formed, and how they interacted with each other. However here we have clear evidence of a group traveling together. Some have argued that there are two adults, one pregnant, as the heel-prints are deeper in one set. Others have argues that this indicates a third, smaller individual walked in the prints of the other.
Australopithecus afarensis ("Lucy")
This species lived for a span of about 700,000 years - from 3-3.7 million years ago. We have a lot of examples of this species, including some relatively complete sets of remains, so we know a lot more about their morphology and locomotion. General features include a small brain and prognathic face, however they have a slightly more parabolic dental arcade than previous hominins. They were definitely bipedal, but they retained some arboreal adaptations, such as curved phalanges. famous Lucy. She is so famous because at the time she was discovered in Ethiopia in 1974, she was the oldest and most complete fossil hominin ever found. Her skeleton is 40% complete, so there is a lot we can learn from her. Lucy's remains are 3.2 million years old, so she was living towards the later end of this species' time on earth. Since we have a complete os coxa, we can tell that she is a female. Her stature would have been around three and a half feet tall. The really interesting thing we learn about Lucy however is her age: she's estimated to be 11-12 years old, but she is fully mature, meaning she has reached adulthood and all her bones have fused. What we learn from this is that the life cycle of australopithecines would have been faster than our own - they reached adulthood at an earlier age, had a shorter childhood, and probably reached old age and died much earlier than a modern human. At 3.3 million years old, these stone tools are the oldest ever found to date pushing back the original hypothesis of the first stone tools by a million years. These were pretty primitive stone tools created by knapping, or hitting stones together to strike off sharp flakes.
Homo floresiensis
This species was first discovered in 2004 and rocked the paleoanthropological world because of it's uniqueness and recent time on earth. Nicknamed "the Hobbit" due to its small size, H. floresiensis existed from 38-13,000 years ago in this part of the world only. Our evidence comes from 1 nearly complete skeleton and 13 partial skeletons. H. floresiensis was just over 3 feet tall, but was found with complex tools and showed a mixture of ancestral and derived traits. They shared some traits with H. erectus - cranial shape, robusticity, and a lack of chin, as well as some with H. sapiens - an orthognathic face and small teeth. The most probable cause of their diminutive size is called island dwarfism. This results when there is natural selection for a smaller body size due to the reduced amount of resources available on an island. Think about it this way - if you're smaller, you require less energy to survive. The remains of other pygmy animals dating to the same time period, including a pygmy elephant, were found in the same area. This indicates it was an evolutionary trend for many large species on that island.
Determining Age
To determine age, there are quite a few methods we can use. In those who have not yet reached adulthood, we can determine age pretty accurately based on dental development. Human teeth form and erupt with regular timing, so based on root formation, crown formation, and tooth eruption we can determine age. After adulthood this method isn't very useful. But there are population specific ways to determine age for adults based on tooth wear. For subadults we can also use bone fusion to determine age. Remember back to our osteology lecture - bones begin in 3 pieces, two ends and a middle. They fuse over time with age, although all bones fuse at different predictable times. Based on which bones have fused and which have not, we can determine subadult age with relative accuracy. In adults this method is not very useful, but we can use degeneration of the joints to help determine age.
Parabolic dental arcade-
Wider dental arcade of humans; bicuspid molars, smaller canines. Less prognathic
What sets Homo apart?
§Increased brain size §Larger brain proportional to body size §Brain sits higher in cranium §Round, high forehead §Less post-orbital constriction §More orthognathic §Clear tool use §More reliance on culture •Larger anterior teeth •Reduced posterior teeth •Complete loss of diastema •Parabolic dental arcade
