Wednesday, April 21, 2010

Three Major Hypothesis

I. Location of the Transition to Modern Humans

By the Middle Pleistocene, Homo heidelbergensis was spead out in Africa, Europe and Asia. Into modern humans evolved one or more of these populations. There is an argument weather modern humans originated in Africa, or the transition to modern humans was a worldwide phenomenon. Multiregional evolution model shows that human evolution took place within one lineage over the past 2 million years, from H. erectus, to H. heidelbergensis, to H. sapiens. Opponents say that human anatomy took place piecemeal across the Old World, with some changes, and modern humans resulting through the mixing of these changes through gene flow. The hypothesis of African origin states that human anatomy appeared first in Africa and then spread across the Old World. Fossil record supports the African origin hypothesis.

II. Replacement

According to African replacement model, modern humans emerged as new species in Africa about 200, 000 years ago and started to spread through the Old World, replacing preexisting human populations outside of Africa which became extinct and are not part of our ancestry.

III. Assimilation

Assimilation model proposes that the initial change took place in Africa, however changes were spread to other populations outside of Africa through gene flow. Genes got mixed, but not replaced.

Homo Neanderthalsis has been considered as a separate branch of human evolution. We do not have enough evidence to make any conclusions about Sahelanthropus tchadensis, so far, it is the one and the oldest specie with human like features. They are very important for understanding hominin evolution. We need to know where did we come from, so sometime we can understand where do we go. It is very important to know about our early ancestors and other human-like creatures which lived in the past for our own evolution and understanding of who we are and what makes us special, how can we survive and not extinct like they did.

A fossil of a 24,500-year-old early modern human child unearthed in Portugal shows distinctive Neanderthal characteristics, possibly the result of interbreeding. After that, all record vanish. Although DNA tests show that modern humans and neanderthals diverged from a common ancestor more than 500,000 years ago and that modern humans do not carry neanderthal genes and so did not interbreed when they encountered each other 50,000 years ago, the discovery of possible hybrids suggests that we still have not fully completed the Neanderthal story.

There is not much record about Saelanthropus tchadensis and his relatedness to modern humans. However, more we study and search, more we find out and with every single thing our world outlook can become 100% different.

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KNM-WT 15000



Nickname:


Turkana Boy


Site:


Nariokotome, West Turkana, Kenya


Date of discovery:


1984


Discovered by:


Kamoya Kimeu


Age:


About 1.6 million years ago


Species:


Homo erectus


The strapping youth


The ‘Turkana Boy’ skeleton has allowed scientists to find out a lot of information about body size, body shape, and growth rates of Homo erectus. Using bilateral symmetry to fill in missing bone (e.g., the missing left upper arm bone can be reconstructed as the mirror image of the right upper arm bone), his skeleton is over 90% complete.


The size and shape of the pelvis shows he was male, and his teeth tell he was eight or nine years old. He was 1.6 m (5 ft 3 in) tall and weighed 48 kg (106 lb) when he died; if he had reached adulthood, he might have grown to nearly 1.85 m (6 ft). Turkana Boy’s cranial capacity at death was 880 cubic centimeters, but scientists estimate it would have reached 909 cubic centimeters if he had grown into adulthood. There is evidence that he was growing up at a rate similar to modern humans, and he may have undergone an adolescent growth spurt characteristic of modern teenage boys. His cause of death at such a young age is an inflammation in mouth.


His long and slender body is evidence of an early human adaptation to the hot, dry climate of Africa. His long legs and narrow pelvis helped him walk farther, increasing his home range, and maybe even run long distances.


The Turkana Boy lived in a region of active volcanoes whose deposits can be dated. When ash or lava from a volcano has cooled, radioactive potassium 40 in the material begins to decay at a known rate to stable argon 40. By measuring the proportions of potassium 40 and argon 40 present today, scientists can determine how much time has elapsed since the rock formed, and, by inference, the age of fossils found in or between the rock layers. In recent decades, a refinement to the technique has involved measuring the ratio of artificially made argon39 to argon 40. Both conventional potassium-argon and argon-argon dating were used to determine that the Turkana Boy was sandwiched between volcanic ashes respectively dated to about 1.88 million and about 1.39 million years ago. By using measurements of how distant the skeleton was from each of these layers and assumptions about how fast the intervening layers would have formed, an estimated age of about 1.53million years was obtained.


The average day for Homo erectus would be in search of food. Having big body and twice as big brain as chimps he needed a lot of calories, and meat is a perfect source. However to get enough meet is very exhausting and hard. They were following a prey in the midday, because of the ability to sweat the could run for long distances and chase their prey(if they have been hunters). If they were scavengers, they would search carefully for leftovers after big hunting animals, or possibly even follow them carefully. At evenings they set along the fire and cooked their trophies, socializing and eating.

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Homo erectus 1


Some scientists devide the African (Homo ergaster) and Asian (Homo erectus sensu stricto) fossils of this taxon, while others bond them together as Homo erectus sensu lato. There is general agreement that it descended from an earlier species of Homo (e.g., Homo habilis) and represents one of the widest dispersals of early humans in our evolutionary history. It is likely that distinct populations of Homo erectus sensu lato led to the emergence of later homininspecies, such as Homo heidelbergensis, and to our own species, Homo sapiens.


At the beginning of its time range, around 1.9 Mya, H. erectus coexisted in East Africa with several other early human species including Homo rudolfensis, Homo habilis, and Paranthropus boisei. Sometimes they were even found at the same fossil sites. At the end of its time range, around 70,000 years ago, it coexisted with Homo floresiensis and possibly Homo sapiens in Indonesia.


· Homo erectus (1.8 million - 250,000 years ago)- Brain far bigger than Lucy’s (cranial capacity almost 900 cl)


· Long, slim body


· Two legs


· Straight back


· Short forearms


· Lower forehead


· Large supra orbital torus


· Post-orbital constriction suggests less development in the frontal and temporal lobes of the brain


· An occipital bun


· A large jaw with a wide ramus


· No chin


· The skull is lower


· Brow ridges


From the neck down the Homo erectus fossils appear like human skeletons and stood about 5 ft 6 in. A ridge along the top of the skull, the sagittal keel, is common in H. erectus , but it is not associated with muscles, it is simply a raised midline bony feature. Homo erectus species show sexual dimorphism which suggests that they might have had multiple partners, because difference in size between males and females are often related to monogamy.


Height:


Ranges from 4 ft 9 in - 6 ft 1 in (145 - 185 cm)


Weight:


Ranges from 88 - 150 lbs (40 - 68 kg)


Homo erectus had a recognizable tool culture, called the Acheulean tool tradition. They term pebble-tools of the

earlier Homo habilis Oldowan.


A handaxe that fits into the hand is the classic Acheulean tool, but they shaped these to serve as scrapers, side scrapers, backed knives, small choppers, picks, points and borers.


With the evolution of H. erectus , their tools became more standardized indicating improved communication and cognition between individuals. Tools differ within geographic regions where Homo erectus lived. They used fire as a source of energy. They used it for light, warmth, scaring night predators, cooking and socializing. Their diet consisted mostly of meat. Were they hunters or scavengers remains questionable. The producer of early art was the homo erectus, even before the Neanderthal man.

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Homo erectus



Where Lived:


Northern, Eastern, and Southern Africa;


Western Asia (Dmanisi, Republic of Georgia);


East Asia (China and Indonesia)


When Lived:


Between about 1.89 million and 70,000 years ago


Eugène Dubois, a Dutch surgeon, first found a Homo erectus (Trinil 2) in Indonesia in 1891. In 1894, DuBois named the species Pithecanthropus erectus, or ‘erect ape-man.’ No hyman fossils were discovered yet in Africa at that time and erectus was the most primitive and small brained specie of all known early human species. One of the first fossil discoveries from Java (beginning in the 1890s) and China (‘Peking Man’, beginning in the 1920s) are the classic examples of Homo erectus species. They are most likely the first species to have expanded beyond Africa, Homo erectus shows high variability, spread over two continents (we don’t know for sure if they reached Europe), and possibly the longest lived early human species - about nine times as long as our own species, Homo sapiens, has been around. Homo erectus fossils were discovered in the Middle Awash region of the Afar Rift in eastern Ethiopia, where from half Ma to more than six Ma human ancestor fossils were found.


Richard Erskine Frere Leakey, second son of Louis and Mary, was born on December 19, 1944. He participated in his parent’s field expeditions from an early age and was therefore well-placed to inherit their legacy. Together with a team from the NMK, Richard led the first expedition to Koobi Fora in 1968. Between 1968 and 1989 he coordinated the NMK field expeditions to the eastern and western shores of Lake Turkana. With the team of talented and experienced fossil hunters led by Mr. Kamoya Kimeu, many important finds were made, including early stone age tools dating to around 1.9 million years old, evidence of early members of the genus Homo, including skulls of Homo habilis and Homo erectus, and remains of robust australopithecines A. boisei and A.aethiopicus. The extraordinary discovery of the nearly complete1.6 million year old skeleton of the “Nariokotome Boy” (or“Turkana Boy”), a Homo erectus youth, was undoubtedly the most important. After Dr. Leakey was appointed the head of the Kenya Wildlife Services KWS in 1989, he was no longer able to continue with fieldwork, though he remains interested in paleoanthropology. Dr. Leakey’s political career culminated in 1999 when then-president Moi appointed him head of Kenya’s Civil Service and of a so-called “Dream Team” of technocrats assembled from various fields and backgrounds to tackle management, corruption, and reorganization issues within the Kenyan government. He stepped down from this position in 2001, announcing at that time that he was retiring from politics.


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Homo Neanderthalensis 1


Neanderthals were heavily built and very muscled. Their brain volume of 1200 to 1800 cubic centimeters, equal to and even larger than modern human brains. Their weight was 30% more than the modern human’s weight. Their skull and body morphology is different from the modern and archaic Homo sapiens morphology. They were particularly adapted with the midface projecting and ending in large front teeth. The evidence of their skull reconstruction show that they were separate species to modern humans. They had heavy brow ridges, a low sloping forehead and a very large nose. Strong evidence for the difference between humans and Neanderthals can be found in the morphology of the Neanderthal pelvis, which is different to a human pelvis. Neanderthals show adaptation to the cold northern climate, with short limbs and stocky bodies and flourished during a warmer interglacial period. They had a short period of dental growth and reached their adulthood by age 15. Geographically and chronologically dispersed Neanderthals hunted as top-level carnivores. There is also evidence from Gibraltar that when they lived in coastal areas, they exploited marine resources such as mollusks, seals, dolphins and fish. Isotopic chemical analyses of Neanderthal bones also tell scientists the average Neanderthal’s diet consisted of a lots of meat. Scientists have also found plaque on the remains of molar teeth containing starch grains—concrete evidence that Neandertals ate plants. Fossils provide evidence that they moved in small groups possibly occupying areas seasonally and hunting animals such as reindeer. As they did not use bows and arrows, or other projectiles, hunting such big game would have required a group strategy. A wooden spear found in the ribs of an Elephas skeleton at Lehringen (Germany), and a Levallois point embedded an Equus (horse) cervical vertebra from Umm el Tlel (Syria), are both attributed to Neanderthal hunting activity. Their hunting, using eight foot long wooden lances, must have brought them in very close contact with their prey. The Mousterian stone tool industry of Neanderthals is characterized by sophisticated flake tools that were detached from a prepared stone core. This innovative technique allowed flakes of predetermined shape to be removed and fashioned into tools from a single suitable stone. They used wood, such a spears, and regularly used fire. Their bones are thick and heavy, and show signs of powerful muscle attachments. Neandertals would have been extraordinarily strong by modern standards.


Height:


Males: average 5 ft 5 in (164 cm); Females: average 5 ft 1 in (155 cm)


Weight:


Males: average 143 lbs (65 kg); Females: average 119 lbs (54 kg)


They show a bit of a sexual dimorphism, however it is not that big as it is seen in earlier humans. Neanderthals used tools for activities like hunting and sewing. Left-right arm asymmetry indicates that they hunted with thrusting spears. A Neanderthal would probably have used a scraper to first clean the animal hide, and then used an awl to poke holes in it, and finally use strips of animal tissue to lace together a loose-fitting garment. Neanderthals were the first early humans to wear clothing, but it is only with modern humans that scientists find evidence of the manufacture and use of bone sewing needles to sew together tighter fitting clothing. Neanderthals controlled fire, lived in shelters, and occasionally made symbolic or ornamental objects. There is evidence that Neanderthals deliberately buried their dead and occasionally even marked their graves with offerings, such as flowers. No other primates, and no earlier human species, had ever practiced this sophisticated and symbolic behavior. They were capable of speaking and probably had language.



The average day for the Neanderthal would start early in the morning, setting up the fire an eating leftovers for breakfast. They were making some tools, if needed and hunting. In their environment they needed a great deal of energy during cold seasons, so getting food would probably be number one priority. They were very socialized, so I presume they spent most of their time in their group, caring about each other, teaching, helping and hunting. During the day they would track down big animals and cook their food at the evening with family.
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Homo Neanderthalensis


Nickname:


Neanderthal


Where Lived:


Europe and southwestern to central Asia


When Lived:


200,000 - 28,000 years ago


The first Neanderthal remains were recognized in Germany in 1856 and presented at a meeting of the Lower Rhine Medical and Natural History Society held in Bonn in February 1857, and named a species, Homo neanderthalensis, by William King in 1864. In 1887, two complete skeletons were found in a cave near Spy in Belgium, and more from sites in France in 1887, 1908 and 1911. Most of these fossils were found in caves. The first Neanderthal skull discovered in modern times hid in a cave in Engis, Belgium until a local doctor Phillipe-Charles Schmerling pulled it out in 1829. It was the crania of a 2-3 year old Neanderthal child, however it was not recognized as such until 1936. Neanderthals occupied Europe from about 800,000 to 30,000 years ago.


1848: Forbes Quarry, Gibraltar: discovery of a skull. One of most complete Neanderthal crania ever found, it was recognized in 1863 by George Busk as similar in form to the skull from the Neander Valley.


1856: Feldhofer Grotto, Neander Valley, Germany: Johann Karl Fuhlrott first recognizes the fossil called “Neanderthal man.”


1866: Trou de La Naulette Cave, Belgium: Edouard Dupont discovers a mandible (lower jaw), ulna (one of two forearm bones) and metacarpal (hand-bone) in association with bones of extinct animals. First Neanderthal remains to be generally accepted as of great antiquity and different anatomy than modern humans.


1874: Pontnewydd, Wales: Discovery of Neanderthal fossils.


1876: Rivaux, S. France: Discovery of Neanderthal fossils.


1880: Šipka, Moravi: Karel Maška. The lower jaw or mandible of a Neanderthal child was found in a secure context, associated with cultural debris, including hearths, Mousterian tools, and bones of extinct animals.


1886: Betche-aux-Rotches cave, Spy d'Orneau, Belgium: Marcel de Puydt & Max Lohest find two nearly complete Neanderthal skeletons in association with Mousterian tools. The publication of these remains established Neanderthals as a separate type of ancient human, rather than pathological modern humans. Unfortunately, the limb-bones were misinter- preted as indicating that Neanderthals walked with bent knees in an ape-like posture.



This is a list of archeological sites where remains and/or tools of Neanderthals were found.
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