Human

Where Lived: Evolved in Africa, now worldwide When Lived: About 200,000 years ago to present The species that you and all other living human beings on this planet belong to is Homo sapiens. During a time of dramatic climate change 200,000 years ago, Homo sapiens (modern humans) evolved in Africa. Like other early humans that were living at this time, they gathered and hunted food, and evolved behaviors that helped them respond to the challenges of survival in unstable environments. Anatomically, modern humans can generally be characterized by the lighter build of their skeletons compared to earlier humans. Modern humans have very large brains, which vary in size from population to population and between males and females, but the average size is approximately 1300 cubic centimeters. Housing this big brain involved the reorganization of the skull into what is thought of as "modern" -- a thin-walled, high vaulted skull with a flat and near vertical forehead. Modern human faces also show much less (if any) of the heavy brow ridges and prognathism of other early humans. Our jaws are also less heavily developed, with smaller teeth. Scientists sometimes use the term “anatomically modern Homo sapiens” to refer to members of our own species who lived during prehistoric times.

Fossils and DNA confirm humans are one of more than 200 species belonging to primates. Within that larger group, humans are nested within the great ape family. Although we did not evolve from any of the apes living today, we share characteristics with chimpanzees, gorillas, and orangutans (the great apes), as well as other apes. We most likely evolved from Homo heidelbergensis, the common ancestor we share with Neanderthals, who are our closest extinct relatives.

Unlike every other human species, Homo sapiens does not have a true type specimen. In other words, there is not a particular Homo sapiens individual that researchers recognize as being the specimen that gave Homo sapiens its name. Even though Linnaeus first described our species in 1758, it was not customary at that time to designate type specimens. It is rumored that in 1994 paleontologist Robert Bakker formally declared the skull of Edward Drinker Cope as the “lectotype”, a specimen essentially serving as the type specimen. When Cope, himself a great paleontologist, died in 1897, he willed his remains to science, and they are held by the University of Pennsylvania. But a type specimen must be one examined by the original author who names a species, so Cope’s remains do not qualify.

Prehistoric Homo sapiens not only made and used stone tools, they also specialized them and made a variety of smaller, more complex, refined and specialized tools including composite stone tools, fishhooks and harpoons, bows and arrows, spear throwers and sewing needles. For millions of years all humans, early and modern alike, had to find their own food. They spent a large part of each day gathering plants and hunting or scavenging animals. By 164,000 years ago modern humans were collecting and cooking shellfish and by 90,000 years ago modern humans had begun making special fishing tools. Then, within just the past 12,000 years, our species, Homo sapiens, made the transition to producing food and changing our surroundings. Humans found they could control the growth and breeding of certain plants and animals. This discovery led to farming and herding animals, activities that transformed Earth’s natural landscapes—first locally, then globally. As humans invested more time in producing food, they settled down. Villages became towns, and towns became cities. With more food available, the human population began to increase dramatically. We have been so successful that we have inadvertently created a turning point in the history of life on Earth. Modern humans evolved a unique combination of physical and behavioral characteristics, many of which other early human species also possessed, though not to the same degree. The complex brains of modern humans enable us to interact with each other and with their surroundings in new and different ways. As the environment became more unpredictable, bigger brains helped our ancestors survive. We make specialized tools, and use tools to make other tools, as described above; we eat a variety of animal and plant foods and ; we have control over fire; we live in shelters; we build broad social networks, sometimes including people we have never even met; we exchange resources over wide areas; and we create art, music, personal adornment, rituals, and a complex symbolic world. Modern humans have spread to every continent and vastly expanded our numbers. We have altered the world in ways that benefit us greatly. But this transformation has unintended consequences for other species as well as for ourselves, creating new survival challenges.

Cro-Magnon 1 Nickname: Cro-Magnon Man Site: Cro-Magnon, France Date of discovery: 1868 Discovered by: Louis Laret Age: About 30,000 years old Species: Homo sapiens Historic Homo sapiens Discovered in 1868, the Cro-Magnon 1 was among the first fossils to be recognized as belonging to our own species—Homo sapiens. This famous fossil skull is from one of several modern human skeletons found at the famous rock shelter site at Cro-Magnon, near the village of Les Eyzies, France. Road construction in 1868 revealed the rock shelter tucked into a limestone cliff. Researchers recognized an occupation floor toward the back of the cave during excavations. The occupation area revealed the remains of four adult skeletons, one infant, and some fragmentary bones. The condition and placement of ornaments, including pieces of shell and animal teeth fashioned into what appear to be pendants or necklaces, led researchers to believe the skeletons had been intentionally buried within the shelter in a single grave. The site was one of the first to establish the ancient roots of modern humans, and fossils from this shelter represent some of the oldest Homo sapiens populations of Europe. Associated tools and fragments of fossil animal bone date the site to the uppermost Pleistocene, probably between 32,000 and 30,000 years old. Cro-Magnon 1 is a middle-aged, male skeleton of one of the four adults found in the cave at Cro-Magnon. Scientists estimate his age at death at less than 50 years old. Except for the teeth, his skull is complete, though the bones in his face are noticeably pitted from a fungal infection. While the Cro-Magnon remains are representative of the earliest anatomically modern human beings to appear in Western Europe, this population was not the earliest anatomically modern humans to evolve - our species evolved about 200,000 years ago in Africa. however, the skull of Cro-Magnon 1 does show the traits that are unique to modern humans, including the tall, rounded skull with a near vertical forehead. A large brow ridge, no longer tops the eye sockets andthere is no prominent prognathism of the face and jaw. Analysis of the skeletons found at the rock shelter indicates that the humans of this time period led a physically tough life. In addition Cro-Magnon 1’s fungal infection, several of the individuals found at the shelter had fused vertebrae in their necks indicating traumatic injury, and the adult female found at the shelter had survived for some time with a skull fracture. The survival of the individuals with such ailments is indicative of group support and care, which allowed their injuries to heal. Skhul V Site: Mount Carmel, Israel Date of discovery: 1932 Discovered by: Theodore McCown and Hallam L. Movius, Jr. Age: Between 120,000 and 80,000 years old Species: Homo sapiens Skhūl V was recovered from the Skhūl Cave near Mount Carmel, Israel, along with the skeletons of nine other adults and children. Some anatomical features, like the brow ridges above the eyes of the male Skhūl V skull are reminiscent of earlier humans; however, Skhūl V also has the high, vertical forehead and rounded skull typical of modern human skulls. At the back of the skull, Skhūl V also lacks a projecting ‘bun,’ which occurs in many Neanderthal skulls. The Skhūl site was originally thought to be about 40,000 years old based on a comparison of animal remains and stone tools found at the site with those from other archeological sites in the region. This late date was important since it was then assumed that the Neanderthal fossils found at the nearby fossil site of Tabun Cave must be older than the modern Homo sapiens population of Skhul. This assumption left open the possibility that the Tabun Neanderthals were the evolutionary ancestors of modern humans at Skhūl. However, after more precise dating techniques, scientists found that the modern Homo sapiens fossils at Skhūl were about 90,000 years old, much older than was previously thought. This meant the anatomically modern human population at Skhūl lived at the same time as the Neanderthal population of Tabun. Therefore, the Tabun Neanderthals could not have been the ancestors of modern humans in the Near East. 3-D collection link: http://humanorigins.si.edu/evidence/3d-collection/f-skh%C5%ABl-v

There are several different kinds of immune system cells. Below is an in-depth description of what they are and do:

T lymphocyte cell

There are two types of T lymphocyte cell. The first one is the CD4+ T Cell, also known as the T helper. The job of the CD4+ T Cell is to secrete special chemicals that activate the other ImmuneSystem Cells (immune cells). CD4+ T Cells are the most importantcells in the immune system of the human body.

The other type of T lymphocyte is the CD8+ T Cell, also known as the T killer cell. The T killer cell killstumor cells and virus-infected cells. The CD8+ TCell, along with the Natural Killer Cell, protects the body from threats that cannot be combated directly.

Natural Killer Cells

Natural killer cells, also known asNK cells, performs the same role as the CD8+ T Cell, except that it performs its role with or without secretions from the CD4+ T Cells.The natural killer cells fuction as a back-up in the face of heavy cancer or HIV. This allows the human body to continue to live for a while longer even after the CD4+ T Cells communication system has collapsed.

B cells

The role of a B cell is to manufacture antibodies. This is crucial because antibodies mark a pathogen for destruction. Because of this, B cells are the second most important cell in the immune system.

Granulocytes

Granulocytes are tied in importance with the B cells. Even though it is important to mark pathogens for destruction, it is also vital to have some cells to actually destroy the pathogen.

There are three types of granulocytes: neutrophils, eosinophils, and basophils. All three types of granulocytes gobble up bacteria. But basophils also play a role in allergies, and neutrophils occasionally help with eating up tumors.

In short, granulocytes make up the bulk of the immune system.

Macrophages

Macrophages are important cells. Their role is to pick up foreign materials and present the antigens to CD4+ T Cells or B cells. This is the beginning of the immune process. However, macrophages are not that important because there is another type of cell called a dendrite that does the same work the macrophages do.

Dendritic cells

Another cell type, adressed only recently, is the dendritic cell. As stated above, dendritic cells perform the same role that macrophages do. They are in fact, better at presenting antigens because they are faster and consume less energy. However, there is a downside.

The downside is that dendritic cells bind a high amount of HIV virus. During an activation event, dendritic cells transmit HIV to the CD4+ T Cells, which leads to collapse of the immune system.

Pretty much all of human behavior comes from our brains, and ultimately our neurons.

There are four types of neurons:

The bipolar neuron (interneuron), the unipolar neuron (sensory neuron), the multipolar neuron (motor neuron) and finally the pyramid cell.

Neurons have a great diversity of lenghts. The shortest neurons are less than 1 millimeterlong and the longest neurons up toa meter long!

Neurons have three crucial parts: the soma, the dendrites and the axon. The soma is where the nucleus and the cell proper of the neuron is. The dendrites recieve information from other neurons and transmit it to the soma. The axon is the "talker" sending information from the soma of the neuron to other neurons. The axon is long and thin, makes up most of the neurons length and depending what type of neuron the cell is, the axon could be encased in a "protective layer of fat called the Myelin Sheath". In contrast, dendrites are numerous, fat and bushy.

If the Myelin Sheath is broken or worn out, people get a mental condition called Multiple Sclerosis. Eventually,a worn out Myelin Sheath leads to total loss of muscle control.

When the soma of a neuron wants to send a message, it fires an electric current down the axon and thensecretes special chemicals to breach a gap between the two neurons called a synaptic gap. The synaptic gap is only one millionth of an inch wide, so it is relatively easy to breach.

There are many different chemicals in the brainthat trigger or calm down neurons.