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Descent of Man In this lecture, beginners can familiarize themselves with basic information and terms used to describe the evolution of humanity beginning with the origin of primates through the comings and goings of Genus Homo. |
Where We Come From
Posted: Monday, January 29, 2001
(US News) Recent advances in genetics are starting to illuminate the wanderings of early humans
Andy Carvin is a pioneer on the strange frontier of DNA genealogy. The 29-year-old Internet policy analyst had built his family tree back to ancestors in Busk, Ukraine, but that's where the trail went cold. Then he read about research tracing the Y sex chromosome, which is passed intact from father to son, all the way back to the time of Aaron, the single progenitor of the priestly cohen caste 3,000 years ago. More than once, his father had told him their family was cohanim. "I was really curious," Carvin says, "to see if there was even a small possibility that the oral tradition was true." More
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Posted: Sunday, January 21, 2001
In anthropology, the Paleolithic Period, or the Old Stone Age, is the name given to the earliest period of human development and the longest phase of human history, beginning about 2 million years ago and ending between 40,000 and 10,000 years ago, depending on geographic location.
The period between 40,000 and 10,000 years ago is called the Upper Paleolithic Period, and our knowledge of the people of this period is derived from analysis of fossil remains, and artifacts and fragments of artifacts found in association with fossils. With radiocarbon dating techniques, it is often possible to fix the date of any stratum in which fossils and artifacts are found to within one or two thousand years, which provides us with a rough calendar for the history of Paleolithic groups of humans. More
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First Analysis Of Dna From A Neanderthal Bone Posted: Sunday, January 21, 2001
About 10 kilometers east of Dusseldorf in Germany, in the valley of the Dussel, there is a little town called Neander. One hundred and forty-one years ago, in the summer of 1856, some workmen broke into a cave to get at the limestone inside and discovered a set of ancient bones.
Most of the bones were smashed to bits by the workmen, but some of the bones, including part of the skull, survived, and the skeleton was soon recognized by anthropologists as belonging to an ancient race of men who came to be known as the Neanderthals.
A Neanderthal fossil had actually been discovered some years earlier in Gibraltar, but not recognized as such. Neanderthal-like fossils have also been found in France, Spain, Italy, Yugoslavia, Iraq, China, Java, and Israel. More
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Y Chromosome Indicates African Origins Of Man Posted: Sunday, January 21, 2001
The Y chromosome is one of the two chromosomes that determine sex in many animals, including humans, and it carries mostly male- specific genes.
Genetic polymorphisms are individual functional variations of specific genes or genetic markers that occur in a population with a significant frequency, e.g., more than 1%. Mitochondrial DNA (sometimes denoted as mtDNA), found in the mitochondria of all eukaryotes, is believed to evolve in parallel with nuclear DNA, but since sperm lose their mitochondria, it is inherited only in the maternal lineage in animals.
Until now, it has been mitochondrial DNA that has been greatly exploited in studies of the evolution of humans. More
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Personality Trait May Influence Immune System Posted: Friday, January 19, 2001
Individuals may vary in how well they can protect themselves from illness, depending on personality traits as well as on physiological differences, suggest the results of a preliminary study.
Anna L. Marsland, PhD, RN, of the Behavioral Medicine Program at the Western Psychiatric Institute and Clinic at the University of Pittsburgh School of Medicine, in Pennsylvania, and colleagues tested how 84 study participants responded to a vaccine for the viral infection known as hepatitis B. This vaccination prompts the immune system to mount a defense by introducing a tiny amount of the infectious agent into the body. More
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Divergence Of Species In A Warbler’s Song Posted: Friday, January 19, 2001
Biologists at the University of California, San Diego have demonstrated, in a study of the songs and genetics of a series of interbreeding populations of warblers in central Asia, how one species can diverge into two.
Their description of the intermediate forms of two reproductively isolated populations of songbirds that no longer interbreed is the "missing evidence" that Darwin had hoped to use to support his theory of natural selection, but was never able to find. More
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Right Side Of Brain: Key To Recognizing Yourself Posted: Thursday, January 18, 2001
The right side of the brain helps people recognize themselves in a picture, say researchers at Beth Israel Deaconess Medical Center in Boston.
The study joins a growing body of evidence that demonstrates the right hemisphere plays an important role in self-awareness, which scientists believe is one aspect of human consciousness. The research is published in the Jan. 18 issue of the weekly journal Nature. More
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Precocious Earth Posted: Wednesday, January 17, 2001
Scientists are drawing a portrait of how Earth looked soon after it formed 4.56 billion years ago, based on clues within the oldest mineral grains ever found.
Tiny zircons (zirconium silicate crystals) found in ancient stream deposits indicate that Earth developed continents and water -- perhaps even oceans and environments in which microbial life could emerge -- 4.3 billion to 4.4 billion years ago, remarkably soon after our planet formed. More
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More Than 150 Rapidly Moving Stars in the Milky Way Posted: Monday, January 8, 2001
SAN DIEGO, Calif.--Astronomers have found 154 rapidly moving stars towards the center of our galaxy and our brightest neighboring galaxy. The findings are being presented today by Dr. Andrew J. Drake of the Lawrence Livermore National Laboratory for the Massive Compact Halo Objects (MACHO) collaboration, during the annual meeting of the American Astronomical Society in San Diego, Calif.
The results are of special interest because this is the first time scientists have been able to discover such objects in front of the millions of stars seen at the Galactic center and our brightest neighbor galaxy, the Large Magellanic Cloud (LMC).
To date, among the thousands of known High Proper Motion (HPM) stars, few have been discovered in the most densely packed regions of the sky, where stars appear to merge together in images because of their extreme density.
``Until now astronomers have been unable to detect HPM stars in the most dense locations because of the extreme density of stars towards the Galactic center,'' said Drake, who works at Livermore’s Institute for Geophysics and Planetary Physics. "Toward the Galactic center, the billions of stars within our galaxy form the bright band in the sky known as the Milky Way."
Another region where the density of stars makes discovery of the moving ones difficult is towards the LMC. To the naked eye this galaxy appears as a faint nebulous patch in the southern sky. Through a small telescope the presence of millions of individual stars becomes recognizable.
Our solar system resides 26,000 light years from the center of the galaxy and rotates once every 240 million years. The great distance to the Galactic center means that the slow rotation of the Sun has little effect on stars there. However, much closer stars (less than 500 light years) appear to move relative to these distant stars. In order to find HPM stars, Drake looked at images of stars in the Galactic center and the LMC taken over seven years.
Using 50 thousand astronomical images of 55 million stars, Drake identified the stars that appear to move and measured their motions. From these measurements, he discovered 154 new HPM stars. The yearly motions of these objects are estimated to be accurate to 6 milli-arcseconds, which is equivalent to the width of a human hair seen from a distance of a mile.
These images came from a recent galactic dark matter experiment using the 50-inch Great Melbourne Telescope in Canberra, Australia. During the 1990s, scientists also used the Great Melbourne Telescope to detect MACHOs (Massive Compact Halo Objects) through the gravitational microlensing of stars. Microlensing is a physical phenomenon which causes starts to appear to shift of brighten when two or more of them lie on the same line of sight.
Over the years, techniques such as astrometry have allowed astronomers to produce a picture of the motions of stars within our galaxy. Astrometry is the branch of astronomy that deals with the measurement of positions and movements. Applying this picture to the motions of the HPM stars discovered, Drake was able to predict that most of these objects likely are located at distances between 100 and 1000 light years. However, at present, the motions of these newly discovered HPM stars have been based on the motion measured between just two images. More detailed studies of these stars are necessary to determine if they are very nearby, how the parallax effect, due to the Earth’s motion around the Sun, would change the true direction of each HPM star’s motion from that observed.
Although many microlensing events have been discovered, astronomers continue to search for them because they can point out properties of the lensing objects, such as planets, which populate our galaxy. Within the next ten years, NASA's Space Interferometry Mission (SIM) telescope will be launched into orbit. One of the goals of this mission is to use astrometry to determine the masses and distances of the stars causing microlensing events. By finding the HPM stars in the foreground of these dense areas of the sky and predicting their paths over future years, astronomers will be able determine when these stars will pass in front of a distant star to cause microlensing. More
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