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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. |
Life's leap to land
Posted: Thursday, November 30, 2000
Life made the transition to land more than a billion years earlier than previously thought, according to new geological evidence.
Organic material discovered within South African rocks suggests that microbes made the leap from the oceans to land about 2.6 billion years ago. Until now, 1.2 billion-year-old fossils of blue-green algae found in Arizona contained the earliest record of terrestrial life. The discovery gives scientists new information about the presence of life-sustaining oxygen in the Earth's atmosphere. An ozone shield and an oxygen rich atmosphere around the planet would have been needed for life on land to emerge. The rocks come from what is now the Eastern Transvaal district of South Africa. They contain fossilised remnants of mats of photosynthetic bacteria, organisms that generate oxygen from water and atmospheric carbon dioxide.
"This places the development of terrestrial biomass more than 1.4 billion years earlier than previously reported," said Yumiko Watanabe, of the Pennsylvania State University, US, in the scientific journal Nature. More
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Posted: Wednesday, November 29, 2000
(BBC) Scientists have taken a virtual tour inside several ancient Egyptian mummies.
The researchers used computed tomography (CT) imaging to produce extraordinary images of the embalmed individuals and reveal details of how they might have lived and died.
"It's like exploring the insides of the mummies with a camera, without unwrapping them or destroying them in any way,'' said Dr Heidi Hoffman, of Emory University Hospital in Atlanta, US, who headed the study.
One of the images provides a tour inside the rib cage of a mummy believed to be that of Ramesses I, the first pharaoh of the 19th dynasty during ancient Egypt's splendid New Kingdom period, who died in about 1314 BC.
It shows abdominal organs tightly rolled in linen packs as was then the embalming custom.
Another image from the same mummy shows a severely deformed ear, perhaps the result of a bad piercing job, and a skull full of embalming resin. More
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Adam and Eve never met, scientists say Posted: Wednesday, November 15, 2000
(CNN) WASHINGTON (Reuters) -- Science may have caught up with the Bible, which says that Adam and Eve are the ancestors of all humans alive today.
But in the scientists' version, based on DNA analysis, "Adam," the genetic ancestor of all men living today, and "Eve," the genetic ancestor of all living women, seem to have lived tens of thousands of years apart.
How could this be?
Peter Underhill and colleagues at Stanford University in California have an explanation. "They had different molecular clocks," Underhill said in a telephone interview. "Fewer men participated in reproduction than women did."
His team, working with top geneticists across the United States, Europe, Israel and Africa, did a genetic analysis of DNA samples from the Y chromosomes of more than 1,000 men from 22 geographic areas and determined that their most recent common ancestor was a man who lived in Africa around 59,000 years ago.
Only men have Y chromosomes and researchers can look at gradual genetic mutations in them to "count" generations.
Other studies have used mitochondrial DNA, which women seem to pass down virtually unchanged from mother to daughter, to show that the genetic "Eve" lived 143,000 years ago.
The latest study, published in the November issue of the journal Nature Genetics, reconciles the two findings, and in the process the researchers came up with new tool for looking at how people are different from one another genetically. More
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Study Boosts 'Out of Africa' Theory Posted: Sunday, November 12, 2000
(Discovery) A study of mutations in the Y chromosome confirms the theory that modern humans originated in Africa and then spread out across the world. More significantly, the study proves the Y chromosome, which all men inherit from their fathers, to be a powerful tool for following human migration.
Peter Underhill of Stanford University and his colleagues based their conclusions on detailed analysis of DNA from more than 1000 men in 22 different geographic areas. Their work appears in the current issue of Nature Genetics. More
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