Ten million-year-old fossils discovered in Ethiopia show that humans and apes probably split six or seven million years earlier than widely thought, according to landmark study released Wednesday.
The handful of teeth from the earliest direct ancestors of modern gorillas ever found -- one canine and eight molars -- also leave virtually no doubt, the study's authors and experts said, that both humans and modern apes did indeed originate from Africa.
The near total absence to date of traces on the continent of apes from this period had led many scientists to conclude that the shared line from which humans and living great apes emerged had taken a long evolutionary detour through Eurasia.
The Last common ancestor - out of Africa
But the study, published in the British journal Nature, demonstrates that the Last Common Ancestor (of both man and ape) was strictly an African phenomenon. Tthe fossils are viewed as "a critically important discovery," a view echoed by several other scientists who had read the paper or seen the artifacts.
The most startling implication of the find, the scientists agree, is that our human progenitors diverged from today's great apes -- including gorillas, orangutans and chimpanzees -- several million years earlier than widely accepted research based on molecular genetics had previously asserted.
The trail in the hunt for physical evidence of our human ancestors goes cold some six or seven million years ago.
The anthropological past
Orrorin was discovered in Kenya in 2000 and nicknamed "Millennium Man" and it goes back 5.8 to 6.1 million years, while Sahelanthropus, found in 2001 later in Chad, is considered by most experts to extend the human family tree another one million years into the past.
Beyond that, however, fossils of early humans from the Miocene period, 23 to five million years ago, disappear. Fossils of early apes especially during the critical period of 14 to eight million years ago were virtually non-existant -- until now.
"We know nothing about how the human line actually emerged from apes," the authors of the paper noted.
But the new fossils, dubbed "Chororapithecus abyssinicus" by the team of Japanese and Ethiopian paleoanthropologists who found them, place the early ancestors of the modern day gorilla 10 to 10.5 million years in the past, suggesting that the human-ape split occurred before that.
The line: Orangutan, Gorrilla, Chimpanzee - Human
There is broad agreement that chimpanzees were the last of the great apes to split from the evolutionary line leading to man, after gorillas and, even earlier, orangutans.
Conventional scientific wisdom, based on genetic "distances" measured by molecular geneticists, had placed the divergence between chimps and humans some five to six million years ago. Orangutans are thought to have parted company with our ancestors 13 to 14 million years ago.
"If the new discovery is in the gorilla lineage, then this will definitely substantially push back the split time between apes and humans," Halie-Selassie at Kent State told AFP.
When did the split take place?
The scientists leading the team that found the fossils calculated that the human-orangutan split could easily have been as old as 20 million years.
They determined that the teeth belonged to gorilla ancestors based on unique shared characteristics of the molars, which had evolved for a diet of fibrous foods such as stems and leaves.
The match is not exact, however, and could prompt some scientists to challenge the findings.
The teeth fragments, found in barren scrubland some 170 kilometres (100 miles) east of Ethiopia's capital Addis Ababa, almost went unnoticed.
Asfaw recalled the chance discovery.
"It was our last day of field survey in February 2006, and our sharp-eyed field assistant, Kampiro, found the first ape tooth, a canine," he said.
"He picked it up and showed it to me, and I knew that this was something new -- Ethiopia's first fossil great ape."
Wednesday, August 22, 2007
Tuesday, August 21, 2007
How close are we to creating artificial life?
Around the world, a few scientists are trying to create life from scratch ...they're getting closer.
Some experts expect an announcement within 3 to 10 years from someone in the now little-known field of "wet artificial life."
That first cell of synthetic life—made from the basic chemicals in DNA— i.e., creating protocells has the potential to shed new light on our place in the universe, this will remove one of the few fundamental mysteries about creation in the universe and our role.
His idea is that once the container is made, if scientists add nucleotides in the right proportions, then Darwinian evolution could simply take over. It's a cleaver ploy we may not be smart enough to design things, but we let evolution do the hard work and then we figure out what happened.
One scientist is attacking that problem by going outside of natural genetics. Normal DNA consists of four bases—adenine, cytosine, guanine and thymine (known as A,C,G,T)—molecules that spell out the genetic code in pairs. Instead of 4 pair, one scientist is trying to add eight new bases to the genetic alphabet.
Some experts expect an announcement within 3 to 10 years from someone in the now little-known field of "wet artificial life."
That first cell of synthetic life—made from the basic chemicals in DNA— i.e., creating protocells has the potential to shed new light on our place in the universe, this will remove one of the few fundamental mysteries about creation in the universe and our role.
It's going to be a big deal and everybody's going to know about it, we're talking about a technology that could change our world in pretty fundamental ways—in fact, in ways that are impossible to predict.
Several scientists believe man-made life forms will one day offer the potential for solving a variety of problems, from fighting diseases to locking up greenhouse gases to eating toxic waste.
Bedau figures there are three major hurdles to creating synthetic life:
- A container, or membrane, for the cell to keep bad molecules out, allow good ones, and the ability to multiply.
- A genetic system that controls the functions of the cell, enabling it to reproduce and mutate in response to environmental changes.
- A metabolism that extracts raw materials from the environment as food and then changes it into energy.
His idea is that once the container is made, if scientists add nucleotides in the right proportions, then Darwinian evolution could simply take over. It's a cleaver ploy we may not be smart enough to design things, but we let evolution do the hard work and then we figure out what happened.
One scientist is attacking that problem by going outside of natural genetics. Normal DNA consists of four bases—adenine, cytosine, guanine and thymine (known as A,C,G,T)—molecules that spell out the genetic code in pairs. Instead of 4 pair, one scientist is trying to add eight new bases to the genetic alphabet.
Monday, August 20, 2007
DNA Replication Behavior- from Low to High
DNA replication is considered the heart of the DNA process. Recent findings by scientists at the Genome Institute of Singapore (GIS) may be paving the way for more efficient analyses and tests related to the replication of cells, and ultimately, to the better understanding of human biology, such as in stem cell research.
Where does duplication occur?
Faithful duplication of the genome ensures that daughter cells inherit a complete set of genetic materials identical to parent cells. This duplication occurs in the section of the cell cycle known as the S-phase. Extensive research on the budding yeast revealed that the replication process is started at hundreds of origins in the S-phase.
Is the replication process efficient?
Many previous studies focused on the replication timing and initiation sites, but not on the efficiency. So it was believed that the replication efficiency decreased as the S-phase progressed.
But now they know better. In a recently published paper scientists described how they were able to determine the replication timing and efficiency at the various loci in the genome. Now replication efficiency is low at the beginning of the S-phase, but the efficiency increased at the later stage of this phase.
Where does duplication occur?
Faithful duplication of the genome ensures that daughter cells inherit a complete set of genetic materials identical to parent cells. This duplication occurs in the section of the cell cycle known as the S-phase. Extensive research on the budding yeast revealed that the replication process is started at hundreds of origins in the S-phase.
Is the replication process efficient?
Many previous studies focused on the replication timing and initiation sites, but not on the efficiency. So it was believed that the replication efficiency decreased as the S-phase progressed.
But now they know better. In a recently published paper scientists described how they were able to determine the replication timing and efficiency at the various loci in the genome. Now replication efficiency is low at the beginning of the S-phase, but the efficiency increased at the later stage of this phase.
Sunday, August 19, 2007
Genes changes linked to an organism's survivability
Studies from biologists have found that a simple interaction between just two genes determines the patterns of fur coloration that camouflage mice against their background, protecting them from many predators. The work marks one of the few instances in which specific genetic changes have been linked to an organism's ability to survive in the wild.
What does the research show?
The work shows how changes in just a few genes can greatly alter an organism's appearance. It also illuminates the pathway by which these two genes interact to produce distinctive coloration. The result is that now there's reason to believe this simple pathway may be evolutionarily conserved across mammals that display lighter bellies and darker backs, from mice to tuxedo cats to German Shepherds.
What was studied?
Researchers studied Peromyscus, a mouse that is the most widespread mammal in North America. Within the last several thousand years, these mice have migrated from mainland Florida to barrier islands and dunes along the Atlantic and Gulf coasts, where they now live on white sand beaches. In the process, the beach mice's coats have become markedly lighter than that of their mainland brethren.
What did the research show?
Nature provides a tremendous amount of variation in color patterns among organisms, ranging from leopard spots to zebra stripes; these patterns help individuals survive. But it has been difficult to understand how these adaptive color patterns are generated. The research helped identify the genetic changes producing a simple color pattern that helps camouflage mice inhabiting the sandy dunes of Florida's Gulf and Atlantic coasts. These 'beach mice' have evolved a lighter pigmentation than their mainland relatives, a coloration that helps camouflage them from predators that include owls, herons, and hawks.
Previous research has shown that such predators, all of which hunt by sight, will preferentially catch darker mice on the white sand beaches, providing a powerful opportunity for natural selection to evolve increased camouflage.
Which Genes were involved?
Through a detailed genomic analysis, researchers identified two pigmentation genes, for the melanocortin-1 receptor (Mc1r) and an agouti signaling protein (Agouti) that binds to this receptor and turns it off. Conclusion: A single amino-acid mutation in Mc1r gene can weaken the receptor's activity, or a mutation in the Agouti gene can increase the amount of protein present without changing the protein's sequence, also reducing Mc1r activity and yielding lighter pigmentation.
Research findings
What do the genes do? Both genes affect the type and amount of melanin in individual hairs. If both genes are turned on, the mouse is dark in color. If a mutation occurs, which changes either gene this leads to a somewhat blonder mouse, but when the combination of mutations occur in both genes this produces a mouse very light in color.
What does the research show?
The work shows how changes in just a few genes can greatly alter an organism's appearance. It also illuminates the pathway by which these two genes interact to produce distinctive coloration. The result is that now there's reason to believe this simple pathway may be evolutionarily conserved across mammals that display lighter bellies and darker backs, from mice to tuxedo cats to German Shepherds.
What was studied?
Researchers studied Peromyscus, a mouse that is the most widespread mammal in North America. Within the last several thousand years, these mice have migrated from mainland Florida to barrier islands and dunes along the Atlantic and Gulf coasts, where they now live on white sand beaches. In the process, the beach mice's coats have become markedly lighter than that of their mainland brethren.
What did the research show?
Nature provides a tremendous amount of variation in color patterns among organisms, ranging from leopard spots to zebra stripes; these patterns help individuals survive. But it has been difficult to understand how these adaptive color patterns are generated. The research helped identify the genetic changes producing a simple color pattern that helps camouflage mice inhabiting the sandy dunes of Florida's Gulf and Atlantic coasts. These 'beach mice' have evolved a lighter pigmentation than their mainland relatives, a coloration that helps camouflage them from predators that include owls, herons, and hawks.
Previous research has shown that such predators, all of which hunt by sight, will preferentially catch darker mice on the white sand beaches, providing a powerful opportunity for natural selection to evolve increased camouflage.
Which Genes were involved?
Through a detailed genomic analysis, researchers identified two pigmentation genes, for the melanocortin-1 receptor (Mc1r) and an agouti signaling protein (Agouti) that binds to this receptor and turns it off. Conclusion: A single amino-acid mutation in Mc1r gene can weaken the receptor's activity, or a mutation in the Agouti gene can increase the amount of protein present without changing the protein's sequence, also reducing Mc1r activity and yielding lighter pigmentation.
Research findings
What do the genes do? Both genes affect the type and amount of melanin in individual hairs. If both genes are turned on, the mouse is dark in color. If a mutation occurs, which changes either gene this leads to a somewhat blonder mouse, but when the combination of mutations occur in both genes this produces a mouse very light in color.
Does temperature affect evolution?
Where does evolution occur in a temperate area or in a hot area?
It turns out that new species originate more frequently in temperate regions than in the tropics. Steamy and wet they may be, but tropical hotspots of biodiversity are not the hottest as far as evolution is concerned. Scientists looked at pairs of "sister" species - pairs that evolved from an immediate common ancestor - and estimated how long ago the sisters diverged from each other.
In hot areas
Near the equator, sister species split on average about 3.4 million years ago, whereas those in temperate regions split roughly 1.7 million years ago. It is true that tropical zones do host a greater species diversity, but that's because fewer species have gone extinct there.
In cold areas
In very high latitudes - above the Arctic Circle - the sister species split even more recently, with none of those reviewed separating more than a million years ago.
Dramatic climatic changes in temperate regions over the past hundreds of thousands of years may have driven evolution harder.
It turns out that new species originate more frequently in temperate regions than in the tropics. Steamy and wet they may be, but tropical hotspots of biodiversity are not the hottest as far as evolution is concerned. Scientists looked at pairs of "sister" species - pairs that evolved from an immediate common ancestor - and estimated how long ago the sisters diverged from each other.
In hot areas
Near the equator, sister species split on average about 3.4 million years ago, whereas those in temperate regions split roughly 1.7 million years ago. It is true that tropical zones do host a greater species diversity, but that's because fewer species have gone extinct there.
In cold areas
In very high latitudes - above the Arctic Circle - the sister species split even more recently, with none of those reviewed separating more than a million years ago.
Dramatic climatic changes in temperate regions over the past hundreds of thousands of years may have driven evolution harder.
Friday, August 17, 2007
Retracing Evolution With First Atomic Structure Of An Ancient Protein
Can you show any evidence of evolution by looking at the atomic structure of a protein? Scientists say yes. They have determined for the first time the atomic structure of an ancient protein. This reveals in detail how genes evolved their functions.
Recreating ancient progenitors of protein
The workhorses of the cell are proteins. But a detailed study showing how proteins have evolved has not been possible and has eluded evolutionary biologists. This was due because ancient proteins have not been available for direct study. So scientists used state-of-the-art computational and molecular techniques to re-create the ancient progenitors of an important human protein.
Looking at the Atoms
The challenge: can you use only the atoms of ancient proteins to trace changes in the atomic architecture? Two different groups of scientists worked together to trace how changes in the protein's atomic architecture over millions of years caused it to evolve a crucial new function -- uniquely responding to the hormone that regulates stress.
The ultimate level of detail
This is the ultimate level of detail and you can see exactly how evolution tinkered with the ancient structure to produce a new function that is crucial to our own bodies today.
The researchers focused on the glucocorticoid receptor (GR), a protein in humans and other vertebrates that allows cells to respond to the hormone cortisol, which regulates the body's stress response. The scientists' goal was to understand the process of evolution behind the GR's ability to specifically interact with cortisol.
How it was done
Scientists used computational techniques and a large database of modern receptor sequences to determine the ancient GR's gene sequence from a time just before and just after its specific relationship with cortisol evolved. The ancient genes existed more than 400 million years ago -- were then synthesized, expressed, and their structures determined using X-ray crystallography, a state-of-the art technique that allows scientists to see the atomic architecture of a molecule.
Results
The structures allowed the scientists to identify exactly how the new function evolved. They found that just seven historical mutations, when introduced into the ancestral receptor gene in the lab, recapitulated the evolution of GR's present-day response to cortisol. They were even able to deduce the order in which these changes occurred, because some mutations caused the protein to lose its function entirely if other "permissive" changes, which otherwise had a negligible effect on the protein, were not in place first.
Recreating ancient progenitors of protein
The workhorses of the cell are proteins. But a detailed study showing how proteins have evolved has not been possible and has eluded evolutionary biologists. This was due because ancient proteins have not been available for direct study. So scientists used state-of-the-art computational and molecular techniques to re-create the ancient progenitors of an important human protein.
Looking at the Atoms
The challenge: can you use only the atoms of ancient proteins to trace changes in the atomic architecture? Two different groups of scientists worked together to trace how changes in the protein's atomic architecture over millions of years caused it to evolve a crucial new function -- uniquely responding to the hormone that regulates stress.
The ultimate level of detail
This is the ultimate level of detail and you can see exactly how evolution tinkered with the ancient structure to produce a new function that is crucial to our own bodies today.
The researchers focused on the glucocorticoid receptor (GR), a protein in humans and other vertebrates that allows cells to respond to the hormone cortisol, which regulates the body's stress response. The scientists' goal was to understand the process of evolution behind the GR's ability to specifically interact with cortisol.
How it was done
Scientists used computational techniques and a large database of modern receptor sequences to determine the ancient GR's gene sequence from a time just before and just after its specific relationship with cortisol evolved. The ancient genes existed more than 400 million years ago -- were then synthesized, expressed, and their structures determined using X-ray crystallography, a state-of-the art technique that allows scientists to see the atomic architecture of a molecule.
Results
The structures allowed the scientists to identify exactly how the new function evolved. They found that just seven historical mutations, when introduced into the ancestral receptor gene in the lab, recapitulated the evolution of GR's present-day response to cortisol. They were even able to deduce the order in which these changes occurred, because some mutations caused the protein to lose its function entirely if other "permissive" changes, which otherwise had a negligible effect on the protein, were not in place first.
Thursday, August 16, 2007
In evolutions playground, Humans left chimps behind
What is the difference between humans and chimps?
MICRO-RNA, the snippets of RNA that control gene expression, could be the difference.
Variation between individuals, in traits ranging from pigment to behaviour, is the raw material of evolution. The difference can be down to very subtle changes: the genes involved may code for exactly the same proteins but make them at other places and times. So could micro-RNA be the determining factor?
What do Micro-RNA's do?
Micro-RNAs are a mere 22 nucleotides long and block the messenger RNA that translates DNA into protein. This allows them to fine-tune gene expression. Micro-RNA has only recently been studied because it was discovered withing the last few years. But it has been shown to determine what cell types form, and, for example, whether sheep become muscular or puny.
Now, researchers at the Hubrecht Laboratory in Utrecht, the Netherlands, have combed painstakingly through the RNA in human and chimp brains, and found 447 new micro-RNAs, more than doubling the number discovered so far. Some were expressed very rarely.
What accounts for the differences between Chimps and Humans?
The brain has 10,000 cell types, so it is possible because of all these micro-RNAs. Many were unique to chimps and humans, and some only to humans. So while we share most of our DNA with chimps, the small genetic changes through Micro RNA that fine-tune its expression might account for the radical differences in our brains. This is the playground of evolution.
MICRO-RNA, the snippets of RNA that control gene expression, could be the difference.
Variation between individuals, in traits ranging from pigment to behaviour, is the raw material of evolution. The difference can be down to very subtle changes: the genes involved may code for exactly the same proteins but make them at other places and times. So could micro-RNA be the determining factor?
What do Micro-RNA's do?
Micro-RNAs are a mere 22 nucleotides long and block the messenger RNA that translates DNA into protein. This allows them to fine-tune gene expression. Micro-RNA has only recently been studied because it was discovered withing the last few years. But it has been shown to determine what cell types form, and, for example, whether sheep become muscular or puny.
Now, researchers at the Hubrecht Laboratory in Utrecht, the Netherlands, have combed painstakingly through the RNA in human and chimp brains, and found 447 new micro-RNAs, more than doubling the number discovered so far. Some were expressed very rarely.
What accounts for the differences between Chimps and Humans?
The brain has 10,000 cell types, so it is possible because of all these micro-RNAs. Many were unique to chimps and humans, and some only to humans. So while we share most of our DNA with chimps, the small genetic changes through Micro RNA that fine-tune its expression might account for the radical differences in our brains. This is the playground of evolution.
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