13 Sep '12 09:172 editsI have compiled a series of articles that show how our understanding of lineage and survival-of-the fittest are only aspects to the ongoing forces which are shaping human evolution
The first article gives a brief synopsis of recent human lineage and a more detailed explanation how the pure chaos of interacting lineages makes the concept of a 'missing link' non-sensical.
The second two articles give a fascinating insight into forces other than 'natural selection' that have played a crucial role in the evolution of man's cognitive prowess and dextrous abilities.
HAR elements (Human Accelerated Regions) are highly conserved non-coding regions that underwent rapid evolution about 4 million years ago (the time equated with the emergence of homo-erectus).
The studies involved show how there was very limited adaptation of these elements before the split between humans and chimpanzees. The following period saw a period of rapid evolution, driven
by 'fertile' regions of DNA and a strong push toward G-C based preferential bonding. The hypothesis involves an 'emergence' time when preferential adaptivity would create immediate, disparate
differences in cognitive ability within hominid populations.
The final article deals with more recent human developments due to the partial duplication of a SRGAP2 gene involved in neuronal migration and plasticity.
It is believed that a recent relaxation in selective pressures allowed fixation of alleles to partially mimic the action of adaptive evolution.
EARLIEST MEN, HOMINIDS AND APES
There are two major groups, or genera of hominids: Australopithecus , which lived between 4 million and 1 million years ago and includes a number of species; and Homo , which appeared around
2.5 million years ago and includes, Homo habilis , Homo erectus and Homo sapiens (modern man).
Research by geneticist in the mid 2000s determined that the human genome and chimpanzees are only different by 1.23 percent. The one small percentage difference encompasses 35 million individual
chemical changes accumulated over the 5 million to 7 million years during which the species evolved apart. Put another way humans and chimpanzees share 98.77 percent of the same genetic material.
The study of early man has often been posed as a quest for “the missing link.” Most scientists bristle at the term. Tim White, a paleoanthropologist at the University of California, Berkeley,
told National Geographic, “The term is wrong in so many ways, it’s hard to know where to begin. Worst all is the implication that at some point there existed something halfway between chimp and
human. That’s a popular misconception that has plagued evolutionary science from the beginning.”
New discoveries have also debunked theories that human evolution was marked by a series of nice, neat progressions and advancements. Sometimes new discoveries dated to a certain period seem more
primitive than older finds.
Scientists have also found genes and specific proteins within genes in greater numbers in humans than chimpanzees that appear to be involved in cortex development and cognitive processes. Among
these are the DUF1220 protein and segments of genes that have undergone changes at a particularly rapid rate known as “human accelerated regions” or HARs. HAR1 is a gene associated with brain
development that is at least 310 million years old and is found in chickens as well as chimpanzees and humans. Before chimpanzees and humans split—for over 300 million years—only two of its 118
chemical “letters” changed. Since chimpanzees and humans split 5 to 6 million year ago 18 letters have changed—indicating that a high degree of change and evolution has occurred in hominids.
http://factsanddetails.com/world.php?itemid=1493&catid=56&subcatid=360#
GC-Biased Evolution Near Human Accelerated Regions
The Human Accelerated Regions (HARs) are strongly conserved elements, ranging in size from 100–400 bp, that show an unexpected number of human-specific changes. This pattern suggests that HARs
may be functional elements that have significantly changed during human evolution.
HAR Region Results Are Consistent with Simulations of GC-Biased Evolution
Human HAR1 and HAR2 both show evidence of specific function, the former by its highly specific expression pattern during neurodevelopment and the latter by its ability to enhance gene expression
during limb development.
Consistent with the idea that HAR regions may have experienced positive selection too long ago to be detected with population genetic methods, very few positively selected regions in the human
lineage have been identified to date, despite the existence of numerous public databases.
We find that the human substitution rate exceeds the expected neutral rate in all 49 HARs, while this is true for the chimp substitution rate in only 10 HARs.
http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1000960
Extra gene drove instant leap in human brain evolution
"There are approximately 30 genes that were selectively duplicated in humans," said Franck Polleux, an expert in brain development at The Scripps Research Institute. "These are some of our most
recent genomic innovations."
Interestingly, the novel gene appears to have arisen just as the fossil record shows a transition from human's extinct Australopithecus ancestors to the genus Homo (as in Homo sapiens), which led
to modern humans. That's also when the brains of our ancestors began to expand and when dramatic changes in cognitive abilities are likely to have emerged.
If this gene duplication did indeed produce an immediate effect during evolution as Eichler and Polleux suspect, they expect there must have been a fascinating period in human history characterized
by "huge variation" in human cognition and behavior. SRGAP2 and other human-specific gene duplicates might also help to explain the big differences between humans and other primates, despite few
apparent differences in our genome sequences.
Read more at: http://medicalxpress.com/news/2012-05-extra-gene-drove-instant-human.html
Creationism - Becuase it's easier to read one simple book than a whole bunch of hard ones.
The first article gives a brief synopsis of recent human lineage and a more detailed explanation how the pure chaos of interacting lineages makes the concept of a 'missing link' non-sensical.
The second two articles give a fascinating insight into forces other than 'natural selection' that have played a crucial role in the evolution of man's cognitive prowess and dextrous abilities.
HAR elements (Human Accelerated Regions) are highly conserved non-coding regions that underwent rapid evolution about 4 million years ago (the time equated with the emergence of homo-erectus).
The studies involved show how there was very limited adaptation of these elements before the split between humans and chimpanzees. The following period saw a period of rapid evolution, driven
by 'fertile' regions of DNA and a strong push toward G-C based preferential bonding. The hypothesis involves an 'emergence' time when preferential adaptivity would create immediate, disparate
differences in cognitive ability within hominid populations.
The final article deals with more recent human developments due to the partial duplication of a SRGAP2 gene involved in neuronal migration and plasticity.
It is believed that a recent relaxation in selective pressures allowed fixation of alleles to partially mimic the action of adaptive evolution.
EARLIEST MEN, HOMINIDS AND APES
There are two major groups, or genera of hominids: Australopithecus , which lived between 4 million and 1 million years ago and includes a number of species; and Homo , which appeared around
2.5 million years ago and includes, Homo habilis , Homo erectus and Homo sapiens (modern man).
Research by geneticist in the mid 2000s determined that the human genome and chimpanzees are only different by 1.23 percent. The one small percentage difference encompasses 35 million individual
chemical changes accumulated over the 5 million to 7 million years during which the species evolved apart. Put another way humans and chimpanzees share 98.77 percent of the same genetic material.
The study of early man has often been posed as a quest for “the missing link.” Most scientists bristle at the term. Tim White, a paleoanthropologist at the University of California, Berkeley,
told National Geographic, “The term is wrong in so many ways, it’s hard to know where to begin. Worst all is the implication that at some point there existed something halfway between chimp and
human. That’s a popular misconception that has plagued evolutionary science from the beginning.”
New discoveries have also debunked theories that human evolution was marked by a series of nice, neat progressions and advancements. Sometimes new discoveries dated to a certain period seem more
primitive than older finds.
Scientists have also found genes and specific proteins within genes in greater numbers in humans than chimpanzees that appear to be involved in cortex development and cognitive processes. Among
these are the DUF1220 protein and segments of genes that have undergone changes at a particularly rapid rate known as “human accelerated regions” or HARs. HAR1 is a gene associated with brain
development that is at least 310 million years old and is found in chickens as well as chimpanzees and humans. Before chimpanzees and humans split—for over 300 million years—only two of its 118
chemical “letters” changed. Since chimpanzees and humans split 5 to 6 million year ago 18 letters have changed—indicating that a high degree of change and evolution has occurred in hominids.
http://factsanddetails.com/world.php?itemid=1493&catid=56&subcatid=360#
GC-Biased Evolution Near Human Accelerated Regions
The Human Accelerated Regions (HARs) are strongly conserved elements, ranging in size from 100–400 bp, that show an unexpected number of human-specific changes. This pattern suggests that HARs
may be functional elements that have significantly changed during human evolution.
HAR Region Results Are Consistent with Simulations of GC-Biased Evolution
Human HAR1 and HAR2 both show evidence of specific function, the former by its highly specific expression pattern during neurodevelopment and the latter by its ability to enhance gene expression
during limb development.
Consistent with the idea that HAR regions may have experienced positive selection too long ago to be detected with population genetic methods, very few positively selected regions in the human
lineage have been identified to date, despite the existence of numerous public databases.
We find that the human substitution rate exceeds the expected neutral rate in all 49 HARs, while this is true for the chimp substitution rate in only 10 HARs.
http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1000960
Extra gene drove instant leap in human brain evolution
"There are approximately 30 genes that were selectively duplicated in humans," said Franck Polleux, an expert in brain development at The Scripps Research Institute. "These are some of our most
recent genomic innovations."
Interestingly, the novel gene appears to have arisen just as the fossil record shows a transition from human's extinct Australopithecus ancestors to the genus Homo (as in Homo sapiens), which led
to modern humans. That's also when the brains of our ancestors began to expand and when dramatic changes in cognitive abilities are likely to have emerged.
If this gene duplication did indeed produce an immediate effect during evolution as Eichler and Polleux suspect, they expect there must have been a fascinating period in human history characterized
by "huge variation" in human cognition and behavior. SRGAP2 and other human-specific gene duplicates might also help to explain the big differences between humans and other primates, despite few
apparent differences in our genome sequences.
Read more at: http://medicalxpress.com/news/2012-05-extra-gene-drove-instant-human.html
Creationism - Becuase it's easier to read one simple book than a whole bunch of hard ones.
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