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Author Topic:   Human Brain Evolution Was a 'Special Event'
melatonin
Member (Idle past 6209 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 43 of 65 (353341)
09-30-2006 8:25 PM


Thought this would be interesting in the context of this thread. Not sure how to upload pics, maybe someone else can.
Here's a link to Nick Matzke's recent summary of cranial capacity vrs time for hominins (australopithicus to homo sapiens).
Page not found · GitHub Pages
Edited by melatonin, : No reason given.

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 Message 44 by Taz, posted 09-30-2006 8:45 PM melatonin has replied

  
melatonin
Member (Idle past 6209 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 45 of 65 (353353)
09-30-2006 9:03 PM
Reply to: Message 44 by Taz
09-30-2006 8:45 PM


cheers gasby
If we look really closely at 6000-10,000 years ago, squint a bit, you can almost see where the soul was injected...
(j/k)

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 Message 44 by Taz, posted 09-30-2006 8:45 PM Taz has not replied

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melatonin
Member (Idle past 6209 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 48 of 65 (353533)
10-01-2006 9:19 PM


There are maybe half a dozen genes that are attracting special attention by Lahn's research group. Here's an abstract of a recent paper from his group.
Science 9 September 2005:
Vol. 309. no. 5741, pp. 1720 - 1722
DOI: 10.1126/science.1116815
Prev | Table of Contents | Next
Reports
Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens
Nitzan Mekel-Bobrov,1,2 Sandra L. Gilbert,1 Patrick D. Evans,1,2 Eric J. Vallender,1,2 Jeffrey R. Anderson,1 Richard R. Hudson,3 Sarah A. Tishkoff,4 Bruce T. Lahn1*
The gene ASPM (abnormal spindle-like microcephaly associated) is a specific regulator of brain size, and its evolution in the lineage leading to Homo sapiens was driven by strong positive selection. Here, we show that one genetic variant of ASPM in humans arose merely about 5800 years ago and has since swept to high frequency under strong positive selection. These findings, especially the remarkably young age of the positively selected variant, suggest that the human brain is still undergoing rapid adaptive evolution.
Just a moment...
This particular variant is not present in all humans but is the most recent development found. So, although it appeared around 6000 years ago, it doesn't really help a creationist viewpoint. Another more recent paper has questioned the notion the gene is undergoing positive selection (Currat et al., 2006). A mutation of ASPM causes microencephaly.
Employing the above strategy, we identified a number of candidate genes that might have played a role in human brain evolution. Examples include ASPM, Microcephalin, CDK5RAP2, CENPJ, Sonic Hedgehog, APAF1, and CASP3. A remarkable theme unifying all these genes is their involvement in determining neuronal cell number and brain size during embryonic development. When any one of these genes is mutated in either human or mouse, the result is a dramatically reduced brain size. For a subset of these genes, reduction in brain size appears to be the only discernible defect in the organism, indicating a highly specific function of the genes in regulating brain size. These findings led us to postulate that genes controlling brain size during development might have played a particularly important role in transforming brain size during evolution.
Bruce T. Lahn, PhD | HHMI
These are the others that are under examination. Not to say these are the only genes involved in the evolution of the human brain, of course.
The Lahn group are doing some very interesting stuff.
Edited by melatonin, : iffy html code

  
melatonin
Member (Idle past 6209 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 53 of 65 (362723)
11-08-2006 8:25 PM


Thought this would be of interest in this thread...
Evidence that the adaptive allele of the brain size gene microcephalin introgressed into Homo sapiens from an archaic Homo lineage
At the center of the debate on the emergence of modern humans and their spread throughout the globe is the question of whether archaic Homo lineages contributed to the modern human gene pool, and more importantly, whether such contributions impacted the evolutionary adaptation of our species. A major obstacle to answering this question is that low levels of admixture with archaic lineages are not expected to leave extensive traces in the modern human gene pool because of genetic drift. Loci that have undergone strong positive selection, however, offer a unique opportunity to identify low-level admixture with archaic lineages, provided that the introgressed archaic allele has risen to high frequency under positive selection. The gene microcephalin (MCPH1) regulates brain size during development and has experienced positive selection in the lineage leading to Homo sapiens. Within modern humans, a group of closely related haplotypes at this locus, known as haplogroup D, rose from a single copy 37,000 years ago and swept to exceptionally high frequency (70% worldwide today) because of positive selection. Here, we examine the origin of haplogroup D. By using the interhaplogroup divergence test, we show that haplogroup D likely originated from a lineage separated from modern humans 1.1 million years ago and introgressed into humans by 37,000 years ago. This finding supports the possibility of admixture between modern humans and archaic Homo populations (Neanderthals being one possibility). Furthermore, it buttresses the important notion that, through such adminture, our species has benefited evolutionarily by gaining new advantageous alleles. The interhaplogroup divergence test developed here may be broadly applicable to the detection of introgression at other loci in the human genome or in genomes of other species.
Freely available to download here...
http://www.pnas.org/cgi/content/abstract/0606966103v1
So maybe these particular genes were introduced from neanderthals or another archaic homo group. Quite interesting and I guess it was a 'special event' for the two individuals involved
Edited by melatonin, : added link

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 Message 54 by RAZD, posted 11-08-2006 9:46 PM melatonin has replied

  
melatonin
Member (Idle past 6209 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 55 of 65 (362755)
11-08-2006 10:14 PM
Reply to: Message 54 by RAZD
11-08-2006 9:46 PM


romantic collective unconscious
There does seem to be some sort of implicit bias towards neanderthals, could be some sort of latent remnant/collective unconscious of the 'special relationship', haha.
Guess these guys can help consolidate the neanderthal interbreeding hypothesis...
Ancient DNA pioneer Svante Pbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, says that this new work is "the most compelling case to date for a genetic contribution of Neandertals to modern humans." Indeed, Pbo says, he will now search for the haplogroup D variant of microcephalin in his own studies of the Neandertal genome.
http://sciencenow.sciencemag.org/...content/full/2006/1106/1

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