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#14806040
Hong Wu wrote:This is also why most politically ignorant liberal arts professors are socially liberal, they regularly try to seduce their students and this is facilitated by lecturing on the merits of group sex.

I knew there must be a reason people were liberal arts professors.
#14830191
As far as I know, medical practitioners may use family back-ground or membership of a genealogical sub-pop. demographic to evaluate a patient's condition and prognosis. If an individual patient's need for a script is indicated; it is provided on the basis of their specific condition, which includes heritable pre-conditions to certain diseases. For instance, not all people of the sub-Saharan/African genotype present with anemia, or, even carry the sickle-cell mutation. The fact of an heritable trait within a population merely proves, that the given group lived in comparative isolation and evolved to suit the survival landscape within their biota over a long enough period of time to adapt. It isn't, that the characteristics underlying the concept of race never existed, rather, the objection is to an over reliance on a variety of shoddy pseudo-scientific anthropological claims arising in the 18th cen. based on very little, or, corrupt data, concerning racial categorization of isolated populations, and their descendants. Race, as a concept, is an artifact of an earlier incomplete taxonomy of human variety.
Last edited by BrianHodge5000 on 05 Aug 2017 00:42, edited 1 time in total.
#14830208
I see this was resurrected so I will apologize if bringing up old arguments.
We know the basic 'races' interbred with different proto humans. The question is how certain are we that all these early humans had common ancestors? Does the DNA evidence prove this or only suggests it? It would seem logical our physical difference is due to this interbreeding.
#14830220
At the risk of repeating older arguments, I must point out, that variations in the genome also arise for reasons you've apparently failed to take into account, i.e. transcription errors due to faulty replication on a nucleic level, this leads to new phenotypes and the LONG slow process of testing the new mutation's fitness over many generations, and, whether the given new DNA 'code' adds some advantage to a species ability to raise more, and, better adapted progeny. So, it might seem to you logical, that any new variation in a population's characteristics has come about as a result of (in this example) an outside hominid population's DNA admixture. However, this assumption would be non-evolutionary and more akin to an animal-husbandry or cross-breeding paradigm for varietal morphology.
#14830223
BrianHodge5000 wrote:At the risk of repeating older arguments, I must point out, that variations in the genome also arise for reasons you've apparently failed to take into account, i.e. transcription errors due to faulty replication on a nucleic level, this leads to new phenotypes and the LONG slow process of testing the new mutation's fitness over many generations, and, whether the given new DNA 'code' adds some advantage to a species ability to raise more, and, better adapted progeny. So, it might seem to you logical, that any new variation in a population's characteristics has come about as a result of (in this example) an outside hominid population's DNA admixture. However, this assumption would be non-evolutionary and more akin to an animal-husbandry or cross-breeding paradigm for varietal morphology.


Well, I did not understand your specialized vocabulary, but I don't see how you answered my questions. How do you figure two different proto humans mating is non evolutionary since it apparently affected our evolution?
Does DNA prove proto humans had common ancestry? As far as I know this is just theory and therefore we could have different 'racial ' characteristics.

Edit: How do we classify the guy in China with 44 chromosomes? His offspring will also need a category. Do we call them a different species or do we admit they are a distinct race? :?:
#14830237
I don't figure that. Your earlier comment suggested earlier established races, "We know the basic 'races' interbred with different proto humans." Here's the story so far: science has determined, to the best of it's ability, that there was a common ancestral population, or an earliest gene map for the earliest human population. It developed in a certain habitat, and of course, was isolated from other hominids, which were not of the same species, such as Neanderthal for example. If, you're saying that there were other species of hominid around concurrent to homo sapiens you'd be correct. But, you wouldn't call them 'races', as they were other species, not merely varieties or subspecies. The question of how sure paleo-anthropology is about a common ancestral population, as progenitor for present day homo sapiens is based on any new DNA data that comes to light and the ability to date it accurately. OK? Now, I was talking about the historical categories within the homo sapiens species, and how the concept of 'race' has become synonymous with "species", due to the exaggeration of superficial, and not altogether meaningful differences. What was a difference in degree, we called 'race', as if, to indicate a difference in kind on a par with species. Natural species get reclassified by biologists on a regular basis, as new data appear. Sometimes planets are reclassified, or whole "genera" are collapsed inside new "orders", as discoveries are made. As I said in an earlier post, the facts, that supported the concept of the term 'race", in an earlier age have been superseded and recontextualized by advanced DNA evidence, and, this issue is solely a question of taxonomy.
#14830465
ThirdTerm wrote:Image

Image

The two PCA plots basically show that all non-Africans cluster continuously with each other. It's natural that those groups which exchanged genes historically by living side by side plot closely in PCA maps such as the Japanese and the Chinese, or the Russians and Ukrainians. PCA plots naturally demonstrate a close correspondence between genetic and geographic distances and as geographic distance increases, genetic distance increases in a linear manner. The larger the sample size, the more continuous a PCA plot becomes for non-Africans, which some earlier studies such as Tang et al. (2005) failed to do with 20 or less samples. Africans are the outlier of any of these geographic groups due to the lack of Neanderthal genes, except for North Africans who are plotted in the European range along with the Arab populations below.

Image



I'm still not convinced with the sapien/Neanderthal admixture idea. The demonstrated frequency relationships could alternately be explained by found affects. The Euroasian group represents the expansion of the population frequencies of the North African group. Thus the sub Saharan group would be expected to show greater variation relative to all other groups and this would show up in studies as the sub Saharan group being the outlier.

Furthermore, if it could be shown that sapien/Neanderthal admixture occurred, this would indicate those two groups weren't quite separate species. The biological species concept is founded on the notion of reproductive isolation. True some species can produce infertile hybrids, such as horse/ donkey hybrids (mules). But if Neanderthal contributed to euroasian gene pools then the hybrid was fertile, thus the two parent groups were not seperate species. Either that or the biological species concept must be replaced with another concept. Paleospecies do make species theorising difficult.
#14830467

Image
Figure 1

Before their disappearance from the fossil record approximately 40,000 years ago, Neanderthals, the ancient hominin lineage most closely related to modern humans, interbred with ancestors of present-day humans. The legacy of this gene flow persists through Neanderthal-derived variants that survive in modern human DNA; however, the neural implications of this inheritance are uncertain. Here, using MRI in a large cohort of healthy individuals of European-descent, we show that the amount of Neanderthal-originating polymorphism carried in living humans is related to cranial and brain morphology. First, as a validation of our approach, we demonstrate that a greater load of Neanderthal-derived genetic variants (higher “NeanderScore”) is associated with skull shapes resembling those of known Neanderthal cranial remains, particularly in occipital and parietal bones. Next, we demonstrate convergent NeanderScore-related findings in the brain (measured by gray- and white-matter volume, sulcal depth, and gyrification index) that localize to the visual cortex and intraparietal sulcus. This work provides insights into ancestral human neurobiology and suggests that Neanderthal-derived genetic variation is neurologically functional in the contemporary population.

The analyses reported here were restricted to a sample of individuals of European descent. It is known that the degree of admixture is variable in different modern populations. For example, East Asian populations have been found to have a larger portion of the genome derived from Neanderthals than European populations (up to 20% more), though the admixed regions of the genome are not necessarily overlapping5. This raises the possibility that the findings reported here may not translate to other populations, where Neanderthal introgression may involve other genomic regions that may be functional in different ways. As large neuroimaging and genetic data from different populations become available, future work could investigate this possibility by performing similar analyses in different populations, including using African populations with minimal Neanderthal admixture as potential “null hypothesis” groups.

Finally, our analyses of the relationship of our findings to specific Neanderthal-derived gene variants, revealed a single 53 kb LD block that was significantly associated with the shared variance of the identified Neanderthal-derived brain and skull changes and that encodes for the gene GPR26. In line with our primary hypothesis for this analysis, that such genetic influences would be found in genes preferentially expressed in the human brain, GPR26 in fact encodes a G-protein coupled receptor subtype that is preferentially expressed in the brain29. Interestingly, in human post-mortem brains samples, expression of GPR26 peaks perinatally39, when the visual system is first challenged, indicating that it may play a role in development of the human visual system. Mouse models also show this gene to impact both affective and energy homeostatic functions40, 41. Additionally, this G-protein-coupled receptor has been shown to form oligomers with the 5-HT1a receptor42, perhaps providing a putative mechanism underlying the Neanderthal-related brain changes found here. Although the nature of the influence of this region on modern and archaic human nervous systems is uncertain, a possible link between brain energy regulation, neurodevelopment and mature structure may merit further investigation.

Because the NeanderScore measure employed here is, itself, polygenic, it is likely that the genetic contributions to skull and brain morphology we observed involve a number of different genetic loci. Nonetheless, our exploratory post-hoc genome-wide analysis of the shared variance of these findings identified only a single significant region. It is unlikely that this single locus, the LD block on chromosome 10, fully explains the brain and skull findings, and in fact, the Manhattan plot in Fig. 4 suggests that multiple other regions that do not meet strict Bonferroni corrections may represent some degree of true signal. Our modest sample size may have been underpowered to identify these additional signals. As larger datasets containing both genotype and neuroimaging data of brain and skull become available, future work will likely uncover additional genetic regions contributing to these findings.

Taken together, the associations between Neanderthal sequence variation and co-localized skull and brain morphology in modern humans engender an enduring, living footprint of H. neanderthalensis – a residual echo of shared, intimate history with a fallen lineage close to our own. To the extent that characterization of Neanderthal variation in present-day people can provide insights into archaic human phenotypes, this work can form the basis of future studies aimed at a more thorough understanding of Neanderthal biology. By the same token, we suggest that Neanderthal gene flow into modern humans is not only of evolutionary interest, but may also be functional in the living H. sapiens brain, revealing novel genetic influences on neurodevelopment of the visuospatial system upon which a fuller account of molecular mechanisms of IPS-driven normative mental functions, such as visuospatial integration and tool manipulation, can be built. This, in turn, may inform models of IPS-associated cognitive disability as seen in select developmental and neurological disorders43,44,45,46.

https://www.nature.com/articles/s41598-017-06587-0


This new Nature study by Gregory et al. (2017) further confirmed Neanderthal introgression into the human genome. Using MRI, the authors showed that the amount of Neanderthal-originating polymorphism carried in living humans is related to cranial and brain morphology. East Asian populations have up to 20% more of their genome derived from Neanderthals.
#14830469
One thing that fascinates me is some estimates place the beginning of sedentary agriculture at the same time period the last of the proto humans disappeared. This causes me to speculate there must have been widespread conflict among the groups. War is a means of transferring DNA to otherwise incompatible groups, while remaining apart. So perhaps a combination of interbreeding and isolation? Curious if someone in the field has considered this? Obviously this is not my field. :D
#14830508
One thing that fascinates me is some estimates place the beginning of sedentary agriculture at the same time period the last of the proto humans disappeared. This causes me to speculate there must have been widespread conflict among the groups. War is a means of transferring DNA to otherwise incompatible groups, while remaining apart. So perhaps a combination of interbreeding and isolation? Curious if someone in the field has considered this? Obviously this is not my field. :D


Do a Google search on "Dunbar's Number". Fascinating.
#14830511
Drlee wrote:Do a Google search on "Dunbar's Number". Fascinating.


Thanks. I remember reading about it before, but had forgotten. It is fascinating and allows you a visualization when discussing primitive groups.
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