How has DNA and genetic markers revolutionized our views of human origins?

Question

How has DNA and genetic markers revolutionized our views of human origins?

Answer 1

How about the realization that humans share 97% of their DNA with primates.  So, only 3% is us.  How about that we can now do genetic testing to determine many serious disorders like Huntington's. And, finally, for a simple little recognized genetic marker: I have dimples, look higher, on my shoulders, and so did my father. Also how we clasp our hands together is genetic. (right finger up or left finger up) I could go on and on.

Answer 2

There was a question in another series about what happened to the Cro-Magnons.  According to National Geographic, any male having a Y-chromosome marker in the haplogroup R1 is descended from a father-father-father... etc genealogy originating from the Cro-Magnons in Europe.  

My origins are Antioquia, Colombia.  My Y-chromosome came from Spain (R1b) and is shared with many of the men in Western Atlantic Europe, including the British Isles, where our western Europe Cro-Magnons from France and Spain spread as the Ice Age receded.  There was another cousin R1a that split off further eastward in Europe as the R1 was heading west.

When the R1 arose from the R, just east of the Caspian Sea, about 35,000 years ago, in the approximate zone now known as Kazakhstan, the same forerunner of the R called P also had a descendant Q who went the other way and populated Siberia, then crossing over to Alaska and becoming one of the founders of the American Indian lineages.

As I read it, the so-called Indo-Europeans really came much, much later and could explain why the Basque area speaks an unrelated non-IE language.  The most frequent Viking haplotype "I" was from a different root coming upwards through Europe directly from the Middle East, not the R1 which took a longer Central Asian route much before.  There were other haplotypes branching out into Europe, and collectively they are now the "Europeans".  You can see this in the National Geographic website.  I have ancestors with most of them.  Even though my own Y-Chromosome is R1b, I have origins mostly in Spain and Portugal but also Italy, Norway, Scotland, Flanders, Berber, also Greek and Turkish.  I have some Native American, some of which is DNA most likely due to being Colombian, but some of the proto-Native American DNA is also inherited from the European lineages themselves - surprise...

If you look at that or similar websites including Wikipedia, the R1 and the Q were both descendants of the P lineage around present-day Kazakhstan.  R1 went west, the Q went east.  It could have been different, and a brief choice in hunting direction defined if your descendants would become European or American Indian over the next millenia.

Looking at many bits of info especially in a website in Ancestry by DNA, it's very unlikely that anyone in the world is 100% purely this or that.  Everyone is made of DNA material found in the four main continentals, and the majority of your DNA MAY confirm your appearance as one of them.  The average "European" American in the USA, from a sample of 207, is actually 90.5% European, 3% Sub-Saharan African, 2.8% East Asian and 3.8% Native American.   Yes, the rounded numbers add up to 100.1%, but that's how it was tabulated on Ancestry by DNA's website.  In Europe itself, none of the samples are 100% European.  No point arguing with me on this - if you don't believe it then order the DNA 2.5 test!  Or also the DNATribes test is very interesting because it locates specific populations for you on a map.  DNA 2.5 only gives you a general percentage breakdown, but they complement each other when forming the big picture.  DNAConsultants can do the maternal and/or paternal haplotypes or any of these.

Answer 3

DNA allows us to track migrations based on haplogroups (basic genetic groupings of people) as well as tracking time via mutations that tend to happen at specific rates in some genes.  Besides morphology we can recover DNA in more & more ancient Homo genes... Neandertal comes to mind.  The current complete sequencing (1st draft) of the neandertal genome is slated for late 2008 or early 2009.

While DNA has provided many answers, it has raised many more questions. Mungo man of Australia, ~ 40,000 yrs BCE, appears to be a modern sapien, but his MtDNA tests as closer to Neandertal than to sapien... casting doubt on the mitochondrial Eve hypothesis & the time the 1st sapien left Africa.

http://www.abc.net.au/science/slab/mungo...

The "Out of Africa" hypothesis is no longer as solid as it was 10 yrs ago but the "MultiRegional" hypothesis has been shaken too.  Several introgressed or very recently mutated genes have been discovered among the non African populations of the World & many suspect they are from a more ancient line of Homo (either neandertal or erectus.)

See human gene introgression or MCPH1 in Chromosome 8.

In addition DNA has redrawn the migration map to the Americas since the discovery of Haplogroup B & Haplogroup X in the Amerinds (Haplogroup X being found in Western Europe & not in Asia & Haplogroup B being a Pacific Islander Haplogroup.)

New hypothesis on the appearance of haplogroup X in the Americas suggests they followed the Atlantic ice pack to North America, hunting marine animals.  Some evidence exists to incicate the Clovis culture & tool making origionated in Spain & was brought to the Americas ~20,000 yrs ago by the Solutrean culture from Spain or Southern France. Look about 1/2 way down on this link.

http://www.familytreedna.com/public/x/

Answer 4

It just took the arguing to new levels. The media and some researchers claim we are all descended only from a group of Africans that left home 70k years ago, but the fossil record shows modern humans in China at Luijang over 100k ago.

The fossil record also supports interbreeding with other Homo types, as does a fair bit of DNA research that you don't get to hear about on the news.

http://www.pnas.org/cgi/content/abstract...

X chromosome evidence for ancient human histories

Eugene E. Harris and Jody Hey*

Diverse African and non-African samples of the X-linked PDHA1 (pyruvate dehydrogenase E1 subunit) locus revealed a fixed DNA sequence difference between the two sample groups. The age of onset of population subdivision appears to be about 200 thousand years ago. This predates the earliest modern human fossils, suggesting the transformation to modern humans occurred in a subdivided population. The base of the PDHA1 gene tree is relatively ancient, with an estimated age of 1.86 million years, a late Pliocene time associated with early species of Homo. PDHA1 revealed very low variation among non-Africans, but in other respects the data are consistent with reports from other X-linked and autosomal haplotype data sets. Like these other genes, but in conflict with microsatellite and mitochondrial data, PDHA1 does not show evidence of human population expansion.

http://mbe.oxfordjournals.org/cgi/conten...

Abstract

The human RRM2P4 pseudogene has a pattern of nucleotide polymorphism that is unlike any

locus published to date. A gene tree constructed from a 2.4 kb fragment of the RRM2P4 locus

sequenced in a sample of 41 worldwide humans clearly roots in East Asia and has a most recent

common ancestor ~2 million years before the present. The presence of this basal lineage

exclusively in Asia results in higher nucleotide diversity among non-Africans than Africans. A

global survey of a single nucleotide polymorphism that is diagnostic for the basal, Asian lineage

in 570 individuals shows that it occurs at frequencies up to 53% in south China, while only one

of 177 surveyed Africans carries this archaic lineage. We suggest that this ancient lineage is a remnant of introgressive hybridization between expanding anatomically modern humans emerging from Africa and archaic populations in Eurasia.

http://accuca.conectia.es/archaic_genes_...

http://www.genetics.org/cgi/content/abst...

Fossil evidence links human ancestry with populations that evolved modern gracile morphology in Africa 130,000 - 160,000 years ago. Yet fossils alone do not provide clear answers to the question of whether the ancestors of all modern Homo sapiens comprised a single African population or an amalgamation of distinct archaic populations. DNA sequence data have consistently supported a single origin model in which anatomically modern Africans expanded and completely replaced all other archaic hominin populations. Aided by a novel experimental design, we present the first genetic evidence that statistically rejects the null hypothesis that our species descends from a single, historically panmictic population. In a global sample of 42 X chromosomes, two African individuals carry a lineage of non-coding 17.5 kilobase sequence that has survived for over one million years without any clear traces of ongoing recombination with other lineages at this locus. These patterns of deep haplotype divergence and long-range linkage disequilibrium are best explained by a prolonged period of ancestral population subdivision followed by relatively recent interbreeding. This inference supports human evolution models that incorporate admixture between divergent African branches of the genus Homo.