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Do we have the same DNA as 12-20.000 years ago?

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  1. Sep 16, 2014 #1
    As the title says. I found some contradictory articles about us (not) having the same dna as prehistoric men 50.000 years ago.

    So how did our dna evolve in the last tens of thousands of years especially human dna of today compared to human dna at the end of pleistocene and can i find some studies?
     
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  3. Sep 17, 2014 #2

    Simon Bridge

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    Depends how you are measuring the differences. When you can define your terms you'll be able to make some headway.

    It is unlikely that you personally have the same DNA as any mesolithic man.
    OTOH: we cannot get samples of DNA that old to check.

    Note: evolution is an ongoing process - humans have evolved over the last 20000years the same way they evolved over the millions of years before that.
    But you don't mean "mechanism" do you, you want to know about the specific alleles have been added or removed in the last 20000 years right?
     
  4. Sep 17, 2014 #3
    Changes in the genome of humans and all animals in general is a steady, constant process, whose current form is determined largely by natural selection in any given animal. So the answer to your question is no. Although many of the gene sequences remain conserved, there is always some adaptation going on somewhere.

    One example are the microcephaly related genes in primates, which have recently been linked to brain development in hominins. In fact, there is evidence that at least one variant of one of these genes, ASPM, has become incorporated into the human genome within the last 6000 years:http://www.ncbi.nlm.nih.gov/pubmed/16151010


    Typically by polymorphisms in the gene sequences. One popular test for the adaptive evolution of a gene is the McDonald–Kreitman test, which measures the ratio of non-synonymous to synonymous substitutions in a given gene. Over a certain ratio, it is thought the gene is undergoing positive selection.http://hmg.oxfordjournals.org/content/13/5/489.long

    See also:
    http://hmg.oxfordjournals.org/content/13/11/1139.long
    http://en.wikipedia.org/wiki/Single-nucleotide_polymorphism
    http://www.ncbi.nlm.nih.gov/pubmed/24898820
     
    Last edited: Sep 17, 2014
  5. Sep 17, 2014 #4

    D H

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    You have three dates, 50,000, 20,000, and 12,000 years ago. Which is it?

    Humans are still evolving. We transitioned from hunter-gatherers to agriculture about 12,000 to 11,000 years ago. Our teeth are about 10% smaller than those of our hunter-gatherer ancestors, and we produce a lot more salivary amylase (an enzyme in our saliva that aids the digestion of starches as soon as we start chewing) than did our hunter-gatherer ancestors. Many of us can digest milk as adults. Our ancestors couldn't. At least five mutations have occurred in Africa, Europe, and Asia that let us continue to drink milk after infancy and into adulthood. All of these are occurred within the last 10,000 years or so.

    A side effect of this transition from hunter-gatherers to agriculture was a marked increase in malaria, both in terms of number of cases and lethality. Our ancestors moved to wetter areas where agriculture is easier and settled down. This gave mosquitos a nice environment in which to breed and mature and a nice sedentary source of blood for female mosquitos during the few week or so they spend in their adult form. This in turn provided an increased avenue for the diseases transmitted by mosquitos. The population of the deadliest form of the malaria parasite, Plasmodium falciparum, skyrocketed with the advent of agriculture. We in turn evolved multiple defenses. Hemoglobin S (sickle cell) in sub-Saharan Africans, hemoglobin-C in western Africans, thalassemia in Mediterranean regions, and hemoglobin-E in southeast Asians are all evolutionary defenses against malaria, and they are all rather recent developments.

    This transition to agriculture coincided with the end of the last glaciation. This opened up new territories for humans. There was a problem, though: The dark colored skin that evolved when our ancestors live in equatorial regions became a maladaptation in the far north. Exposure to ultraviolet light damages skin and can lead to skin cancer, but it also is responsible for producing vitamin D. Various mutations that led to lighter skin color began cropping up in western Europe and eastern Asia. The Blond hair and blue eyes seen in northern Europeans is a rather recent adaptation. Green eyes are an even more recent change.

    The end of the glaciation also opened up high altitude locales, most notably the Tibetan and Andean plateaus. The DNA of the peoples who live there has changed to enable them to better process the reduced oxygen content in those high altitude regions.
     
  6. Sep 17, 2014 #5
    Ok, but it is often said that humans and chimps have like 99% the same DNA. So how much of a difference could it be ? I guess that it would be less than 1% maybe 0.01 % ?

    If an infant from that era, the end of pleistocene, would magically be born and raised today in a normal family environment, would he be pretty much like all the rest of us in terms of behaviour (social/sexual) ?
     
    Last edited: Sep 17, 2014
  7. Sep 17, 2014 #6

    Ygggdrasil

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    Scientists have characterized a number of genetic changes that have evolved fairly recently in human populations. Here's a somewhat old, but good NY Times article describing a few: http://www.nytimes.com/2010/07/20/science/20adapt.html?emc=eta1&_r=0

    If you're interested in delving more deeply into the subject, here's a paper from last year describing a data-mining approach to look at human genome sequences from around the world to identify regions that may reflect recent adaptations: Grossman et al. 2013. Identifying Recent Adaptations in Large-Scale Genomic Data. Cell 152: 703. http://dx.doi.org/10.1016/j.cell.2013.01.035 [Broken].
     
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  8. Oct 13, 2014 #7
    Don't look at the DNA differences between humans and other animals in too linear a fashion. This creates a lot of misconceptions, especially in the popular media. DNA is not a blueprint for how a final organism will turn out in the same way architectural blueprints may be for a high rise or a printed circuit board/microprocessor. DNA interacts with the environment through development to create the final organism in a complicated fashion. This is the science of "evo-devo". One example are a small set of regulatory genes that control the symmetric/asymmetric division of neuroepithelial cells that build the neocortex. One model is that there is a mutation in one or a few of these genes that delays the splitting of these cells for a few generations, which leads to the enormous increase of the size of the cortex in primates/humans. Thus, a change in the behavior of one or a few genes can have a very large effect on the final structure of the organism in general. When you have many thousands of genes of in the genome, talking about a high degree of compatibility in those genomes only you tells you so much.

    http://www.ncbi.nlm.nih.gov/pubmed/7482803
     
  9. Oct 13, 2014 #8

    Pythagorean

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    I believe the 99% figure excluded "junk DNA", which includes gene expression controls. With the same set of genes and a different expression routine, you can come up with some very different morphological and chemical system designs.
     
  10. Oct 14, 2014 #9
    There are several different senses of "same DNA" and this confuses several of them.

    - 1. Exactly the same genome? No, we have evidence of new traits (height and lactose tolerance), as well as many ongoing gene sweeps that may or may not fixate (give stable traits) but meanwhile means trait frequency changes.

    - 2. Roughly the same traits (due to roughly the same genome)? Probably so, it seems the basic toolkits of tools, art, language and social behavior (including sexual) was present in anatomically modern man when it emerged out of Africa. The question would be if such an individual would be within or close to the existing variation, and I would think so.

    But this is another question entirely. Looking at human trait changes can be done by looking over subpopulations (sweeps). Comparison with other hominins may not be so informative.

    What I understand they have still to grok the differences in evolutionary speed (genome changes) between hominins and over time. We have had very complicated and different evolutionary trajectories. Chimps has evolved faster over longer time than we have (recent change), because they have been more successful for most of it. About 10 000 - 100 000 effective breeders (IIRC) vs about 1 000 - 10 000 for humans:

    "... mutation would take a long time to build variation back up after it is lost long term effective population is very sensitive to a bottleneck event. This is why despite our census size of 7 billion long term effective population for humans is closer to the range of 1,000 to 10,000. We went through bottlenecks in our relatively recent past."

    [ http://www.unz.com/gnxp/elon-musk-is-wrong-about-genetic-diversity/ ]

    And especially in monkeys, microRNA seems to be the main evolutionary driver. MicroRNA regulates gene expression, and this is then the main evolutionary difference between hominins. I doubt they are well researched.

    Finally, there is no simple map between alleles and traits. Peruvians have one allele change for height tolerance IIRC, it was a late evolution (within the last 15 kyrs or so). Tibetans have 5 IIRC, and they got it from Denisovans, a smaller human population (so more random change) that had lived in the area for perhaps 50 kyrs or more. And if we go to height differences there are thousand of genes involved...
     
    Last edited: Oct 14, 2014
  11. Oct 15, 2014 #10
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  12. Oct 15, 2014 #11

    Pythagorean

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    The nature article is referring to mitochondrial DNA
     
  13. Oct 15, 2014 #12

    Simon Bridge

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    Probably a valid point both ways - we would not normally compare mitochondrial dna to check, say, a familial relationship. OTOH: the field is moving somewhat quickly; maybe I should be more careful when I'm being fascetious - amend statement to "dna useful for such a comparison" or whatever makes best sense to you.

    Checking:


    I cannot tell from the various "complete genome" claims in nature - but it looks like the consensus from these is that even the mitocondrial dna was quite different in ancient times. It would be fair to say that homo-heidelbergensis' genome would be strikingly different from the thread starters - though I don't have access to a sample of that either.

    i.e. denisovan genome sequence... I think counts as the oldest currently.
    http://www.sciencemag.org/content/338/6104/222

    But shouldn't we be interested in homo sapiens?
    http://www.nature.com/search/execut...start=1&sp-c=25&sp-m=0&sp-s=&siteCode=default
    ... starting point. Some free papers in there: enjoy.
     
  14. Oct 23, 2014 #13

    Ygggdrasil

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    Nature just published a paper detailing the full genome sequence of a 45,000-year-old modern human. This should probably shed some light on the OP's question:
    Fu et al. 2014. Genome sequence of a 45,000-year-old modern human from western Siberia. Nature: 514, 445. http://dx.doi.org/10.1038/nature13810 [Broken].

    The genome sequence is available here: http://www.ebi.ac.uk/ena/data/view/PRJEB6622
     
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  15. Oct 31, 2014 #14
    Is it really that "constant", however? If so, how would things such Cambrian explosion occur?
     
  16. Nov 1, 2014 #15
    Well, the Cambrian explosion is certainly an anomaly that needs special investigation. There can be these sort of bifurcative events from time to time. One example is the demise of the dinosaurs 65 mya, which reorganized the dynamics of the ecosphere to allow eutherian mammals to grow in mass/size and flourish, whereas previously they survived better by staying small and out of the way. The cause of the Cambrian event, though, is much more deep and enigmatic than the Cretaceous–Paleogene extinction event.

    As far as my comment about "Changes in the genome of humans and all animals in general is a steady, constant process, whose current form is determined largely by natural selection in any given animal," that is true, the chemical genome of every organism is always undergoing a steady, constant mututive pressure from environmental insults. This pressure, though, is heterogeneous in different individuals, and the deleterious mutations vanish over one or a few generations typically, which maintains a relatively conserved genome in the long run. It's only those mutations that increase fitness that alter or "evolve" the genome.
     
  17. Nov 1, 2014 #16

    Ygggdrasil

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    Whether evolution proceeds by creeps or jerks (i.e. whether evolution occurs slowly and gradually or whether it comes about in periods of rapid change followed by periods of relative stability) is still an http://evolution.berkeley.edu/evosite/evo101/VIIA1aHypotheses.shtml [Broken] debated by evolutionary biologists. Of course, these models are not necessarily mutually exclusive, and which mechanism dominates may depend on how rapidly the environment is changing.
     
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  18. Nov 1, 2014 #17

    Pythagorean

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    Robert Sopolsky tells an interesting story about this in his open human behavioral biology lectures, According to him, the jerk theory was proposed by antrhopologists (who are digging up bones from distinct points in time and often not seeing the morphologies that existed in the time-span between dig sites).

    Perhaps morphology is a place where jerks can happen though, since they are more emergent phenomena, while purely molecular processes (expression, signaling, immune system, etc) undergo more gradual changes that aren't as observable (until they lead to a morphological change).
     
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  19. Nov 3, 2014 #18
    But arguably perhaps not an anomaly re diversity. The Ediacaran assemblies looks similar in evolution rate of diversity IIRC.

    The rest, why there was a lag between eukaryotes (mitochondrion event 2-1 Ga bp) billion years before present) and the Ediacaran (where body plans evolved in animals, which diversification took off in Cambrian) has been predicted out of many factors such as rare soft body fossilization.

    Just this week a first comprehensive chromium analysis of near surface ocean sediments show low oxygen levels, < 0.1 %, during 1.8 - 0.8 Ga bp. That would have delayed complex eukaryote multicellularity in everything from plants (who also breath) to animals. 0.8 Ga bp coincides rather well with attempts to use molecular (genome) clocks to look for the first Metazoan splits. [ http://onlinelibrary.wiley.com/doi/10.1002/gj.1074/abstract ]
     
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