How did the different human races evolve?

Discussion in 'Science & Society' started by Balder1, Jan 26, 2003.

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  1. Mojado? keeep your racist stuff to yourself & your friends. Everybody that came from somewhere else, had to get wet to get here

    you as a Peruvian, should have known better, now lets get back to the topic
     
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  3. Fraggle Rocker Staff Member

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    Actually, for many years that was the definition of a genus. Given free choice the various species would not choose to mate outside their species. But when constrained they could interbreed. Fertility of the offspring was not an issue.

    Equus (horse x donkey) produce infertile offspring, mules. But canis (wolf x coyote), felis (cat x ocelot), cattle (bison x domestic) all produce fertile hybrids. As do a huge number of birds. It's easy to get birds to crossbreed in captivity, and macaws, cockatoos, conures, and Amazons all interbreed freely, each within their own genus, and have given rise to a rainbow of second- and third-generation hybrids.

    Zoologists have gone crazy reclassifying genera since the advent of DNA analysis. They've created new genera and have now faced us with the perplexing problem that two species who are not even of the same genus can crossbreed. Cats and ocelots are supposedly now in seperate genera but that hasn't stopped every large pet shop from having ocicats for sale (which are quite fertile and into multi-generation hybridization). Ditto for the hyacinth macaw and the blue-and-gold macaw. Now in different genera, just as Mr. Colson finally got them to crossbreed and got the hybrid named after himself. Too early to tell whether they are fertile, but preliminary efforts were not promising.

    Anyway, different subspecies will absolutely have fertile offspring. By definition they have the same number of chromosomes.
     
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  5. Hideki Matsumoto ñ{ìñÇÃóùâ?ÇÕêSÇÃíÜÇ©ÇÁóàÇ ÈÅB Registered Senior Member

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    Coloured people are more resistant to UVA radiation burns than "whites". This is due to the colourant Melanin present in the skin.
     
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  7. you just went back & forth on the same issue, you must really be John Kerry?
    Study the following:
    http://dictionary.reference.com/search?q=genus
    http://dictionary.reference.com/search?q=species&r=67
    http://www.sciencedaily.com/releases/2004/01/040127085316.htm
    http://www.sciencedaily.com/releases/2003/09/030923065212.htm
    I've read more scenarios; that we ate them, out-hunted them, inter-breeded, out-bred them, or that their cold-temp adaptations led to extinction after the ice age ended

    Question:
    your answer:
    and the answer is:
    about 100,000, give or take a few k's

    http://www.mnh.si.edu/anthro/humanorigins/ha/sap.htm
     
  8. Athelwulf Rest in peace Kurt... Registered Senior Member

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    Care to tell me how I went back and forth on the same issue? I'm confident that that post was to the point. I'm also confident that I composed that post using the best of my knowlegde.
     
  9. check this out:
    http://www.mnh.si.edu/anthro/humanorigins/faq/race.htm
    from:
    http://www.mnh.si.edu/anthro/humanorigins/faq/dna.htm
    interesting points in red bold lettering
     
  10. re-read it yourself

    also, your answer:
    is off by about 90,000 years
     
  11. Athelwulf Rest in peace Kurt... Registered Senior Member

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    5,060
    Ahem, Randolfo.

    That doesn't help me. I still stand by my last statement. Prove to me that I'm going back and forth on the same issue.
     
  12. Alsophia Theophilos Registered Senior Member

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    Randolfo
    Is the 550,000 years a typo? "divergence between modern human mtDNA and Neanderthal mtDNA prior to 550,000 years ago"
     
  13. Erring Flatley Erring Flatley Registered Senior Member

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    95
    To get away from the social side of this here is a real life example of color evolution. In Honolulu thirty years ago all the city's pidgeons were the ordinary dark color except for a few that someone let go at a large banyon tree in the Waikiki area. After ten years the gene for white had spread throughout the pidgeon population in Waikiki, but almost all the others in the city were still dark. After ten more years most of the pidgeons in all of Honolulu were white. And after ten more years the gene for white was spread over the entire island. The population of the island changed from a mostly dark color to a mostly white color in thirty years. It simply happened that white birds stood the bright sunlight better, gathered more food, laid more eggs,and slowly the gene for white spread through the population. During all that time the birds freely interbred without regard for color. It was simply the gene that spread through the population, not one group overtaking the other.
     
  14. pbxoso Registered Member

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    1
    The latest Discover magazine has an excellent cover story on human genetics and race. The article points out that science hasn't answered the question of why so much varience exists between the races, especially given the fact that our genes are so similar. I remember from my biology class that the northern Chinese are as pale as the palest of caucasians and that was attributed to climate. Seems when they moved north they no longer needed darker skin to protect from sunlight.
     
  15. alibim Registered Member

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    19
    Towards the end of WWII Holland (the Netherlands) was treated pretty much like a country-sized concentration camp by the Nazis ie starvation diets all round. Any children resulting from pregnancies during that time were pretty stunted individuals. Yet their own children & grandchildren, born to people with much better diets & healthcare, were back to normal height & size. In other words, it's the nature/nurture thing: environmental conditions have a significant effect on the manner in which genes are expressed. You may have the genetic potential to be 6ft 3ins but if you don't get the optimum diet, you probably won't achieve it. But the genes are still there to be passed on to your offspring.
     
  16. wesmorris Nerd Overlord - we(s):1 of N Valued Senior Member

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    Hmm..

    It makes me wonder if evolution, or more specifically, mutation, it driven by the damage it takes in current form. If for instance, a serious vitamin D deficiency is incurred in a group for a long period of time, perhaps that very deficiency can damage their DNA in a way that when it is propogated, compensatory features emerge (e.g. darker skin or whatever). Perhaps that's part of how evolution is "driven"?

    Just a passing thought.
     
  17. CharonZ Registered Senior Member

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    786
    No it won't. A similar stance was taken by Lamarck (though at that time DNA was unknown), however there is not a single instance known that a factor specifically changes DNA (inerhitably) that way.
    The body might react to deficiency by differential expression of specific genes, but these have to be there already in the first place.
     
  18. Ophiolite Valued Senior Member

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    9,232
    The posts from CharonZ and alibim have reminded me of a clear piece of evidence for Lamarkian evolution! The Dutch are now the tallest people in Europe. Why? Very simple. This is a pre-adaptation to the flooding of the Netherlands that will occur as a result of rising sea levels: they can walk along the polders with their heads just above water. So,from a single data point we have incontrovertible proof of three contentious theories: Lamarkian evolution, precognition and global warming. That's value for money research!
     
  19. wesmorris Nerd Overlord - we(s):1 of N Valued Senior Member

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    That's somewhat misleading given that DNA consists largely of "junk" as we know it.
     
  20. sorry, for not answering sooner, I did not receive any notices that someone had responded, so I didn't re-check this thread.

    No, it's not a typo, scientists believe that there is a known rate of mutation in the mitichondrial DNA (the energy cell inside our cells, inherited only from mother). they use it as a clock, to tell the divergence of related species, see below:

    http://www.actionbioscience.org/evolution/ingman.html
    http://mbe.oupjournals.org/cgi/content/abstract/14/3/277
    http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Abstract&list_uids=8920257
    http://www.bioone.org/bioone/?request=get-abstract&issn=0022-2372&volume=085&issue=05&page=0842
     
  21. wesmorris Nerd Overlord - we(s):1 of N Valued Senior Member

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  22. CharonZ Registered Senior Member

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    786
    Actually I have no idea why that was misleading? The so-called junk DNA appears to have so far unknown functions (as e.g. in gene regulation), although some might also be some "left overs" which had no negative impact on the fitness. The article is focused on introns, although introns but there are whole regions which appear to be non-codogenic . As the article implied, newer findings also suggests a functions for these (not only for introns), but I fail to see your proposed directed mutation bit by environmental factors here.
     
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