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furshur
SFN Regular
USA
1536 Posts |
 Posted - 07/06/2006 : 06:51:12 [Permalink]
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quote:
From the journal Nature:
Rohde, Olson and Chang1 address a simple but fascinating question: how far back in time must we go to find an individual who was the ancestor of all present-day humans? After a little consideration, the existence of such an individual (the 'universal ancestor' or, as the authors put it, our 'most recent common ancestor') should not surprise: I have two parents, four grandparents, and the growth in the population of my ancestors is close to exponential as I trace them back in time. This is true for anybody's ancestors, and there must soon be an overlap between the ancestors of two or more randomly chosen individuals
It looks to me that the press has made this seem like we are all directly descended from this one dude. However, the way I read the article in Nature, it is not saying we are direct ancestors of this person but that we are related to this guy. In this context it makes sense - sure the aborigines have been isolate for tens of thousands of years, but they are not anymore. Same thing with polynesia, the remotest parts of Africa and South America. Statistically there is probably no such thing as a true 100% pure blood American Indian, a 100% pure blood Aborigine or a 100% pure blood African. The dilution of the pure blood comes from individuals that have a remote relationship to this common ancestor.
Looking at it this way it is not so surprising or hard to believe. |
If I knew then what I know now then I would know more now than I know. |
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Zebra
Skeptic Friend
USA
354 Posts |
Posted - 07/06/2006 : 12:10:02 [Permalink]
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furshur, how are you picturing "related" as being different from having a direct ancestor in common?
Distant cousins are distant cousins because they share a common ancestor (two, actually - unless they are distant "half-cousins"). It's just that, the more "distant" cousins, the more distant in number of generations the common ancestor is. But it's not like that common ancestor is the only ancestor either of them has, or that person populated the world by himself (what a feat that would be, eh - ). It's just that that person appears somewhere on both of their genealogies. Along with alot of other people who don't overlap in that same generation. But the further back you go, the more people you would find in common. (Like, the parents of the most recent common ancestor. Then the grandparents of the most recent common ancestor. And so on.)
It's not like anyone's saying all people are descended from person X as their single, solo, lone ancestral patriarch or something. (Well, not here at least.) It's just that there are so blasted many of us today, and there were so blasted few people in comparison even just 50 generations ago, that basically any of those people of old who have any descendants have a lot of descendants, and at some point as you go back there has to be a most-recent person (actually, I think it could be more than one in the same generation, gotta think about that) who appears on everyone's genealogy. Again, geographic isolation would hamper the interconnectedness, but all it would take is one parent of one person coming from some other geographic location anytime in someone's genealogy, and the connection to the rest of the world opens right up. Genealogically, that is.
[Edited for clarity, or so the author thinks]
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I think, you know, freedom means freedom for everyone* -Dick Cheney
*some restrictions may apply |
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Zebra
Skeptic Friend
USA
354 Posts |
Posted - 07/06/2006 : 12:32:07 [Permalink]
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Sorry, I think I understand "related" now....
Any aboriginal kid who has "mixed blood" certainly has genealogical connections with a much broader group of people than does his aboriginal grandparent, for example, who is "pure-blood". But that doesn't extend the kid's MRCA on his mom's side, say, to be the MRCA of the pure-bread paternal grandfather. Grandpa has to find his own MRCA with the rest of the world.
The MRCA will be different depending on what group you define; the group "everyone alive on earth now", there would probably be a group including some people who are "pure-blooded" in some aboriginal group that has/had been isolated reproductively, like grandpa above. Their mixed-blood kids or grandkids will have a more recent MRCA with the rest of the world than will true "pure-bloods". But all it would take would be one traveler from elsewhere who entered that isolated pure-blood group 20 or 30 generations ago & reproduces once, even just a one-time visit like rape by a visiting sailor, then generations later that isolated group would likely all have genealogic ties to that one person, and to his/her direct ancestors, and to a more recent MRCA than if that single episode of "mixing" hadn't occurred. |
I think, you know, freedom means freedom for everyone* -Dick Cheney
*some restrictions may apply |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 07/06/2006 : 14:40:10 [Permalink]
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My main problem with any maethematical approach to a scientific question is that it boggles my mind, and leaves me out of the discussion. I remember an article by Robert Heinlein that I read when I was a kid. Heinlein had a very low opinion of anyone who had less math skill than calculus. Since Heinlein was my favorite science fiction author, and I was a mathematical numbskull, I felt shamed and humiliated by his opinion.
I now quote some math quotes:
A mathematician is a blind man in a dark room
looking for a black cat which isn't there
- Charles R. Darwin
As far as the laws of mathematics refer to
reality, they are not certain; and as far as they
are certain, they do not refer to reality
- Albert Einstein
Anyone who cannot cope with mathematics is not
fully human. At best he is a tolerable subhuman
who has learned to wear shoes, bathe and not make
messes in the house.
- Robert A. Heinlein
As long as algebra is taught in school, there will
be prayer in school.
- Cokie Roberts
The mathematical sciences particularly exhibit
order, symmetry, and limitation; and these are the
greatest forms of the beautiful.
- Aristotle
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
| Edited by - HalfMooner on 07/06/2006 14:40:58 |
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Zebra
Skeptic Friend
USA
354 Posts |
Posted - 07/06/2006 : 19:17:12 [Permalink]
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| Math = "The science of patterns", which is way cooler than just trying to tackle an equation and crank out the same answer that the teacher expects. Of course, people don't act just like numbers, but imo it's amazing how a math approach can add another way to view the problem. |
I think, you know, freedom means freedom for everyone* -Dick Cheney
*some restrictions may apply |
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furshur
SFN Regular
USA
1536 Posts |
Posted - 07/07/2006 : 06:57:24 [Permalink]
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quote:
A mathematician is a blind man in a dark room
looking for a black cat which isn't there
- Charles R. Darwin
Holy crap, that's great! 
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If I knew then what I know now then I would know more now than I know. |
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marfknox
SFN Die Hard
USA
3739 Posts |
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BigPapaSmurf
SFN Die Hard
3192 Posts |
Posted - 07/07/2006 : 10:09:40 [Permalink]
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This also is based on the silly assumption that interbreeding was widespread everywhere the euros went which was not the case. I mean the Americas was seperated for over 10k years until the late 1400s or did they just forget about that?
This smells of creationist funk to me. |
"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History
"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 07/07/2006 : 15:07:11 [Permalink]
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quote:
Originally posted by marfknox
quote:
A mathematician is a blind man in a dark room
looking for a black cat which isn't there
- Charles R. Darwin
Ohmagosh - psychics are real: Darwin predicted Dembski! http://en.wikipedia.org/wiki/William_Dembski
I'm sure if we used the same extreme kind of "open-minded" inquiry (in Carl Sagan's sense) employed by many of the readers of Nostradamus and Edgar Cayce, we could find many other such startling prophecies in the writings of the scientists we admire.
Poor Dembski! He's the Winston Smith of the Creationists.
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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