http://en.wikipedia.org/wiki/Descent_from_Genghis_Khan#DNA_e...

Zerjal et al. [2003] [6] identified a Y-chromosomal lineage present in about 8% of the men in a large region of Asia (about 0.5% of the men in the world). The paper suggests that the pattern of variation within the lineage is consistent with a hypothesis that it originated in Mongolia about 1,000 years ago (thus several generations prior to the birth of Genghis). Such a spread would be too rapid to have occurred by genetic drift, and must therefore be the result of selection. The authors propose that the lineage is carried by likely male-line descendants of Genghis Khan and his close male relatives, and that it has spread through social selection. Both due to the power that Khan and his direct descendants held and a society which allowed one man to have many children through having multiple wives and widespread rape in conquered cities.[7] According to Family Tree DNA, Genghis Khan is believed to have belonged to Haplogroup C3.

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The Genetic Legacy of the Mongols

http://web.unife.it/progetti/genetica/Giorgio/PDFfiles/ajhg2...

Of course Genghis Khan was unusually prolific, and the direct patrilineal aspect is what makes it special, but you don't have to go far back in time to find an ancestor you share with one in ten people, let alone one in a hundred.

http://tedlab.mit.edu/~dr/Papers/Rohde-MRCA-two.pdf

Now it comes from a computer model, so there could be errors or exceptions— I'm thinking extant uncontacted peoples, here. The model accounted for this possibility, as the paper notes: ...in order for a remote island to affect the MRCA date, it must have been colonized prior to the lineage of the mainland MRCA reaching the source population and it must have remained genetically isolated until very re- cently in order for there to be surviving people with no modern mainland ancestry.

Remember that uncontacted peoples are uncontacted by us; the ones we know of have regular if infrequent contact with other tribes, so if contacted tribes share the MRCA it's quite probable that uncontacted ones do as well. Could there be a cache of 50-100 human beings somewhere on this planet who happen to share an MRCA with us who is older than the one shared by all other living persons, maybe 10,000 years? Sure. But they would be the only ones out of 7 billion.

[1] http://tedlab.mit.edu/~dr/Papers/Rohde-MRCA-two.pdf

The place this really falls down would probably be extremely isolated tribes which have had little if any external contact - there's very few nowadays, but some are remote enough that no pairing has probably happened.

Note that the title assumes just patrilinear descent, so any man that may have had only daughters will not pass on the Y chromosome, though he will still have a non-patrilinear lineage (carried by both sons and daughters).

BTW, what are the main structural differences between strictly male and strictly female lineages?

Haven't been able to find it again, though.

from Google Scholar: http://scholar.google.com/scholar?hl=en&q=all+living+hum...

Another reason to say "direct descendant" instead of just "descendant" is that it makes it clear that there's a blood relation.

"Mr L Prosser was, as they say, only human. In other words he was a carbon-based life form descended from an ape. More specifically he was forty, fat and shabby and worked for the local council. Curiously enough, though he didn't know it, he was also a direct male-line descendant of Genghis Khan, though intervening generations and racial mixing had so juggled his genes that he had no discernible Mongoloid characteristics, and the only vestiges left in Mr L Prosser of his mighty ancestry were a pronounced stoutness about the tum and a predilection for little fur hats.

"...Mr Prosser's mouth opened and closed a couple of times while his mind was for a moment filled with inexplicable but terribly attractive visions of Arthur Dent's house being consumed with fire and Arthur himself running screaming from the blazing ruin with at least three hefty spears protruding from his back. Mr Prosser was often bothered with visions like these and they made him feel very nervous. He stuttered for a moment and then pulled himself together.

"...He saw the bulldozer driver's union representative approaching and let his head sink back and closed his eyes. He was trying to marshal his arguments for proving that he did not now constitute a mental health hazard himself. He was far from certain about this - his mind seemed to be full of noise, horses, smoke, and the stench of blood. This always happened when he felt miserable and put upon, and he had never been able to explain it to himself. In a high dimension of which we know nothing the mighty Khan bellowed with rage, but Mr Prosser only trembled slightly and whimpered. He began to fell little pricks of water behind the eyelids. Bureaucratic cock-ups, angry men lying in the mud, indecipherable strangers handing out inexplicable humiliations and an unidentified army of horsemen laughing at him in his head - what a day."

(Hitchhikers chapter 1)

Sure enough, by clicking through and getting to the real journal article, this is the footnote that accompanies the graph which is duplicated in the Discover article:

  Figure 1 - Median-joining network (Bandelt et al. 1999) 
  representing Y-chromosomal variation within haplogroup C*
  (xC3c). Chromosomes were typed with a minimum of 16 binary 
  markers (Qamar et al. 2002; Zerjal et al. 2002; our 
  unpublished observations), including RPS4Y and M48, to 
  define the lineage C*(xC3c) (Y-Chromosome-Consortium 2002), 
  also known as haplogroup 10, derived for RPS4Y and 
  ancestral for M48. Sixteen Y microsatellites were also 
  typed, but DYS19 was excluded from the network analysis 
  because it is duplicated in haplogroup C. The central star-
  cluster profile is 10-16-25-10-11-13-14-12-11-11-11-12-8-10-
  10, for the loci DYS389I-DYS389b-DYS390-DYS391-DYS392-
  DYS393-DYS388-DYS425-DYS426-DYS434-DYS435-DYS436-DYS437-
  DYS438-DYS439. Circles represent lineages, area is 
  proportional to frequency, and color indicates population 
  of origin. Lines represent microsatellite mutational 
  differences.

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"One particular haplotype within Haplogroup C3 has received a great deal of attention for the possibility that it may represent direct patrilineal descent from Genghis Khan." http://en.wikipedia.org/wiki/Haplogroup_C3_(Y-DNA)

I guess then it is not too uncommon to have some genetic relation to any kind of people if they've lived many hundreds of years ago.

[1] http://en.wikipedia.org/wiki/Genghis_Khan#Religion