Results for a 37 marker YDNA test (Kit 14479, FTDNA) are publically available at the FTDNA Cowan Project page, for a person claiming descent from Hugh Cowan (11). Shown below is a comparison of the closest matches for this kit, as of October 2011:
The above results show no certain common ancestor in a meaningful genealogical timeframe, between this descendant of Hugh Cowan and anyone else taking the kit at 37 markers or better as of October 2011.
The nearest match for Kit 14479 [Hugh Cowan (11)] is with Kit 72499. This kit shows a 11/12 match (8.3% dissimiliarity) with the kit for the Hugh Cowan descendant. This match is at the edge of the acceptance criteria. FTDNA characterizes such a match as "probably or possibily related", and recommends upgrading the 12 marker kit to be sure.
The descendant owner of Kit 72499 traces their descent to a John Cowan (1811-1845) of Knockaldie Scotland. Since John Cowan and Hugh Cowan are contemporaries of each other (both flourished about 1800-1840), with one living in America, and the other in Scotland, we would presume that if there is indeed a relatively recent common ancestor, that ancestor lived in Scotland prior to the immigration of Hugh or his immediate ancestors.
Kit 72499 matches up well (as well as can be expected with a 12 marker test) with kits belonging to the Seven Cowan Brothers group. Expansion of this kit to 25 or 37 markers might serve to confirm the connection to the Seven Brothers line, but these matches might also collapse showing no relatively recent common ancestor. Either way, useful information might be gained from an upgrade of Kit 72499.
More distant matches
The results above also show that other Kits in the Seven Cowan Brothers Group, match up with kit 14479, though more distantly. At least superfiscially it seems likely that Hugh Cowan (11) may be kinsman to members of the Seven Brothers, though this kinship relation appears to be at the edge of a genealogically meaningful timeframe.