Audi & Wushuer,
Yes indeed, the Wu (吳) family emphasis on wrestling stems from their Manchu heritage. The Manchu (as with related Central Asian peoples such as the Mongolians, Türks and the Japanese) are big on wrestling, to the point that they see it as a defining aspect of their cultural expression.
Wu Ch'uan-yu (吳全佑) and other Manchu Bannermen learned originally from Yang Lu-ch'an, starting in 1850. Wu Ch'uan-yu was only 16 in 1850, so he started training T'ai Chi at a young age (more on this later). In 1870, Wu Ch'uan-yu became a disciple of Yang's son, Yang Pan-hou.
The Wu family's emphasis on wrestling covers all strategic aspects of the activity; tumbling for various distances, righting oneself, jumping from various heights, avoiding weapons, punches and kicks, catching punches and kicks in mid-air, catching punches and kicks and THEN jumping, throws, allowing oneself to be thrown for strategic purposes, footsweeps, locks and breaks, fighting from the ground, on the ground, etc.
What they insist on is that it all be accomplished with T'ai Chi principles. This gives many advantages over hard style grappling. Neutralization, speed, resilience and stamina are all enhanced when "soft" style technique is observed.
It has been explained to me that this emphasis on wrestling is for making sure that the training the students are getting is thorough. If they can neutralize or shield the impact of their entire body weight accelerated into the floor, then they are probably able to neutralize or shield the impact of a simple punch or kick. Generally, this sort of training is only exhaustively undertaken by younger students, older people coming to Wu style training have to get into the wrestling aspect much more selectively, as they don't yet have the resilience of a teen-ager. It does develop over time, but there are some throws and jumps that aren't appropriate for a new 40 year old student to train that a 16 year old would have no problem with. At higher levels of accomplishment, wrestling isn't that necessary, one isn't bound to the philosphy, so to speak. An attacker can be stopped perfectly well with more conventional stand up technique. The Wu family see their wrestling training as a "fast track" to the martial art and that it allows students at an earlier stage of their training to have more options for defending themselves.
From what I've seen of proper Yang family and Ch'en family style (although I've never trained them), there are many forms which are quite suitable for the leverages required in throws, footsweps and other wrestling applications. I'm sure that high level practitioners of those styles are quite capable of dumping their training partners if the mood ever struck them!
[This message has been edited by Polaris (edited 02-16-2004).]