I actually wrote a bit about this before, albeit in answer to a different question!

The gist of it is that the vast majority of modern day Asian martial arts that claim to be true to their practical military traditions are most likely not, at least not to any significant degree. Maybe inspiration but most martial arts that claim to be unchanged after hundreds or even thousands of years are probably anything but.

There are notable exceptions but all the 'major' organized martial arts schools, especially those that are geared toward sports, are far and away from what warriors would have been using hundreds of years ago.

Many things that would have been extremely effective on the battlefield or in mortal combat are often considered extreme or even barbaric. Particularly if the martial art in question is pursued as a sport today.

The other reasoning is that much of the time, martial art schools/styles/followings were born during times of peace, in the lull after years of warfare.

Take kendo for example. An extremely challenging sport founded in the Japanese tradition of competitive swordplay. The techniques they use to their advantage in the arena would have had absolutely no place on the battlefield of Sengoku Japan in the 1500s. The forms and styles they practice today definitely take inspiration from storied and famed schools of the sword but even the oldest claims only date to the mid Edo period, about 1650 onwards, approximately 100 years after major warfare had ended in Japan.

Asian martial arts isn't really that well preserved if we look at things in the long run.

Many 'styles' have developed/changed to a great degree or have been lost completely.

It's one of those mystic Oriental myths that kung fu/karate/etc hasn't changed in over 'a thousand years' or other something to that effect.

Some may retain the forms or even some specific techniques but the experience and knowledge of how to apply it in an actual martial situation is often completely unrelated to the modern iteration of many 'martial arts'.

Arguably, the Far East as a whole has done just as terrible a job (or alternatively as good a job) as Europeans at preserving all its martial styles and techniques throughout the centuries.

For example, basically every single Japanese martial art that is well known today (karate, aikido, judo, kendo, kyuudo) has very little to do with how the warriors of ancient and Medieval Japan fought. These may take inspiration from historical warrior practices but in reality are not descended from them in any literal sense.

The one technical exception is jujutsu but jujutsu in its current form only resembles the kind of ground work that was expected of an accomplished Sengoku era warrior.

Interestingly enough, the world of Japanese martial arts has a completely different category for studies of actual martial arts, as in the study of historical teachings of how to kill enemies on a battlefield. Students of these schools are taught as authentically as possible to what a training warrior several hundred years ago would have gone through.

Even so, much of the specifics and details of martial arts of even as recent (relatively speaking) as 500 years ago are very spotty in places. Nevermind 1000 years ago or more.

Chinese martial arts are no exception. As far as I have seen, there are no schools or styles that even try to claim that they teach the martial arts of the Warring States Period (500 BC aprx) or the Tang Dynasty (600-900 AD aprx) , arguably one of greatest the peaks of Chinese military history. Much of spear and pike fighting, only second to the crossbow in importance historically to the Chinese military, has been lost to the ruthless passage of time.

As awesome as kung fu is, it has very little place on a battlefield filled with armored men, some on horseback and others shooting arrows when not trying to impale you on their very long pointy sticks.

Of course, this is not to trivialize hand to hand combat, which was obviously important in actual warfare. Wrestling and grappling happened a lot more in warfare than most people think. War isn't always a stand up fight.

In fact, samurai had to train extensively in wrestling because they often went to ground with their opponents.

Yes, that's right. Counter to popular culture's image of a noble, upstanding loving samurai, the warriors of Japan were more than willing to drag one another through blood, mud and piss to try and get the upper hand in their constant death struggles.

Here we come back to jujutsu, which derives from the techniques and styles of grappling, submissions and ground work that Japanese warriors used against one another when they were rolling around in the dirt trying to brutally murder one another during the 16th century Sengoku Japan.

The main difference between the modern and historical versions of jujutsu is that one or both of these sweaty, angry men would have be armed with knives, trying to fight for an opening to savagely stab their opponent over and over again. Knives are conspicuously lacking in modern day jujutsu.

Personally, I think jujutsu with knives would be more entertaining AND more historically accurate. Double the cultural value, 2 birds 1 stone and what not.

Bottom line is that most modern day martial arts, Far Eastern or European or African, are fairly 'new' and most are not 'martial arts' in a literal sense since most of them were not meant for the historical battlefields some may believe.

Those that aren't new have changed so much from their original forms that they can be reasonably considered to be related but separate, more of a spiritual successor than a true descendant.

Feel free to ask follow up questions!

Side question, to what extent has the growth in the knowledge of human anatomy affected martial arts over time?

Can I reccommend reading Boddhisatva Warriors?...although it is limited to Buddhist and maybe Daoist forms.