Probably the oldest overall is something like wrestling, but of the eastern arts, what would be the oldest that people still practice?
As long as there have been people, there has been wrestling. Nearly every culture has some form of it used for contests internal and external to the group. When we talk about old martial arts, we are talking about wrestling.
In Egypt, the fifteenth tomb of Beni Hassan has a large wall depicting wrestling techniques. At this point we're talking about roughly the 19th to 20th century BCE.
The oldest known proof of the existence of oil-wrestling in Ancient Egypt is found in limestone from the tomb of Ptahhoteb near Saqqara from the fifth dynasty (about 2650 BC) from the same period as the Chafadji-bronze.
In China specifically, there is some evidence that something related to (but probably very different from) modern shuai jiao wrestling called jǐao dǐ (角抵, horn butting) was used in 2697 BCE.
Note, however, that defining "still practice" (as well as "Eastern") is very difficult. People still wrestle using almost certainly the same or very similar techniques as those in ancient China, Nubia, Egypt and Iran. But it is very difficult to establish an unbroken line of teaching the same practice going back even a few hundred years. If that is what one is looking for, the often informal and omnipresent art of wrestling might not satisfy you.
An interesting question, and very difficult to answer. The reason is that, especially among far eastern arts, there were many oral traditions, and poor written documentation... Many arts claim ages that documentation does not really support.
From what we know, codified systems of boxing (striking) and wrestling (grappling) were depicted in the murals of one of the tombs of Beni Hasan in Egypt that are dated to about the 20th century BC. We see similar notations in Gilgamesh epics dating back to about 18th century, moving eastward. The next we really know about from the East is Sun Tzu describing the Art of War in the 6th century BC.
It is likely then that some form of folk wrestling from the Middle East, the Jacket wrestling of the Chinese... It's likely something in this range is the missing link of martial arts, and, while different or evolved, is the oldest extant martial art from the east.
Edit: For the sake of completeness, I feel I should mention this, despite it being difficult to phrase for me... There is a collection of arts (martial, healing, etc.) that combined is claimed to be some 2700 years old (originally written about 700 BC) written in a set of scrolls claiming to be the history of Japan. These scrolls are called Amatsu Tatara Hibumi. Supposedly the martial traditions were added around 500 BC after repelling Malay invaders from Japan...
Personally, I find the whole thing entirely suspect, though numerous Japanese koryu arts do claim ties to the scrolls, though only a few claim to be "masters" – generally, the claim is that XYZ set of techniques ties back to these scrolls (For example, a portion of Kukishin-ryu is claimed to derive from Amatsu Tatara Bumon).
This is about the Bodhidharma Shaolin Kung Fu myth. There is no legitimate evidence for Kung Fu or Shaolin Kung Fu coming from India or Kalari being the oldest martial art or first martial art in the world and wrestling(for example in cave paintings in Mongolia), grappling, stone chinese swords were there in prehistoric times.
Bodhidhadharma taught meditation in China but there is no evidence for him teaching martial arts or self defense. The attribution of Shaolin's martial arts to Bodhidharma has been discounted by several 20th century martial arts historians, first by Tang Hao on the grounds that the Yì Jīn Jīng is a forgery.Huiguang and Sengchou were involved with martial arts before they became two of the very first Shaolin monks, reported as practicing Kung Fu before the arrival of Bodhidharma.
Tang's findings are further supported by the work of Matsuda Takatomo in his book "An Illustrated History of Chinese Martial Arts," published in 1979.Therefore there is no legitimate evidence of Bodhidharma's connection to Chinese Kung Fu or Shaolin Kung Fu.Many historians have proven that there is no evidence that Bodhidharma created Shaolin Kung Fu like , Matsuda Ryuchi, Paul Pelliot, Bernard Faure ,Stanley Henning and Micheal Splessbach, Tenjiku Naranokaku, Tang Ho and Matsuda Takatomo. Matsuda Ryuchi could attest to the existence of the Yijin Jing only as far back as 1827.
In the course of his research, Matsuda Ryuchi found no mention of—let alone attribution to—Bodhidharma in any of the numerous texts written about the Shaolin martial arts before the 19th century.
The Yijin Jing appears to be the source for two other popular Qigong forms which are also attributed to various authors. Both the Eighteen Luohan Hands (also associated with Shaolin) and the Eight Pieces of Brocade (Baduanjin) forms seem like abridged versions of Yijinjing sets. The Baduanjin is sometimes attributed to Yue Fei. Of the many versions of all 3 of the above, some also contain forms from the older Wuqin, or Five Animal Frolics of Hua Tuo.There is lots of info on the internet if you do a google search for Bodhidharma myth or Yijin Jing forgery. Some sources : Wikipedia, A Venerated Forgery: The Daoist Origins of Shaolin's Famous Yijin ,Kenpukan , blackbelt magazine, Kung Fu magazine.
The earliest document I'm aware of is Ch'i Chi-Kuang's "Essentials of the Classic of Pugilism". He studied 16 martial arts and combined them in a 32-step forum for troop training. A number of martial arts can be traced back to that book. Douglas Wile in "Tai Chi Ancestors" makes a good case for the book being one of the foundations of Tai Chi Chuan.
This is a video on the Bodhidharma myth and it also has information on ancient martial arts http://www.youtube.com/watch?v=R6kwYocMnIo
This video shows how old martial arts are and that they have existed since prehistoric times around the world. It shows that there are Chinese martial arts which predate Bodhidharma and the Shaolin Temple. This video debunks the myth that martial arts and Shaolin Kung Fu came from India. It is shown why martial arts would have developed independently in countries and not come from just one country.
The legend goes that in the 6th century A.D., an Indian monk named Bodidharma came to a Shaolin temple in China where he taught the monks - who were in bad shape and had troubles with raiders sometimes - 'something' (either some martial arts or just excercises to increase fitness, body strength and condition) > which became the foundation of Shaolin kungfu. > It spread to other Shaolin temples and > eventually spread through the whole country. Then it spread to the rest of East-Asia.
I believe there are some written documents on this.
Then, there is an old martial art in India called Kalaripayattu. Some or most of the Indian practitioners of this style claim this style was what laid the foundation of Shaolin kungfu.
I guess that we'll never be able to be too certain about it though. What's even harder to say, is how much any living style/martial art is the way it was centuries ago. I personally think that martial arts always keep evolving and changing bit by bit.