Origin of Ayurveda

The exact time of the origin of Ayurveda is not clearly known, but it is thought to be about 5000 years back.
Puranas and Vedas give some information about origin of Ayurveda.

Purana
one of the creation myths is "Ksheera Sagara Mardhana". It is the story of God and demons churned for 'elixir' (Nectar of immortality). From this churning of ocean many things are emerged, they are
Kamadhenu (A holy cow)
Kalpavriksha (Sacred tree)
Goddess Lakshmi (Goddess of prosperity)
The moon
Haalahala (Poison)
Lord Dhanvantari with Nectar in his hand.

Lord Dhanavntari holds Ayurvedic descriptions and some herbs in his hand with Nectar.

Hence Lord Dhanvantari is considered to be the founder and god of Ayurveda.

Veda
There are four Vedas, they are Yajurveda, Samaveda, Atharvanaveda and Rigveda.
Ayurveda is treated as Upaveda of Rigveda.

In Ayurveda there are some Paramparas, they are as follows:
1. Daiva Parampara
2. Rishi Parampara
3. Shaiva Sampradaya

Daiva Parampara
As per Daiva Parampara Ayurveda was created by Lord Brahma. It was an unscripted knowledge which was passed to Daksha Prajapati. Daksha Prajapati is said to be father of Parvathi. Daksha Prajapati obtained knowledge of Ayurveda in the form of shlokas hymned by Lord Brahma, this was written in Sanskrit in a hundred thousand verses. This knowledge of Ayurveda is then passed on to two twin brothers Ashwini Kumaras, popularly known as "Physician of Gods". They further passed it on to Lord of sky Indra.
But during that era diseases and immortality started dominating the planet and the people were badly affected with misseries and diseases. Seeing all these mishappenings and sorrows some of the sages approached to Lord Indra and dictated him about grievances mankind was facing. Then Lord Indra decided to shower them with the knowledge of Ayurveda by which they resolve the problems. A team of scholars were selected under Rishi Bharadwaja and were blessed with the complete knowledge of Ayurveda.
Later Rishi Bharadwaja taught it to his desciple Punarvasu Atreya. Punarvasu Atreya had six desciples named Agnivesha, Bhela, Jatukarna, Parashara, Ksharapani and Harita.
After getting knowledge from Rishi Bharadwaja desciples written their own books, among them Agnivesha's literature was popular and it was called as Agnivesha Tantra. But it was incomplete, Acharya Charaka completed it by adding some more chapters popularly known as Charaka Samhita.

Rishi Parampara
According to this theory, Lord Dhanvantari had the knowledge of Ayurveda and it come to known at the time of Samudra Manthana. Lord Dhanvatari then transferred the knowledge of Ayurveda to his seven desciples, they are Sushruta, Vaitarana, Bambhra, Oupadhaneva, Poushkara, Gopura rakshita and Karaveera. All the desciples written their treatises among them only the book written by Sushruta is available and is called as Sushruta Samhita.

Shaiva Sampradaya
As per Shaiva Sampradaya, Lord Shiva is the founder of Ayurveda. Lord Shiva passed his knowledge of Ayurveda to Parvati, Parvati to Nandi, from Nandi to Agasthya. Later Agasthya passed to Choulasthtya.

So the origin of Ayurveda is not clearly known. But according to information from ancient texts, we can say that, Ayurveda is an ancient and higher knowledge which supports human being to lead a happy life in natural way.