It seems there are different theories regarding origin and dispersal of Jats.Few links on origin of Jats.
QUOTE
Jat Origins
According to the ancient literature, Jats are the progeny of Aryaputra Bharat. Jats are inherently very hardworking people, and they are considered to be the backbone of Indian agriculture; known for their valor and religious fervor. Jats claim to be the descendants of Chandravamsha, but there are various Jat castes, which claim to be the descendants of Suryavamsha and Agnivamsha. Historically Jats mixed up with the foreign invaders like Sakyas and Huns; but there are exceptions to prove the point against it; the kingdoms of Bharatpur and Dhaulpur are the live examples.
Under the ‘Karna Parva’ of Mahabharata, there is mention about ‘Jarta’, which is indicative of Jats. Panini also used the word ‘Jatta’, which again is indicative of Jats clan. According to historians, approximately 1500 years ago Jats were an affluent class in the northwest frontiers being the ruling class. When Yaduvamshi Bhatis were forced out of Shalivahanpur, the Jats were also compelled to take refuge under the protectorate of Joshya Rajputs. The first know kingdom established by Jats was ‘Derewal’ under Jaisalmer. The land was divided among Jats and Rajputs, but in due course, Rajputs annexed the entire land and Jats were reduced to gypsies; consequently, Jats kept wandering from place to place and their off springs, thus, remained illiterate. They, however, gained expertise in agriculture, which was the mainstay of their livelihood. Leading their life as tribals, the climate had its effect on their nature, thinking, and physical structure. The got mixed up with the local population adopting their customs and religion. Earlier, Jats were confined to Punjab and Sindh only; later, they spread over the Ganges region and Rajasthan. In 1505 AD, Jats supported the invasion by Sikander Lodi in Vamrauli. In reward to their support, Jats were given the kingdom of Mohad, which was later renamed as Dhaulpur in 1806 AD. The second kingdom ruled by Jats was Deem; which later came to be known as Bharatpur in 1723 under the rule of Sinsinvar Jats. Jats fought many battles to maintain their superiority in these kingdoms.
Physically, Jats are well built and sturdy like Rajputs; they are tall, sturdy, having wheatish complexion with a broad forehead and strong arms and broad shoulders. Jats are by nature adamant if they are treated with contempt or injustice; they are more amenable to love and affection; they are independent by nature, self-conscious, and never hesitate to give their life for their self-respect, when needed. They value their self-respect more than anything else
Common Origins of Croats,Serbs & Jats
Couldn't copy,paste from the website
.Genomic diversities and affinities among four endogamous groups of Punjab (India) based on autosomal and mitochondrial DNA polymorphisms
Four endogamous groups of Punjab consisting of Brahmins, Khatris, Jat Sikhs, and Scheduled Castes were studied for eight InDel loci. The Brahmins are geographically distributed over the entire State of Punjab. They are traditionally priests and torch-bearers of Aryan rituals, but now they participate in various, primarily white-collar, occupations. The Khatris occupy the central region of Punjab. Their main occupation is trade. There are some subgroups of this caste. Consanguinity is practiced within the subgroups, but the level of inbreeding is low. Jat Sikhs are predominantly agriculturists and inhabit all regions of the state. They may have entered Punjab after the Brahmins and Khatris (Ibbetson 1916a, b). The Scheduled Castes are primarily menial workers and occupy the lowest rung in the social hierarchy. They also inhabit all regions of the state. According to the Hindu caste system in Punjab, Brahmins are at the top of the social ladder and the Scheduled Castes are at the lowermost rung. The position of Jat Sikhs and Khatris is controversial. According to one view Jat Sikhs are at the top since they are the most predominant caste group ([approximate]60%) among the Sikhs (followers of Sikhism). The social ranking of the Khatris, or the Kshatriyas of the original Manu's classification of castes, is below the Brahmins and just above the Scheduled Castes. The origin of Jat Sikhs is also disputed. While one view is that they are one of the Rajput tribes, another is that the Rajputs belong to the original Aryan stock that entered India, and the Jats belong to a later wave of immigrants of Indo-Scythian stock (Ibbetson 1916a,b). A total of 192 blood samples of unrelated individuals, 48 from each endogamous group belonging to different social strata, were collected randomly from different geographical locations of Punjab, India.
