The Mesolithic site where three human skeletons were found buried together in the same grave is:

At Damdama, a Mesolithic site in the Pratapgarh district of Uttar Pradesh, a grave containing three human skeletons buried together has been found.

About Damdama:

• It is located in the middle Ganga plain, near a lake formed in an old river channel.
• It was excavated by the University of Allahabad and the Uttar Pradesh State Archaeology Department in the 1980s.
• It is one of the three major Mesolithic sites of the Pratapgarh region, along with Sarai Nahar Rai and Mahadaha.

Burials at Damdama:

• About 40 or more human burials have been found.
• Most burials are single, but some contain two persons, and one grave contains three individuals buried together.
• The dead were usually buried lying on their backs, in an extended position, with heads towards the west.
• Some burials contain grave goods, such as bone ornaments and animal bones.

Other finds:

• Microliths and bone tools.
• Hearths (fireplaces) used for cooking and roasting meat.
• Bones of animals such as wild cattle, deer, wild boar, tortoise and fish, which show that the people were hunters, fishers and food gatherers.
• Grinding stones, which suggest that they also collected wild plants and grains.

About Mesolithic sites of the Ganga plain:

• Sarai Nahar Rai: burials and microliths.
• Mahadaha: burials, and evidence of a lake-side camp.
• The people of these sites were tall and strong, according to studies of their skeletons.
• These sites are among the earliest burials in India.

Why not the other options?

• ✗Bagor is a Mesolithic site in Rajasthan.
• ✗Langhnaj is a Mesolithic site in Gujarat.
• ✗Adamgarh is a Mesolithic site in Madhya Pradesh.