Boston police are seeking the public’s help in learning the circumstances that led to a man being found beaten and unconscious in Dorchester early Sunday morning with life-threatening injuries. The man was being treated at Boston Medical Center, where he was listed in serious condition, Boston police spokeswoman Katherine Shea said Sunday night. Shea said police discovered the man, whom she described as being in his 30s, near 516 Gallivan Boulevard in Dorchester after receiving a call at 4:15 a.m. Sunday. Shea said police have identified the man, but cannot release his name or place of residence. “At this time, it is unclear how the victim sustained his injuries,” Shea said. “Any information from the public would be helpful.” Authorities asked anyone with information to contact police at 1-800-494-TIPS, or by texting “content” to 27463. Tipsters have the option of remaining anonymous, police said.