Asian black bear
Biologically and morphologically, Asiatic black bears represent the beginning of the arboreal specializations attained by sloth bears and sun bears. Asiatic black bears have karyotypes nearly identical to those of the five other ursine bears, and, as is typical in the genus, they have 74 chromosomes. From an evolutionary perspective, Asiatic black bears are the least changed of Old World bears, with certain scientists arguing that it is likely that all other lineages of ursine bear stem from this species. Scientists have proposed that Asiatic black bears are either a surviving, albeit modified, form of "Ursus etruscus", specifically the early, small variety of the Middle Villafranchian (Upper Pliocene to Lower Pleistocene) or a larger form of "Ursus minimus", an extinct species that arose 4,000,000 years ago. With the exception of the age of the bones, it is often difficult to distinguish the remains of "Ursus minimus" with those of modern Asiatic black bears.
Asian black bear
Wildlife Trust of Bangladesh conducted an on field survey of bears in Bangladesh from 2008–2010 that included Asiatic black Bears. The survey was done in 87 different places mostly in north-central, north eastern and south eastern area of Bangladesh that had historical presence of bears. The survey result says that most of the areas still has some isolated small bear populations mainly the Asiatic black bears. According to the survey the most evidence found relating bears were of Asiatic black bears that included nests, footprints, local sighting etc. There are many reports on the presence of Asiatic black bears in central, north-central, north eastern and south eastern parts of Bangladesh.