Manatees by: kathy hufford manatees evolved from four-footed land mammals over 60 million years ago. manatees are distantly related to elephants. they range in color from gray to brown, and the average adult is about 10 feet long and weighs between 1,500 and 2,200 pounds. life expectancy is about 60 years. newborns range in size from 4 to 4.5 feet, and weigh about 60 pounds. manatee young are called calves. what is the best conclusion for this paragraph? a) they are entirely aquatic, meaning they spend their full lives in the water. b) in the u. s. the manatee is listed as a federally endangered species. c) calves are dependent on their mother for up to 2 years. d) they thrive well in fresh, salt and brackish waters.