An anonymous reader quotes a report from The Guardian: The cow could be left as the biggest land mammal on Earth in a few centuries, according to a new study that examines the extinction of large mammals as humans spread around the world. The spread of hominims -- early humans and related species such as Neanderthals -- from Africa thousands of years ago coincided with the extinction of megafauna such as the mammoth, the sabre-toothed tiger and the glyptodon, an armadillo-like creature the size of a car. "There is a very clear pattern of size-biased extinction that follows the migration of hominims out of Africa," the study's lead author, Felisa Smith, of the University of New Mexico, said of the study published in the journal Science on Thursday. Humans apparently targeted big species for meat, while smaller creatures such as rodents escaped, according the report, which examined trends over 125,000 years. In North America, for instance, the mean body mass of land-based mammals has shrunk to 7.6kg (17lb) from 98kg after humans arrived. If the trend continues "the largest mammal on Earth in a few hundred years may well be a domestic cow at about 900kg", the researchers wrote. That would mean the loss of elephants, giraffes and hippos. In March, the world's last male northern white rhino died in Kenya.