Cow may be biggest mammal if humans keep up extinctions: study

OSLO: The spread of humans around the world from Africa thousands of years ago wiped out big mammals in a shrinking trend that could make the cow the biggest mammal on Earth in a few centuries’ time, a scientific study said on Thursday.

The spread of hominims - early humans and relatives such as Neanderthals - from Africa coincided with the extinction of mammals such as the mammoths, sabre-toothed tiger and 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,” lead author Felisa Smith of the University of New Mexico told Reuters of the study published in the journal Science. Humans apparently targeted big species for meat, while smaller creatures such as rodents escaped, according the report examining trends over 125,000 years.

In North America, for instance, the mean body mass of land-based mammals has shrunk to 7.6 kg (17 lbs) from 98.0 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 900 kg” (2,000 lbs), the U. S. team wrote. That would mean the loss of creatures including elephants, giraffes and hippos.

In March, the world’s last male northern white rhino died in Kenya.

But other research casts doubt on a continued shrinking of mammals, partly because of conservation efforts to stave off threats to wildlife such as climate change, loss of forest habitats and pollution and expanding cities.