How did Earth lose its huge mammals, you’d ask yourself? A new study has answered to this mystery, and it seems that we’re to blame. Well, it wasn’t us who did it, it was our ancestors. In 125,000 years, the mammals have lost their enormous size, ‘shrinking’!
Felisa Smith, paleobiologist at the University of New Mexico has concluded in her study that it was our ancient ancestors that put an end to huge mammals.
Environment and Hunting
After dinosaurs died, mammals were able to grow and get big, said Smith. It didn’t matter if there were big or small animals, all had a surviving chance:
“Taken as a whole, over 65 million years, being large did not increase mammals’ extinction risk. But it did when humans were involved”.
In old fossil records from the last 125,000 years, Smith saw that wherever humans settled, big mammals started going extinct, and that meant humans hunted them “probably because they are tasty” or because they could feed more humans at once. Another cause of big mammals going extinct was that humans burned forests and grassland that were vital to the big mammals and they also competed with other big carnivores for prey, by bringing dogs with them to help at hunting.
There is also the issue of environment, such as erosion of land. Smith explained that:
“When a large animal walks up a hill it zig-zags a lot, whereas a small animal walks up more directly, and that has an impact because water follows those game trails down, so erosion and vegetation and what-not are affected by that”.
Smith has published the study in the journal Science.
The Last Huge Mammals on Earth
Rebecca Terry, paleobiologist at the Oregon State University stated that the new study points to the first evolved humans, that started in Africa and influenced the size of mammals. Then they moved to the New World, says Terry:
“At that point pretty advanced weaponry was definitely present, and the extinctions in the New World in North America and South America were really extreme as a result.”
So, it looks like the Americas housed the last biggest mammals since the lands were last populated by humans.
Imagine that 11,000 years ago, an average sized non-human mammal in North America was almost 200 pounds. Now, it measures almost 15 pounds. Researchers say that the mammals still ‘shrink’ in size!
Andre Blair s is the lead editor for Advocator.ca. He holds a B.A. in Psychology from the University of Toronto, and a Master of Science in Public Health (M.S.P.H.) from the School of Public Health, Department of Health Administration, at the University of North Carolina at Chapel Hill. Andre specializes in environmental health, but writes on a variety of issues.