For paleozoologists, it is nothing new: pleistocene decreases in fossil records of animals that would be superior to other sizes of their bodies. And along with how migratory movements of the first hominids (human ancestors) have become significant in later years, terrestrial mammals continue to fall sharply. Respectfully, the great ones are dying. Higher evolutionary success of smaller mammals over larger suggests that this selection was not entirely natural. To extinction of the megafauna, people probably had a large share. And if this trend remains in the future, we will probably experience the most noticeable decrease in the average size of terrestrial mammals over the last 45 million years in the following centuries.
"That's when we eradicate giraffes, elephants and rhinoceros," says Felisa Smith, the lead author of a study published in the Science journal. "Because then the largest terrestrial mammal will be the domesticated cow that has spread throughout the world. And it can have a weight of about 900 kilograms. "
Weight loss? No, eradication!
The story of how the Neanderthals went from Africa to the whole world, as though at first sight did not fit the fate of the megafauna (the great mammals). One is experiencing a boom, others fall into oblivion. "But obviously it is related," Smith says. "It is no coincidence that, when the apostles of man appeared, at the same time, sagging tigers, mammoths and glyptodones disappear from history. Just the animals of the size of a car. " Smith assumes that human ancestors were dealing with a megafauna because they considered it either as a competitor, the source of danger, or most likely it was caught as an available source of fatty food.
Only the fastest and most inverted mammals, such as rodents, could survive the predative pressure of the pralide. This is why the average weight of terrestrial mammals has considerably decreased. Example? 125,000 years ago, that is, before the advent of humans, we would count in the North American territory a weighted average of 98 kilograms (the average weight of all mammals living there in the area, from the spring to the mammoth), after weighing the average weight drops to 7.6 kilograms. "And this trend continues," Smith says. "Because the contemporary man is steadily disturbing the structure of ecosystems."
The bigger the better
Not all biologists see it so black. "I do not see such a development as likely, " says Thomas Brooks, Head of the Scientific Council of the International Nature Conservation Union. " Today, on the contrary, they are large animals, such as elephants, which have a greater contribution to nature conservation than the little ones. And nowadays, there are still plenty of animals bigger than a cow (for example an African buffalo or a brown bear) who do not belong among the endangered. " Brooks also points out that the Smith study only speaks of terrestrial mammals. "And even the biggest and heaviest of you live under the sea. And after the ban on hunting today, the population of giant giant is growing in numbers. "
Author: Radomír Dohnal
Source: Ekolist.cz