Hu­mans didn’t cause mass an­i­mal ex­tinc­tions, study con­tends

USA TODAY Weekend Extra - - FRONT PAGE - Ash­ley May

A new study dis­agrees with a long­stand­ing view that hu­mans wiped out large an­i­mals that pre­vi­ously oc­cu­pied Africa.

In re­search pub­lished Fri­day in the jour­nal Sci­ence, au­thors an­a­lyzed records on mega­her­bi­vore com­mu­ni­ties in east­ern Africa over 7 mil­lion years. A mega­her­bi­vore is a mam­mal weigh­ing more than 2,000 pounds. They con­cluded that ex­tinc­tions of di­verse mam­mal com­mu­ni­ties in Africa oc­curred be­fore ev­i­dence of hu­man hunt­ing.

The an­i­mal de­cline might have in­stead been be­cause of en­vi­ron­men­tal fac­tors such as de­clin­ing at­mo­spheric car­bon diox­ide and ex­pan­sion of grass­lands, re­searchers write.

“Low CO2 lev­els fa­vor trop­i­cal grasses over trees, and as a con­se­quence sa­van­nas be­came less woody and more open through time,” John Rowan, a post­doc­toral sci­en­tist from the Univer­sity of Mas­sachusetts Amherst who was in­volved in the re­search, said in a state­ment. “We know that many of the ex­tinct mega­her­bi­vores fed on woody veg­e­ta­tion, so they seem to dis­ap­pear along­side their food source.”

Anal­y­sis sug­gests 28 lin­eages of mega­her­bi­vores went ex­tinct, start­ing around 4.6 mil­lion years ago, said lead au­thor Tyler Faith, an as­sis­tant pro­fes­sor in the Depart­ment of An­thro­pol­ogy at the Univer­sity of Utah. To­day, only ele­phants, hip­popota­muses, gi­raffes and white and black rhinoceroses ex­ist.

Univer­sity of Ox­ford, U.K., re­searchers cau­tioned that it isn’t ex­actly clear when hu­mans be­gan af­fect­ing large an­i­mal pop­u­la­tions, but there is strong ev­i­dence that hu­man im­pact played a role in losses tens of thou­sands of years ago.

“The causes of mega­her­bi­vore de­cline are prob­a­bly com­plex, mul­ti­di­men­sional, and var­ied across time and space,” René Bobe and Su­sana Car­valho wrote in the same is­sue of Sci­ence.


A few mega­her­bi­vores still ex­ist, such as ele­phants.

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