Evo­lu­tion­ary trig­ger

Rain­fall vari­a­tions dic­tated species evo­lu­tion and mass ex­tinc­tions

Down to Earth - - EVOLUTION -

Rains pre­date life on Earth, says one of the dom­i­nant the­o­ries about the ori­gin of life. In fact, they have in­flu­enced evo­lu­tion. For in­stance, the Asian mon­soon, which took form around 23 mil­lion years ago,and un­der­went vari­a­tions in in­ten­sity,im­pacted the evo­lu­tion of a group of ro­dents, named Rhi­zomy­i­nae, in the Shi­wa­lik moun­tain range of the Hi­malayas, says a new study. This group of ro­dents in­cludes the Asian bam­boo rats and mole rats.

Ter­res­trial and fresh­wa­ter fos­sils of 38 species, de­posited over mil­lions of years in var­i­ous parts of the moun­tain range in Pak­istan,In­dia,Nepal and Bhutan were an­a­lysed in the study pub­lished on March 11 in Sci­en­tific Re­ports. The study showed that the pe­ri­ods of the weak­en­ing of the mon­soon had a huge im­pact on the evo­lu­tion of the ro­dents.

A species’ skull shape, cheek depth and teeth struc­ture in­di­cate the kind of food avail­able and the veg­e­ta­tion, in turn, shows the strength of the mon­soon. A weak­en­ing of the mon­soon about 10 mil­lion years ago led to sparser veg­e­ta­tion and more open land­scapes, leav­ing the ro­dents open to preda­tors,and making food scarce.This led them to seek shel­ter un­der­ground. Sub­se­quently, th­ese ro­dents evolved to have a skull shape and cheek struc­ture that would en­able them to dig with their jaws, rather than their paws, and to feed on un­der­ground veg­e­ta­tion that used to be drier and coarser than that which is found above the ground. The species that could not adapt be­came ex­tinct. There were also sev­eral in­stances of mi­gra­tion of species to­wards Africa.

The Rhi­zomy­i­nae clade of ro­dents

Newspapers in English

Newspapers from India

© PressReader. All rights reserved.