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For birds, predation linked to faster aging

For birds, predation linked to faster aging

Bird spe­cies that suf­fer from more preda­t­ion tend to age faster, a new study finds. That sup­ports an old the­o­ry in­tend­ed to ex­plain why an­i­mals have such widely var­y­ing life­spans, sci­ent­ists claim.

The re­search­ers could­n't say wheth­er the find­ings might help ex­plain hu­man life­span as well. But it seems to hold “at least in birds, where the nec­es­sary da­ta are avail­a­ble for many spe­cies”-some 1,400 of them, whose longe­vi­ties vary by some 25-fold, ac­cord­ing to a state­ment from the Max Planck In­sti­tute for Or­nith­ol­o­gy in Seewiesen, Germany, where the study was con­ducted.

“We were able to con­firm” the the­o­ry “on a broad geo­graph­i­cal scale,” said Mi­hai Valcu, a co-author of the stu­dy, pub­lished on­line April 25 in the jour­nalEcog­ra­phy.

Some fish, tur­tles or even in­ver­te­brates can live to hun­dreds of years, while the ne­on pyg­my gob­y-a small fish-reaches ripe old age at only 60 days. In birds, par­rots such as the Sulfur-crested cock­a­too can live to over 100 years, while the small Al­len's hum­ming­bird tops out at just four.

The clas­si­cal “evo­lu­tion ary the­o­ry of age­ing,” pro­posed by ev­o­lu­tion­ary bi­ol­o­gist George C. Wil­liams over 50 years ago, claims shorter life­spans will af­flict adult an­i­mals that suf­fer high preda­t­ion, ex­po­sure to par­a­sites and oth­er ran­domly oc­cur­ring events.

One way to look at why, is that na­ture or ev­o­lu­tion won't both­er ex­pend­ing much “ef­fort” to ex­tend the life­span of crea­tures that will probably die young an­y­way. Of course, that's not the real rea­son, as ev­o­lu­tion is­n't con­sid­ered a con­scious pro­cess. Ev­o­lu­tion oc­curs when in­di­vid­u­als have more off­spring than oth­ers as a re­sult of hav­ing more “favora­ble” genes. This lets them spread their favora­ble genes through the popula­t­ion, so that grad­u­al­ly, whole spe­cies change. The way those genes arise in the first place is just as any new genes do: muta­t­ion.


So the ag­ing the­o­ry can be ex­pressed like this: if a spe­cies suf­fers high preda­t­ion or rates of paras­itic at­tack, most in­di­vid­u­als will al­ready be killed be­fore the rare muta­t­ions that cause health­i­er age­ing can make an ev­o­lu­tion­ary dif­fer­ence.

Mi­hai Valcu and Bart Kem­pe­naers from the in­sti­tute used a large da­tabase on es­ti­mates of max­i­mum life-span of bird spe­cies. Us­ing a com­plex sta­tis­ti­cal anal­y­sis they found that max­i­mum longe­vity goes down as the num­ber of pred­a­tor spe­cies with­in the same ar­ea goes up. The rela­t­ion­ship held when oth­er life his­to­ry traits known to in­flu­ence longe­vity, such as size and clutch size, were tak­en in­to ac­count. It al­so held no mat­ter how the anal­y­sis was done: at the spe­cies lev­el, at a fin­er re­gion­al scale (groups of spe­cies with­in a cer­tain ar­e­a) or even when com­par­ing en­tire “biore­gions,” they said.

Source : http://www.world-science.net

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