HU­MANS ARE STILL EVOLV­ING

EVO­LU­TION IS STILL SHAP­ING US AND SCI­EN­TISTS DON’T KNOW WHY

The Gulf Today - Panorama - - SCIENCE - By Lau­rence D. Hurst

Mod­ern medicine’s abil­ity to keep us alive makes it tempt­ing to think hu­man evo­lu­tion may have stopped. Bet­ter health­care dis­rupts a key driv­ing force of evo­lu­tion by keep­ing some peo­ple alive longer, mak­ing them more likely to pass on their genes. But if we look at the rate of our DNA’S evo­lu­tion, we can see that hu­man evo­lu­tion hasn’t stopped — it may even be hap­pen­ing faster than be­fore.

Evo­lu­tion is a grad­ual change to the DNA of a species over many gen­er­a­tions. It can oc­cur by nat­u­ral se­lec­tion, when cer­tain traits cre­ated by ge­netic mu­ta­tions help an or­gan­ism sur­vive or re­pro­duce. Such mu­ta­tions are thus more likely to be passed on to the next gen­er­a­tion, so they in­crease in fre­quency in a pop­u­la­tion. Grad­u­ally, th­ese mu­ta­tions and their as­so­ci­ated traits be­come more com­mon among the whole group.

By look­ing at global stud­ies of our DNA, we can see ev­i­dence that nat­u­ral se­lec­tion has re­cently made changes and con­tin­ues to do so. Though mod­ern health­care frees us from many causes of death, in coun­tries with­out ac­cess to good health­care, pop­u­la­tions are con­tin­u­ing to evolve. Sur­vivors of in­fec­tious disease out­breaks drive nat­u­ral se­lec­tion by giv­ing their ge­netic re­sis­tance to off­spring. Our DNA shows ev­i­dence for re­cent se­lec­tion for re­sis­tance of killer dis­eases like Lassa fever and malaria. Se­lec­tion in re­sponse to

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